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					 Reaction Kinetics for Modeling
 Non-Point Source Pollution of
   Nitrate with SWAT Model


      Narula, K.K., and Gosain, A.K
   Indian Institute of Technology Delhi




4th International SWAT Conference
               5th July 2007
         Delft (The Netherlands)
Water resources - vital statistics

Rainfall: 4000 bcm/yr, translates into water resources (~48%),
groundwater recharge (~ 11%).

Water consumers - Agriculture (85%); Domestic (4%)

Availability of water per capita (cu.m/ca/year)
  World: 6700
  North America : > 15,000
  India : ~ 1200
                                     All India cultivated area (1951-1999)
                        220
                        200
                        180
                                                                                                Agriculture
Area cultivated (mha)




                        160
                        140
                        120
                                                                                              Meeting requirements of food
                        100                                                                   grains under limited land and
                         80
                         60                                                                   water conditions
                         40
                         20
                          0                                                                   ….asks for intensification
                              1948
                              1950
                              1952
                              1954
                              1956
                              1958
                              1960
                              1962
                              1964
                              1966
                              1968
                              1970
                              1972
                              1974
                              1976
                              1978
                              1980
                              1982
                              1984
                              1986
                              1988
                              1990
                              1992
                              1994
                              1996
                              1998
                              2000
                              2002
                                                                                              (HYV, crop intensity)
                                                         Year
                                                                                                Food grain yields
                               Gross Area Sow n (mha)           Net Area Sow n (mha)
                                                                       1800
                               Area under HYV (mha)
                                                                                      1600

                                                                                      1400
                                                                                      1200
                                                                   Yield (kg ha -1)




                                                                                      1000
                              Land per capita                                          800
                                                                                       600
                              1950’s: 0.89 ha                                          400
                                                                                       200
                              2000’s: 0.33 ha                                           0
                                                                                             1951
                                                                                             1953
                                                                                             1955
                                                                                             1957
                                                                                             1959
                                                                                             1961
                                                                                             1963
                                                                                             1965
                                                                                             1967
                                                                                             1969
                                                                                             1971
                                                                                             1973
                                                                                             1975
                                                                                             1977
                                                                                             1979
                                                                                             1981
                                                                                             1983
                                                                                             1985
                                                                                             1987
                                                                                             1989
                                                                                             1991
                                                                                             1993
                                                                                             1995
                                                                                             1997
                                                                                             1999
                                                                                                        Year production
                                                                                                        Foodgrain
                                               Fertilizer use and food grain yields
                                   100                                                                           1800
                                   90                                                                            1600
Fertilizer consumption (kg ha-1)




                                   80                                                                            1400
                                   70
                                                                                                                 1200                       Implications of




                                                                                                                        Yield (kg ha -1)
                                   60
                                                                                                                 1000
                                   50
                                                                                                                 800
                                                                                                                                            intensification
                                   40
                                                                                                                 600
                                   30
                                   20                                                                            400

                                   10                                                                            200
                                    0                                                                            0
                                         1951
                                         1953
                                         1955
                                         1957
                                         1959
                                         1961
                                         1963
                                         1965
                                         1967
                                         1969
                                         1971
                                         1973
                                         1975
                                         1977
                                         1979
                                         1981
                                         1983
                                         1985
                                         1987
                                         1989
                                         1991
                                         1993
                                         1995
                                         1997
                                         1999
                                                                 Year
                                              Total fertilizer consumption     Yield of foodgrains
                                                                                                                                           Fertilizer use w ith type
                                                                                                            20
                                                                                                            18
                                                                                         Consumption (MT)   16
                                                                                                            14
                                                                                                            12
                                         Increase in irrigation                                             10
                                                                                                             8
                                         and fertilizer use                                                  6
                                                                                                             4
                                                                                                             2
                                                                                                             0
                                                                                                                 1948
                                                                                                                 1950
                                                                                                                 1952
                                                                                                                 1954
                                                                                                                 1956
                                                                                                                 1958
                                                                                                                 1960
                                                                                                                 1962
                                                                                                                 1964
                                                                                                                 1966
                                                                                                                 1968
                                                                                                                 1970
                                                                                                                 1972
                                                                                                                 1974
                                                                                                                 1976
                                                                                                                 1978
                                                                                                                 1980
                                                                                                                 1982
                                                                                                                 1984
                                                                                                                 1986
                                                                                                                 1988
                                                                                                                 1990
                                                                                                                 1992
                                                                                                                 1994
                                                                                                                 1996
                                                                                                                 1998
                                                                                                                 2000
                                                                                                                 2002
                                                                                                                 2004
                                                                                                                                                         Year

                                                                                                                 Total fertilizer consumption (MT)              Nitrate consumption (MT)
                                                                                                                 Phosphate consumption (MT)                     Potash consumption (MT)
         Impact of excessive use of nitrogenous fertilizers
                              District                    State                          Nitrate (mg l-1)
                              Mathura                     Uttar Pradesh                  279
Groundwater                   Aligarh                     Uttar Pradesh                  270
                              Agra                        Uttar Pradesh                  240
 Drinking water               Mahendragarh                Haryana                        1310
 quality standard for
                              Gurgaon                     Haryana                        722
 nitrates: 45 mg l-1
                              Hisar                       Haryana                        419
                              Ambala                      Haryana                        419
                              Bhatinda                    Punjab                         567
                              Ludhiana                    Punjab                         265
                              Peddavoora                  Andhra Pradesh                 53
                            Source Kansal et al. (1992); CPCB, MINARS (1997)
Surface water
Data generated from its 480 river quality monitoring stations, mean nitrate values
have increased from 0.4 mg l-1 in 1979 to 2.8 mg l-1 in 2000

Nitrate exceedence frequency i.e., %stations reporting nitrates exceeding the
standard, has increased from 2% in 1979 to 10% in the year 2000
          (Source: Analysed from datasets published by CPCB, MINARS Series 1979–2001).
                                 Study area –
                                                                                                      HIMACHA L PRADE SH




                                                                                                             Simla
                                                                                                    So lan                              Uttar ka shi



                                                                                                              Sirmau r              Te hri Garh wa l
                                                                                                                                 UTTARA NCHAL
                                                                                                        HA RYANA
                                                                                                                           Dehra dun
                                                                                                          Yamun a n agar




                                                                                                        UTTAR P RADESH




                                 Upper Yamuna                                                                                                                                                           HIMACHAL PRADESH



                                 river sub basin                                                                                                                                                               Simla
                                                                                                                                                                                                       Solan                                  Uttarkashi



                                                                                                                                                                                                                Sirmaur                  Tehri Garhwal
                                                                                                                                                                                                                                      UTTARANCHAL
                                                                                                                                                                                                          HARYANA                Dehradun
                                                                                                                               Jubbal                                                                      Yamuna nagar
                                                                                                       [
                                                                                                       %




                                                                                                                                                                         s
                                                                    %
                                                                    [




                                                                                                                                                                      on
                                                                        Simla        [
                                                                                     %                                                                                                     Jamunotri




                                                                                                                                                                    rT
                                                                                  Kotkhai                                                                                                    %




                                                                                                                                                                  ve
                                                                                                                                                                  Ri
                                                                                     Chopal




                                                                                                                                                                                       a
                                                                            iri




                                                                                                                                                                                    un
                                                                         G
                                                                                              %
                                                                                              [




                                                                                                                                                                                 am
                                                                        r
                                                                                                                                                                                                           UTTAR PRADESH



                                                                     ve




                                                                                                                                                                               rY
                                                                   Ri
                                                              %
                                                              [




                                                                                                                                                                             ve
                                                           Solan




                                                                                                                                                                             Ri
                                                                                                                                                Chakrata
                                                                                                                                                           [
                                                                                                                                                           %
                                                                                                                                                                                                                          District boundary
                                      Hypsom etric curve                                                                                                   Koti                                                           Catchment boundary
                          6000                                                                     Dakpathar
                                                                                                                                                           [
                                                                                                                                                           %

                          5500                                                                                                                         [
                                                                                                                                                       %
                                                                                                                                                                                                                       Streams
                                                                                     Paonta                                                                             % Mussoorie
                                                                                                                                                                        [
                          5000                                                                 %
                                                                                               [
Elevation (m above msl)




                          4500                                                    Tajewala %
                                                                                           [
                          4000                                                                                             Dehradun %
                                                                                                                                    [
                                                                                                                                                                                  Scale: 1 cm = 14 km
                          3500
                          3000
                          2500
                          2000
                          1500
                          1000
                           500
                            0
                                  0
                                  1
                                  2
                                  2
                                  4
                                  5
                                  6
                                  8
                                  9
                                 10
                                 16
                                 17
                                 19
                                 20
                                 21
                                 31
                                 33
                                 34
                                 36
                                 38
                                 69
                                 72
                                 74
                                 76
                                 78
                                 80
                                 96
                                 97




                                      % catchment area above elevation
                                                                                   Precipitation distribution in the sub basin                                                                                                                                                                                                                                                                               N




                                                                                                                                                                                                                 Kotkhai %                                                                                                                                                       Mussoorie
                                                                                                                                                                                            %
                                                                                                                                                                                                    Sim la   %                 Jubbal
                                                                                                                                                                                                                                                                                                                                     600




                                                                                                                                                                                                                                                                                                                Precipitation (mm)
                                                                                                                                                                                                                                                                                                                                     500
                                                                                                                                                                                                                  Chopal
                                                                                                                                                                                                                       %                                                                                                             400
                                                                                                                                                                                    Solan                                                                                                                                            300
                                                                                                                                                                                    %
                                                                                                                                                                                                                                                                                                                                     200
                                                                                   Sim la
                             400                                                                                                                                                                                                                                                                                                     100
                                                                                                                                                                                        Pachchad                                Chakrata                                                                                               0
                                                                                                                                                                                                                                                              %
 Precipitation (mm)




                                                                                                                                                                                              %




                                                                                                                                                                                                                                                                                                                                                                             April
                                                                                                                                                                                                                                                                                                                                                                  March




                                                                                                                                                                                                                                                                                                                                                                                               June


                                                                                                                                                                                                                                                                                                                                                                                                                  August
                                                                                                                                                                                                                                                                                                                                                                                                                              September
                                                                                                                                                                                                                                                                                                                                                                                                                                              October
                                                                                                                                                                                                                                                                                                                                                                                                                                                        November
                                                                                                                                                                                                                                                                                                                                                                                                                                                                   December
                                                                                                                                                                                                                                                                                                                                                                                     May
                                                                                                                                                                                                                                                                                                                                             January
                                                                                                                                                                                                                                                                                                                                                       February




                                                                                                                                                                                                                                                                                                                                                                                                           July
                             300                                                                                                                                                                                 Jateon
                                                                                                                                                                                                                   %
                                                                                                                                                                                                                                 Koti
                             200                                                                                                                                                                                                                                  %


                                                                                                                                                                                                                               Dakpathar
                             100                                                                                                                                                                                                     %
                                                                                                                                                                                                                                                                               Mussoorie
                                                                                                                                                                                                                                                                                                    %
                                                                                                                                                                                                                   Paonta                                                                                                                        %          Raingage
                              0                                                                                                                                                                                            %
                                                                      April
                                                            March




                                                                                               June


                                                                                                                August
                                                                                                                         September
                                                                                                                                     October
                                                                                                                                                   November
                                                                                                                                                                  December
                                    January
                                                February




                                                                                   May


                                                                                                        July




                                                                                                                                                                                                                  Tajewala                                                                                                           0                      20 Kilometers
                                                                                                                                                                                                                       %
                                                                                                                                                                                                                                                                       Dehradun
                                                                                                                                                                                                                                                                           %




                                                                                                      Sim la                                                                        (a)
                             90                                                                                                                                                                                                                                                                                                          Mussoorie                                                                            (c)




                                                                                                                                                                                                                                 Percentage probability (%)
percentage probability (%)




                             80                                                                                                                                                                                                                                       90
                             70                                                                                                                                                                                                                                       80
                             60                                                                                                                                                                                                                                       70
                                                                                                                                                                                                                                                                      60
                             50                                                                                                                                                                                                                                       50
                             40                                                                                                                                                                                                                                       40
                             30                                                                                                                                                                                                                                       30
                             20                                                                                                                                                                                                                                       20
                             10                                                                                                                                                                                                                                       10
                              0                                                                                                                                                                                                                                        0




                                                                                                                                                                                                                                                                                                                          April
                                                                                                                                                                                                                                                                                                        March




                                                                                                                                                                                                                                                                                                                                                        June




                                                                                                                                                                                                                                                                                                                                                                                      August

                                                                                                                                                                                                                                                                                                                                                                                                      September

                                                                                                                                                                                                                                                                                                                                                                                                                    October

                                                                                                                                                                                                                                                                                                                                                                                                                                          November
                                                                                                                                                                                                                                                                               January

                                                                                                                                                                                                                                                                                         February




                                                                                                                                                                                                                                                                                                                                           May




                                                                                                                                                                                                                                                                                                                                                                          July
                                                                          A pril




                                                                                                                         A ugust
                                                              March




                                                                                                      June




                                                                                                                                       September

                                                                                                                                                        October

                                                                                                                                                                         November

                                                                                                                                                                                         December
                                   January

                                                 February




                                                                                         May



                                                                                                               July




                                                                                                                                                                                                                                                                                          % w et days
                                              % w et days
                                                                                                                                                                                                                                                                                          w et day after w et day (% of total days)
                                              w et day after w et day (% of total days)
                                                                                                                                                                                                                                                                                          w et day after w et day (% of total w et days)
                                              w et day after w et day (% of total w et days)
                                                                                                                               N




                                                                                                  1
                                                                                     3


                                              5                                                            2
               Kotkhai                 %
    %                                                                                    4
                   %
                                     Jubbal
                                                                        6
                                                               Tuini
                             %
                                                          #
                              7

                       Chopal                                                                         10
%   Yashwantnagar                                                                9
    #   13

                                                           8
                                                                                     # Damta
                            11
Pachchad       14
                                                  %
    %
                                                                            15
                        %              17
               Jateon
              18                                      %
                                                               19

                                              %       20
                                                                    #                        16

                                                                                                      # Runoff gages
                        Paonta                             Lakhwar                   %                 Streams
                                 %                                                                Sub catchments
                                                                                                       Tons sub catchment
                                                                                                       Lakhwar sub catchment
                            %                                                                          Giri sub catchment
                                                                    %                    0                     30 Kilometers
   Subject area                            Data basis                                Source and map scale
Basic data            Boundaries of the river basin, administrative            Survey of India (SoI); 1: 50 000
                      boundaries, stream networks
Climatic data         Mean monthly and daily precipitation, maximum            Indian Meteorological Department
                      and minimum temperature, solar radiation, wind           (IMD)
                      speed, potential evaporation

Soil-physical data    Soil characterstics (% silt, sand, clay, rocks), field   National Bureau of Soil Survey and
                      capacity, wilting point, hydraulic conductivity,         Land use planning (NBSS& LUP);
                      depth to water table, properties for different soil      1:250 000
                      layers varying with depth
Landuse data          Ground cover                                             SoI, Satellite Imageries, State
                                                                               Agricultural Board
                                                                               1:50 000 and 1:250 000
Hydrogeological       Groundwater-bearing lithologic units,                    Geological Survey of India (GSI);
data and              transmissivity, hydraulic conductivity, groundwater      National       Thematic      Map
groundwater           levels, fluctuations, hydrochemical data, water use      Organization (NATMO), CGWB,
fluctuation           (pumping and extraction)                                 SGWB, 1: 250 000

Topography data       Elevation contours                                       SoI; 1: 50 000
Gauge data            Daily river flows                                        Chander et al. (1984), Central Water
                                                                               Commission, Ministry of Water
                                                                               Resources
Crop and fertilizer   Nitrogenous fertilizers use, crop yields and types of    Fertilizer   Statistics,   Fertilizer
data                  crops; gross and net cropped areas                       Association of India (FAI)
Water quality data    Surface water quality (Nitrate concentrations),          Central Pollution Control Board
                      ground water quality (nitrate concentrations)            (CPCB); State PCB, Station-wise
                                                                               data
                                                                                                                                                 Results of SWAT
                                                                                                                                 Daily stream flow (Dam ta upstream station)
                                800
                                700
                                600
                        ecs)




                                500
               Flow (cum




                                400
                                300
                                200
                                100
                                     0
                                         06161976

                                                    07191976

                                                               08211976

                                                                          09231976

                                                                                     10261976

                                                                                                11281976

                                                                                                           12311976

                                                                                                                      02021977

                                                                                                                                  03071977

                                                                                                                                             04091977

                                                                                                                                                         05121977

                                                                                                                                                                    06141977

                                                                                                                                                                               07171977

                                                                                                                                                                                          08191977

                                                                                                                                                                                                     09211977

                                                                                                                                                                                                                 10241977

                                                                                                                                                                                                                            11261977

                                                                                                                                                                                                                                        12291977

                                                                                                                                                                                                                                                   01311978

                                                                                                                                                                                                                                                              03051978

                                                                                                                                                                                                                                                                          04071978

                                                                                                                                                                                                                                                                                     05101978

                                                                                                                                                                                                                                                                                                06121978

                                                                                                                                                                                                                                                                                                           07151978

                                                                                                                                                                                                                                                                                                                      08171978

                                                                                                                                                                                                                                                                                                                                 09191978

                                                                                                                                                                                                                                                                                                                                            10221978

                                                                                                                                                                                                                                                                                                                                                       11241978

                                                                                                                                                                                                                                                                                                                                                                  12271978
                                                                                                                                                                                     Date (mmddyy)
                                Simulated flow s                                        Observed flow s
                                 Scatterplot of observed and sim ulated daily flow s
                                w ith the SWAT m odel (1976 to 1978, Dam ta upstream
                                                      station)
                               800
                                                                                                                                                                                                                Sub-basin                                                Damta upstream station
Observed flow s (cumecs)




                               600
                                                                                                                                                                                          R2 (daily)                                                                                            0.7248
                                                                                                                                  2
                                                                                                                                 R = 0.7248

                               400
                                                                                                                                                                                          Nash                   and                   Sutcliffe                                                0.7104

                               200                                                                                                                                                        coefficient (daily)


                                 0
                                     0                         200           400           600                                                          800
                                                                 Simulated flow s (cumecs)
                                                                                                                                                              Daily stream flow (Lakhw ar station)
                                              1600
                                              1400
                                              1200
                          Flow (cumecs)


                                              1000
                                              800
                                              600
                                              400
                                              200
                                                  0
                                                      01011976
                                                                 02051976
                                                                            03111976
                                                                                       04151976
                                                                                                   05201976
                                                                                                              06241976
                                                                                                                          07291976
                                                                                                                                     09021976
                                                                                                                                                10071976
                                                                                                                                                            11111976
                                                                                                                                                                       12161976
                                                                                                                                                                                  01201977
                                                                                                                                                                                             02241977
                                                                                                                                                                                                        03311977
                                                                                                                                                                                                                   05051977
                                                                                                                                                                                                                              06091977
                                                                                                                                                                                                                                         07141977
                                                                                                                                                                                                                                                    08181977
                                                                                                                                                                                                                                                               09221977
                                                                                                                                                                                                                                                                          10271977
                                                                                                                                                                                                                                                                                     12011977
                                                                                                                                                                                                                                                                                                01051978
                                                                                                                                                                                                                                                                                                           02091978
                                                                                                                                                                                                                                                                                                                      03161978
                                                                                                                                                                                                                                                                                                                                 04201978
                                                                                                                                                                                                                                                                                                                                            05251978
                                                                                                                                                                                                                                                                                                                                                       06291978
                                                                                                                                                                                                                                                                                                                                                                   08031978
                                                                                                                                                                                                                                                                                                                                                                              09071978
                                                                                                                                                                                                                                                                                                                                                                                         10121978
                                                                                                                                                                                                                                                                                                                                                                                                    11161978
                                                                                                                                                                                                                                                                                                                                                                                                               12211978
                                                  Simulated runoff                                                       Observed runoff                                                                                          Date

                                               Scatterplot of observed and sim ulated daily
                                                flow s w ith the SWAT m odel (1976 to 1978,
                                                              Lakhw ar station)
                          1600                                                                                                                                                                                                                 Sub-basin                                                                                    Lakhwar station
                                                                                                                             1:1
Observed flows (cumecs)




                          1200                                                                                                                                                                  R2 (daily)                                                                                                                                                        0.7717

                           800                                                                                                                                                                  Nash and Sutcliffe coefficient (daily)                                                                                                                            0.7417
                                                                                                                         R 2 = 0.7717

                           400



                                          0
                                              0                    400                            800                       1200                           1600
                                                                 Simulated flows (cumecs)
                                                                                                                                   Nitrate loads in surface w ater (Lakhw ar)
                      1800                                                                                                                                                                                                                                                                                 70000

                      1600
                                                                                                                                                                                                                                                                                                           60000
                      1400
Daily flow (cumecs)                                                                                                                                                                                                                                                                                        50000




                                                                                                                                                                                                                                                                                                                   Daily load (kg/ day)
                      1200

                      1000                                                                                                                                                                                                                                                                                 40000

                      800                                                                                                                                                                                                                                                                                  30000
                      600
                                                                                                                                                                                                                                                                                                           20000
                      400
                                                                                                                                                                                                                                                                                                           10000
                      200

                        0                                                                                                                                                                                                                                                                                  0
                             01011976

                                        02201976

                                                     04101976

                                                                                      05301976

                                                                                                  07191976

                                                                                                             09071976

                                                                                                                        10271976

                                                                                                                                     12161976

                                                                                                                                                02041977

                                                                                                                                                           03261977

                                                                                                                                                                      05151977

                                                                                                                                                                                  07041977

                                                                                                                                                                                             08231977

                                                                                                                                                                                                        10121977

                                                                                                                                                                                                                   12011977

                                                                                                                                                                                                                              01201978

                                                                                                                                                                                                                                         03111978

                                                                                                                                                                                                                                                    04301978

                                                                                                                                                                                                                                                               06191978

                                                                                                                                                                                                                                                                          08081978

                                                                                                                                                                                                                                                                                     09271978

                                                                                                                                                                                                                                                                                                11161978
                                                                                                                                                                                 Date

                                                                                                                                   Daily flow s (cumecs)                                                Daily nitrate load (kg/day)


                                                                                                                                       Nitrate concentration at Lakhw ar
                                                                                  6

                                                                                  5
                                                   Nitrate concentration (mg/l)




                                                                                  4

                                                                                  3

                                                                                  2

                                                                                  1

                                                                                  0
                                                                                                 1976 - OB                         1976-SIM                       1977-OB                      1977-SIM                       1978-OB                          1978-SIM

                                                   Maximum value for the year                                                                     Minimum value for the year                                          Mean daily value for the year
                                                                                                                       Nitrate loads in surface water (Giri at Yashwantnagar)
                      1000                                                                                                                                                                                                                                                                                   30000
                      900




                                                                                                                                                                                                                                                                                                                     Daily nitrate load (kg/day)
                      800                                                                                                                                                                                                                                                                                    25000
Daily flow (cumecs)   700                                                                                                                                                                                                                                                                                    20000
                      600
                      500                                                                                                                                                                                                                                                                                    15000
                      400
                      300                                                                                                                                                                                                                                                                                    10000

                      200                                                                                                                                                                                                                                                                                    5000
                      100
                        0                                                                                                                                                                                                                                                                                    0
                             01011976

                                        02201976

                                                   04101976

                                                                                      05301976

                                                                                                 07211976

                                                                                                            09271976

                                                                                                                         11161976

                                                                                                                                     01051977

                                                                                                                                                 02241977

                                                                                                                                                            04151977

                                                                                                                                                                       06041977

                                                                                                                                                                                  07251977

                                                                                                                                                                                               09151977

                                                                                                                                                                                                          11041977

                                                                                                                                                                                                                     12241977

                                                                                                                                                                                                                                02121978

                                                                                                                                                                                                                                           04031978

                                                                                                                                                                                                                                                      05231978

                                                                                                                                                                                                                                                                 07131978

                                                                                                                                                                                                                                                                            09061978

                                                                                                                                                                                                                                                                                       10261978

                                                                                                                                                                                                                                                                                                  12151978
                                                                                                                                                                              Date

                                                                                                                       Daily flow (cumecs)                                        Daily nitrate load (kg/day)


                                                                                                                           Nitrate concentration at Yashw antnagar
                                                                                          5
                                                                                      4.5
                                                       Nitrate concentration (mg/l)




                                                                                          4
                                                                                      3.5
                                                                                          3
                                                                                      2.5
                                                                                          2
                                                                                      1.5
                                                                                          1
                                                                                      0.5
                                                                                          0
                                                                                                  1976 - OB                         1976-SIM                1977-OB                          1977-SIM                1978-OB                      1978-SIM

                                                     Maximum value for the year                                                                 Minimum value for the year                                   Mean daily value for the year
    Summary of the results
The study has been successful in calibrating and validating
the model consisting of the following components,
   Streamflow
   Groundwater levels
   Nitrates in surface water
The simulated nitrate concentrations show a deviation from
the observed values
The model requires studying nitrate transformation
processes in the unsaturated zone of the soil matrix since
these have a direct bearing on nitrate transport in surface and
groundwater
Review of various models shows that Michaelis-Menten
kinetics, a mixed-order kinetics, is well suited for simulating
microbial action and growth under the influence of various
environmental conditions and substrate concentration
         This aspect has been studied further
  Field tests for examining the kinetics
          Parameter              Unit         Entisol     Anthrosol
Organic matter               g kg-1     2.9             11.8
Total N                      g kg-1     0.2             0.8
NH4+                         mg kg-1    8.2             2.3
NO3-                         mg kg-1    11.5            9.2
pH                                      8.3             8.1
Water holding capacity       %          22.5            23
Density                      g cm-3     1.1             1.2
Particle size distribution
Sand (2–0.02 mm)             %          68.9            27.5
Silt (0.02–0.002 mm)         %          24.6            49.0
Clay (<0.002 mm)             %          6.5             23.5
                                       Simulation results and comparison of kinetics
                                       Sim ulation of nitrification using published data                                                                                            Simulation of nitrification in Anthrosols
             16.0                                                                                                               6.0

             14.0
                                                                                                                                5.0
             12.0
                                                                                                                                4.0
             10.0
N (g/ sqm)




                                                                                                                   N (g/ sqm)
              8.0
                                                                                                                                3.0
              6.0
                                                                                                                                2.0
              4.0

              2.0                                                                                                               1.0

              0.0
                     1       2          3        4       5          6          7       8   9       10       11                  0.0
                                                                                                                                      1       2                                 3            4         5         6         7         8        9
                                                               Time (days)
                                                                                                                                                                                                          e
                                                                                                                                                                                                       Tim (Days)
                     NH4+: Michaelis                         NH4+: SWAT                        NH4+: Observed
                     NO3-: Observed                          NO3-: Michaelis                   NO3-: SWAT                                 NO3-: Michaelis menten                                           NO3-: SWAT               NO3-: Observed

                                                                                                                                                                            Scatterplot of observed and sim ulated nitrates due
                                                                                                                                                                                               to nitrification
                                                                                                                                                                           16

                                                                                                                                                                           14
                                                                                     2
                    Experimental station                                           R           Nash and Sutcliffe                                                          12




                                                                                                                                               Simulated nitrate (g/sqm)
                                                                                                                                                                                             R2 (SWAT) = 0.75
       SWAT (Entisol)                                                              0.75                     0.83                                                           10

                                                                                                                                                                            8

       Michaelis-Menten (Entisol)                                                  0.98                     0.98                                                            6
                                                                                                                                                                                                                     R2 (Michaelis) = 0.98
                                                                                                                                                                            4

       SWAT (Anthrosol)                                                            0.85                     0.90                                                            2

                                                                                                                                                                            0
       Michaelis-Menten (Anthrosol)                                                0.96                     0.98                                                                0                   5                  10
                                                                                                                                                                                                   Observed nitrate (g/sqm)
                                                                                                                                                                                                                                             15



                                                                                                                                                                                       SWAT                    Proposed Michaelis menten
                                         …..simulation results and comparison of kinetics
                                                                                                                                                      Scatterplot of observed and simulated N loss
                                                                                                                                                                                    θ
                                                                                                                                                           due to denitrification (SW < 0.95 FC)
                                                                                                                                        10
                                                                                                                                                                             Case 2
                                          Sim ulation results on influence of soil m oisture on                                              9

                                                             denitrification                                                                 8




                                                                                                                      Simulated N loss (%)
                                                                                                                                             7
                                   70
     N loss (as % of added NO3-)




                                                                                                                                             6
                                   60                                                                                                        5
                                   50                                                                                                        4
                                   40                                                                                                        3
                                                                                                                                                                                R2 (Michaelis) = 0.967
                                   30                                                                                                        2
                                                                                                                                             1                       SWAT does not model for SW<0.95
                                   20
                                                                                                                                             0
                                   10                                                                                                            0     1       2     3    4    5     6    7       8    9      10
                                                                                                                                                                         Observed N loss (%)
                                   0
                                                                                                                                                                   Simulated - Michaelis menten
                                         1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
                                                        Time (days)                                                                                   Scatterplot of observed and simulated N loss
                                                                                                                                                           due to denitrification (SW > 0.95 FC)
                                                                                                                                                                                     θ
                                                                                                                                             52
                                        75%moisture-michaelis                        100%moisture-michaelis                                  48
                                                                                                                                                                              Case 1
                                                                                                                                             44
                                        100%moisture-SWAT                            75%moisture-Observed
                                                                                                                                             40




                                                                                                                      Simulated N loss (%)
                                                                                                                                                           R2 (SWAT) = 0.93
                                        100%moisture-Observed                                                                                36
                                                                                                                                             32
                                                                                                                                             28
                                                                                                                                             24
                                                                                                                                             20
   Experimental station                                                    R2                    Nash and Sutcliffe                          16
                                                                                                                                                                                      R2 (Michaelis) = 0.97
                                                                                                                                             12
SWAT, Case 1; (Case 2)                                          0.93; (does not simulate)     0.86; (does not simulate)                       8
                                                                                                                                              4
Michaelis-Menten,                              Case    1;             0.97; (0.97)                  0.96; (0.96)                              0
(Case 2)                                                                                                                                          0    4   8       12 16 20 24 28 32 36 40 44 48 52
                                                                                                                                                                        Observed N loss (%)

                                                                                                                                                      Simulated - michaelis menten          Simulated - SWAT
                Conclusions
Nitrate transport to surface water and groundwater aquifers
takes place under the influence of the runoff components of
the land phase of the hydrological cycle.

The kinetics of nitrate transformation processes namely,
nitrification and denitrification, in the land phase of the
hydrological cycle determines the transformation and release
of nitrates in surface and groundwater aquifers

The transformation of nitrates is governed by bacteriological
action, which can be best represented by mixed order kinetics
i.e., Michaelis Menten Kinetics

The comparison of the existing first-order kinetics with the
proposed Michaelis-Menten mixed order kinetics indicates
that Michaelis-Menten mixed order kinetics represents the
nitrate transformation processes better
  Limitations of the study

A longer length of record would have been
desirable for calibration and validation of
various components of the integrated model

Nitrate concentration data for surface water was
limited

Fertilizer application data was limited
     Future scope of research

The Michaelis-Menten mixed order kinetics has
been successfully tested using published
experimental datasets. Incorporating it in the
SWAT model itself and simulating nitrate
transformations could be done in the future
thank you

				
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