Estimation of Changes in Ground Water Storage using Recession curve Method

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					2013



   Estimation of
   Changes in
   Groundwater
   storage using
   Recession cuRve
   Method
   Minor Project Report.




                                  SUJAY RAGHAVENDRA N
       NATIONAL INSTITUTE OF TECHNOLOGY KARNATAKA, SURATHKAL
               M.Tech (Water Resources Engineering & Management)
                            ACKNOWLEDGEMENTS

I am grateful to the Lord Almighty who is the “source of knowledge” and one who guided me
in all aspects to bring out this minor project a successful one.

I express my profound gratitude to my guide Mr Subramanya K, Assistant Professor,
Department of Applied Mechanics and Hydraulics, for his valuable guidance and constant
inspiration during the project work.

I express my sincere gratitude to Dr.Subba Rao, Professor and Head, Department of Applied
Mechanics and Hydraulics for permitting me to carry out the work and for his valuable
suggestions.

I express my gratitude to all my friends for their valuable suggestions and constant help,
which rendered thought this report.




                                            I
                                        ABSTRACT

    The well hydrograph explains the temporal variation of ground water levels of a
particular well expressed in terms of depth to water table from the surface. Falling limb or
recession limb of the well hydrograph mainly explains the rate of withdrawal or out flow
from the effective soil media. The recession limb of the well hydrograph can be very
effectively used to explain the behaviour of subsurface flow. The specific yield can be
determined using the recession limb. A recession equation is developed to predict the water
level below ground level in the well at any particular time period of the dry season provided
there is no other type of withdrawal from the subsurface water.

    The quantification of the recession curve involves the selection of an analytical
expression, derivation of a characteristic recession and optimization of the recession
parameters. A major problem is the high variability encountered in the recession behaviour of
individual segments. The segments represent different stages in the outflow process, and a
physically based short-term or seasonal influence on the recession rate adds to the problem of
deriving a characteristic recession.

    The Groundwater Estimation Committee (GEC) in 1997 recommended that ground water
storage be estimated on ground water level fluctuation and specific yield approach.
For the present study, 11 monitored wells with monthly observations (field monitored); wells
data of one year period is considered. The objective of the present study was to quantify the
sub watershed wise changes in ground water storage by using ground water levels.




                                              II
       Estimation of Changes in Ground Water Storage using Recession curve Method.




                                    CONTENTS

ACKNOWLEDGEMENT.                                                                      I

ABSTRACT.                                                                            II

TABLE OF CONTENTS.                                                                   III

LIST OF FIGURES.                                                                     IV

LIST OF TABLES.                                                                      V

1. INTRODUCTION                                                                           1

2. STUDY AREA                                                                             2

3. METHODOLOGY                                                                            4

   3.1 ESTABLISHMENT OF RECESSION EQUATION                                                4

   3.2 SPECIFIC YIELD FROM RECESSION CURVE                                                4

   3.3 CHANGES IN GROUNDWATER STORAGE                                                     5

4. DATA ANALYSIS AND RESULTS.                                                             6

   4.1 DATA OF WATER TABLE LEVELS OF 11 DIFFERENT WELLS.                               6

   4.2 COMPUTATION OF GROUND WATER STORAGE                                             7

5. CONCLUSIONS                                                                       17

6. REFERENCES.                                                                       17




                                           III
                                             LIST OF FIGURES

Figure 1. Recession curve, period and segment...................................................................... 1
Figure 2. LOCATION MAP .................................................................................................. 3
Figure 3.1Recession Curve with Exponential Trend line for open well-1 ............................... 7
Figure 3.2 Recession Curve with Exponential Trend line for open well-2 .............................. 7
Figure 3.3 Recession Curve with Exponential Trend line for open well-3 .............................. 8
Figure 3.4 Recession Curve with Exponential Trend line for open well-4 .............................. 8
Figure 3.5 Recession Curve with Exponential Trend line for open well-5 .............................. 9
Figure 3.6 Recession Curve with Exponential Trend line for open well-6 .............................. 9
Figure 3.7 Recession Curve with Exponential Trend line for open well-7 ............................ 10
Figure 3.8 Recession Curve with Exponential Trend line for open well-8 ............................ 10
Figure 3.9 Recession Curve with Exponential Trend line for open well-9 ............................ 11
Figure 3.10 Recession Curve with Exponential Trend line for open well-10 ........................ 11
Figure 3.11 Recession Curve with Exponential Trend line for open well-11 ........................ 11




                                                            IV
                                           LIST OF TABLES

Table 1 Details of sub catchment and wetland areas .............................................................. 2
Table 2 Depth of water table below ground level................................................................... 6
Table 3 Values of α and Sy computed from recession curve ................................................. 12
Table 4 Calculation of Depth of fluctuation for well no: 6 of Catchment A ......................... 13
Table 5 Calculation of Change in groundwater storage for well-6 of Catchment A .............. 13
Table 6 Calculation of Depth of fluctuation for well no: 5 of Catchment B.......................... 14
Table 7 Calculation of Change in groundwater storage for well-5 of Catchment B .............. 14
Table 8 Calculation of Depth of fluctuation for well no: 8 ................................................... 15
Table 9 Calculation of Change in groundwater storage for well no: 8 .................................. 15
Table 10 Calculation of Depth of fluctuation for well no: 11 ............................................... 16
Table 11 Calculation of Change in groundwater storage for well no: 11 .............................. 16




                                                         V
        Estimation of Changes in Ground Water Storage using Recession curve Method.



1. INTRODUCTION.
      During dry weather, water stored in the catchment is removed from soil by ground-water
drainage and by evapotranspiration. These processes proceed at different rates in time and
space, and are not readily quantified. The gradual depletion of discharge during periods with
little or no precipitation constitutes the drainage or recession rate, graphically presented as
the recession curve (Fig. 1).
      Generally, a well hydrograph follows a definite trend like stream hydrograph with a peak
followed by a recession limb. The recession limb in a post-recharge period is characterised
by two distinct slopes-one a steep one (from August to October/November) and other a
gentler one (from October/November to June). The steeper limb signifies the quick
dissipation of a major part of recharge during the later part of recharge period itself.




                    Figure 1. Recession curve, period and segment.



Components of the hydrograph

    The hydrograph describes flow as a function of time usually known as a time series of
flow. The interest may lie in the hydrograph of a long period of several years or only few
selected rainfall events of few hours or days. The latter situation frequently occurs in the
development of a rainfall-runoff relationship for a watershed.

It is customary to consider two components of the hydrograph:
1. Direct runoff the flow that results directly from the rainfall event. Usually after
considering the associated losses from the gross rainfall. The volumes of effective rainfall
and the volume of direct runoff should be equal.
2. Base flow that is unrelated to the rainfall event.




                                              1
        Estimation of Changes in Ground Water Storage using Recession curve Method.



     The rainfall-runoff relationship describes the time distribution of direct runoff as a
function of excess rainfall (gross rainfall minus losses). Therefore, in developing the rainfall-
runoff relationship for a watershed based on observed hyetographs and hydrographs, one
must first subtract the base flow from the hydrograph. Even after long periods without rain,
water still flows in many streams and rivers. This flow is the result of seepage from
groundwater aquifers into the stream channel. In larger rivers, base flow can be significant. In
periods without rain, the base flow in a stream will slowly decline as a result of the draw
down of the groundwater aquifers. This phenomenon is called base flow recession. It is often
assumed that base flow declines exponentially. Baseflow separation involves dividing the
hydrograph into a direct runoff component and a base flow component.


2. STUDY AREA.

      The study area is near to coast of Mangalore located at mouth of Gurupur River.
Gandari, Alladangadi and Kalehole are the major tributaries of the Gurupur River. Towards
the east of the catchment, the topography is characterized by the steep hill slopes, in the
middle by lateritic plateaus and towards the west by flat lands. Accordingly, the vegetation
comprises of dense forest in the hilly regions, natural shrubs in the midlands and agricultural
croplands in the topographic laws and valleys.
      Analysis of the imagery of the Indian Remote Sensing Satellite indicates the following
dominant land-uses in the basin: forest (37% of total area), Scrub & barren wasteland (27%)
and agriculture land (40% of the total area). Gurpura River Basin has 2000 ha wetland. Our
study area is situated near the mouth of the river with an area about 192 sq km among that
two sub catchments taken for the study, where the wetlands are present. Details of the areas
are shown in the table 1.



                  Table 1 Details of sub catchment and wetland areas

                    Catchments          Sub catchment          Wetland area
                                         area (sq km)            (sq km)
                  Sub catchment A           10.33                 0.513
                  Sub catchment B           15.20                 0.413




                                               2
      Estimation of Changes in Ground Water Storage using Recession curve Method.




Figure 2. LOCATION MAP



                                         KARNATAKA
                 INDIA




                                  DAKSHINA
                                  KANNADA




                                        SUB BASIN




                                             3
        Estimation of Changes in Ground Water Storage using Recession curve Method.



3. METHODOLOGY

3.1 ESTABLISHMENT OF RECESSION EQUATION

In well hydrographs, the subsequent drawdown of the water table occurs and this continues
for four or five weeks from the peak representing a relatively steep slope of the recession
curve. This is mainly due to the quick response in the top layers of the lateritic formations.

Similar behaviour of the well hydrograph and steam flow hydrographs has leaded the use of
recession equation of the stream flow hydrograph to derive an equation for recession
component of well hydrograph considering the dry period only. Water level below ground
level in the open well at any month during dry period can be predicted by applying recession
model.

The recession model is of the form, h = h*eαt                          (3.1)

Where,
h- Water level below ground surface at time t (m)
h0- Initial water level (m)
α- Recession constant
t- Time (days)


3.2 SPECIFIC YIELD FROM RECESSION CURVE

Estimation of specific yield (Sy) of an area (A) is necessary in order to quantify the amount of
ground water outflow during the Non-monsoon season. In this study an attempt has been
made to estimate an average value of Specific yield by recession curve method for non-
monsoon season.

Specific Yield: It is the ratio of the volume of water that can be drained freely under gravity to
the total volume of the saturated aquifer. The specific yield (Sy) is expressed in %. The
volume of water retained by molecular and surface tension forces, against the force of
gravity, to the total volume of the saturated aquifer is called specific retention. The specific
retention is expressed as %.

Porosity = Specific yield + Specific Retention

Specific yield is determined by knowing the total drawdown during the dry periods and
equating this to the total withdrawal of water from the well during the same period. The
specific yield is determined as the ratio of total recession to the drawdown during this period.
The slope of the recession curve derived for a well is considered as the withdrawal rate for
the well. Hence, Sy is determined from the following equation.



                                                 4
        Estimation of Changes in Ground Water Storage using Recession curve Method.



                                         d*Sy = α*t
                                                   ∗
                                          Sy =                                 (3.2)

Where,
d- Total drawdown (m)
t- Time period (days)
α- Recession constant (m/day)

The specific yield so determined is used in the ground water fluctuation method to determine
the change in ground water storage.


3.3 CHANGES IN GROUNDWATER STORAGE

      Change in groundwater storage describes the difference in groundwater volume
between two time periods. Change in groundwater storage is calculated by multiplying the
difference in groundwater elevation between two monitoring periods, by the area overlying
the groundwater basin, and the average storativity (specific yield in an unconfined aquifer)

     The Ground Water level fluctuation method is to be used for computation of change in
ground water storage. Ground water fluctuation method (As per GEC, 1997 Norms) is an
indirect method for the estimation of recharge for the area, where there is distinct division of
a year in to Non-monsoon season and Monsoon season. Majority of rainfall occurs in the
Monsoon season (80%) than in the Non-monsoon season (20%).

                                          (ΔG) = h × A × Sy                       (3.3)
Where,
ΔG - Change in the Ground water storage (ha-m)
h - Change in Ground Water Fluctuations (m)
A - Area of Influence (ha)
Sy - Specific Yield (%)




                                               5
          Estimation of Changes in Ground Water Storage using Recession curve Method.



4. DATA ANALYSIS AND RESULTS.


4.1 DATA OF WATER TABLE LEVELS OF 11 DIFFERENT WELLS.

     Groundwater levels are one of the key indicators of groundwater basin and aquifer
conditions. Groundwater level data can be used to make interpretations regarding
hydrogeology, groundwater flow, groundwater supply and sustainability, land use, etc.
Groundwater levels fluctuate seasonally due to various inputs and outputs, such as the
amount of precipitation, evapotranspiration, and groundwater pumping. Frequent
groundwater level measurements provide more detail regarding the seasonal groundwater
level fluctuations and aquifer conditions.

Well no                            GROUND WATER TABLE BELOW GROUND LEVEL (m)




                                                                                                                              01-May-07


                                                                                                                                          15-May-07
           01-Nov-06

                       15-Nov-06




                                                                                          01-Mar-07
                                      01-Dec-06




                                                                                                      01-Apr-07


                                                                                                                  15-Apr-07
                                                                              01-Feb-07
                                                  01-Jan-07


                                                              15-Jan-07




   1       0.89        0.86           1.06        1.59        1.63            2.32        2.32        2.77        2.34        2.33        2.43

   2       0.55        0.67           1.18        1.39        1.65            1.98        2.21        3.07        2.83        2.55        2.96

   3         0.4       0.38           0.91        1.51        1.91            2.32        2.59        3.12        3.05        2.46        2.65

   4       3.47        3.75           3.95        4.29        4.47            6.75        5.16          5.2       4.86          4.4       4.45

   5       2.92        3.12           3.37        4.26          4.5           5.12          5.7         6.7       6.97        6.28        6.94

   6       4.69        4.78           5.08          5.4       6.28            6.54          6.7       7.31        6.98          6.7       6.98

   7       4.79        4.62           5.02        5.72        5.82            6.22        6.32        6.48        6.39        6.32        6.51

   8       4.09        4.36           4.85        5.31        5.51            5.79        6.07        6.85        7.09        7.16        7.29

   9       4.55        4.55           4.77        5.12        5.37            5.63        6.09        7.32        7.52        6.65        7.75

   10      2.86        2.91           3.09        3.06        3.22              4.1       4.43        4.63        4.28        3.61        3.74

   11      1.56          2.2            2.3       2.36        2.85            3.25          3.5       2.99        2.88        2.36        2.55



                              Table 2 Depth of water table below ground level


Well hydrograph is drawn for ground water depth taken for post monsoon period from 11
different well located across the study area. It is observed that the recession limb of well


                                                                          6
              Estimation of Changes in Ground Water Storage using Recession curve Method.



hydrograph shows the exponential form, using this function specific yields are calculated &
are given in the table 3, Recession curve with exponential trend lines are shown in the figure
from 3.1 to 3.11 for all wells.

4.2 COMPUTATION OF GROUND WATER STORAGE
4.2.1 Estimation of Specific yield using Recession curve method.

                                                       Time period (days)

                                              0   50         100        150     200   250
                                         0
        Depth of water table bgl (m)




                                        0.5

                                         1

                                        1.5
                                                                                              Well no 1
                                         2

                                        2.5                                                 y = 0.7467e0.0082x
                                                                                               R² = 0.9393
                                         3

                                        3.5


      Figure 3.1 Recession Curve with Exponential Trend line for open well-1



                                                       Time period (days)

                                              0   50          100       150     200   250
                                          0
         Depth of water table bgl (m)




                                        0.5

                                          1

                                        1.5
                                                                                              Well no 2
                                          2

                                        2.5                                                 y = 0.5452e0.0106x
                                                                                               R² = 0.9446
                                          3

                                        3.5


      Figure 3.2 Recession Curve with Exponential Trend line for open well-2




                                                                            7
                    Estimation of Changes in Ground Water Storage using Recession curve Method.




                                                            Time period (days)
                                                  0    50        100         150   200   250
                                              0
           Depth of water table bgl (m)




                                          0.5
                                              1
                                          1.5
                                                                                                    Well no 3
                                              2
                                          2.5                                                   y = 0.2768e0.0196x
                                                                                                   R² = 0.9319
                                              3
                                          3.5



Figure 3.3 Recession Curve with Exponential Trend line for open well-3


                                                              Time period (days)

                                              0       50         100         150   200    250
                                          0
Depth of water table bgl (m)




                                          1
                                          2
                                          3
                                          4                                                          Well no 4
                                          5                                                     y = 3.3349e0.0032x
                                          6                                                        R² = 0.9713
                                          7
                                          8


Figure 3.4 Recession Curve with Exponential Trend line for open well-4




                                                                             8
                                 Estimation of Changes in Ground Water Storage using Recession curve Method.



                                                                     Time period (days)
                                                           0    50         100          150     200    250
                                                       0
                    Depth of water table bgl (m)

                                                       1
                                                       2
                                                       3
                                                       4
                                                                                                                  Well no 5
                                                       5
                                                                                                             y = 2.6847e0.0053x
                                                       6
                                                                                                                 R² = 0.96
                                                       7
                                                       8


Figure 3.5 Recession Curve with Exponential Trend line for open well-5



                                                                     Time period (days)
                                                       0       50          100            150    200    250
                                                   0
Depth of water table bgl (m)




                                                   1
                                                   2
                                                   3
                                                   4                                                               Well no 6
                                                   5                                                          y = 4.4183e0.003x
                                                   6                                                            R² = 0.9433
                                                   7
                                                   8


Figure 3.6 Recession Curve with Exponential Trend line for open well-6




                                                                                          9
                                             Estimation of Changes in Ground Water Storage using Recession curve Method.




                                                                   Time period (days)
                                               0          50           100          150     200        250
                                         0
          Depth of water table bgl (m)




                                         1
                                         2
                                         3
                                                                                                                Well no 7
                                         4
                                         5                                                                   y = 4.5478e0.0023x
                                                                                                                R² = 0.9042
                                         6
                                         7
                                         8

                                   Figure 3.7 Recession Curve with Exponential Trend line for open well-7



                                                               Time period (days)
                                              0          50           100           150   200         250
                                         0
Depth of water table bgl (m)




                                         1

                                         2

                                         3
                                         4
                                                                                                                   Well no 8
                                         5
                                                                                                              y = 4.0103e0.0031x
                                         6
                                                                                                                 R² = 0.9727
                                         7
                                         8

                                   Figure 3.8 Recession Curve with Exponential Trend line for open well-8




                                                                                     10
                                   Estimation of Changes in Ground Water Storage using Recession curve Method.



                                                        Time period (days)
                                        0       50         100          150       200        250
                                  0
   Depth of water table bgl (m)


                                  1
                                  2
                                  3
                                  4
                                                                                                       Well no 9
                                  5
                                  6                                                                y = 4.2947e0.0023x
                                  7
                                                                                                      R² = 0.9719
                                  8
                                  9

                               Figure 3.9 Recession Curve with Exponential Trend line for open well-9
                                                          Time period (days)
                                          0     50         100          150      200        250
                                    0
                                  0.5
Depth of water table bgl (m)




                                    1
                                  1.5
                                    2
                                  2.5                                                                 Well no 10
                                    3
                                                                                                   y = 2.7925e0.0015x
                                  3.5
                                                                                                      R² = 0.9306
                                    4
                                  4.5
                                    5

      Figure 3.10 Recession Curve with Exponential Trend line for open well-10

                                                         Time period (days)
                                            0    50         100         150      200        250
                                      0
Depth of water table bgl (m)




                                  0.5
                                      1
                                  1.5
                                      2
                                                                                                     Well no 11
                                  2.5
                                                                                                   y = 1.6422e0.0054x
                                      3
                                                                                                      R² = 0.9002
                                  3.5
                                      4

      Figure 3.11 Recession Curve with Exponential Trend line for open well-11




                                                                        11
Estimation of Changes in Ground Water Storage using Recession curve Method.




       Table 3 Values of α and Sy computed from recession curve



Well no Drawdown (max-min) Recession constant         time    Specific yield

                 d (m)               α (m/day)       (days)        Sy
                 2.31
  1                                      0.0082        15        0.05325
  2               2.52                   0.0106        15        0.06310
  3               3.52                   0.0196        30        0.16705
                  5.2
  4                                      0.0032        15        0.00923
                  4.02
  5                                      0.0053        15        0.01978
                  2.77
  6                                      0.003         30        0.03249
  7               1.96                   0.0023        30        0.03520
                  4.5
  8                                      0.0031        15        0.01033
                  3.2
  9                                      0.0023        15        0.01078
                  4.6
  10                                     0.0015        15        0.00489
                  5.3
  11                                     0.0054        15        0.01528
                  Average specific yield                         0.03831




                                    12
       Estimation of Changes in Ground Water Storage using Recession curve Method.



     Table 4 Calculation of Depth of fluctuation for well no: 6 of Catchment A



             Month          y      Constant         x       Depth of fluctuation
            Nov 06       4.83439   4.4183          30             0.4161
            Dec 06      5.289665   4.4183          60             0.4553
             Jan 07     5.787816   4.4183          90             0.4982
            Feb 07      6.332879   4.4183          120            0.5451
            Mar 07      6.929274   4.4183          150            0.5964
            Apr 07      7.581833   4.4183          180            0.6526
            May 07      8.295847   4.4183          210            0.7140




Table 5 Calculation of Change in groundwater storage for well-6 of Catchment A


                                                          Change in
                      Specific       Depth of            ground water
       Month           yield        fluctuation             storage        (∆G) mm
       Jun-06         0.03831            0                     0              0
       Jul-06         0.03831            0                     0              0
       Aug-06         0.03831            0                     0              0
       Sep-06         0.03831            0                     0              0
       Oct-06         0.03831            0                     0              0
       Nov-06         0.03831         0.4161                0.0159         15.9408
       Dec-06         0.03831         0.4553                0.0174         17.4425
       Jan-07         0.03831         0.4982                0.0191         19.0860
       Feb-07         0.03831         0.5451                0.0209         20.8828
       Mar-07         0.03831         0.5964                0.0228         22.8481
       Apr-07         0.03831         0.6526                0.0250         25.0011
       May-07         0.03831          0.714                0.0274         27.3533




                                              13
     Estimation of Changes in Ground Water Storage using Recession curve Method.



   Table 6 Calculation of Depth of fluctuation for well no: 5 of Catchment B


          Month         y       Constant        x      Depth of fluctuation
         Nov 06      3.147376    2.6847        30              0.4627
         Dec 06      3.689788    2.6847        60              0.5424
          Jan O7     4.325678    2.6847        90              0.6359
         Feb 07      5.071157    2.6847        120             0.7455
         Mar 07       5.94511    2.6847        150             0.8740
         Apr 07      6.969678    2.6847        180             1.0246
         May 07      8.170818    2.6847        210             1.2011




Table 7 Calculation of Change in groundwater storage for well-5 of Catchment B



                                  Depth of      Change in ground
     Month    Specific yield                                            (∆G) mm
                                 fluctuation     water storage

     Jun-06        0.03831            0                 0                  0
     Jul-06        0.03831            0                 0                  0
     Aug-06        0.03831            0                 0                  0
     Sep-06        0.03831            0                 0                  0
     Oct-06        0.03831            0                 0                  0
     Nov-06        0.03831         0.4627             0.0177            17.7260
     Dec-06        0.03831         0.5524             0.0212            21.1624
     Jan-07        0.03831         0.6359             0.0244            24.3613
     Feb-07        0.03831         0.7455             0.0286            28.5601
     Mar-07        0.03831          0.874             0.0335            33.4829
     Apr-07        0.03831         1.0246             0.0393            39.2524
     May-07        0.03831         1.2011             0.0460            46.0141




                                          14
Estimation of Changes in Ground Water Storage using Recession curve Method.



      Table 8 Calculation of Depth of fluctuation for well no: 8



     Month          y      Constant         x        Depth of fluctuation

     Nov 06     4.401151    4.0103         30               0.3909
     Dec 06     4.830095    4.0103         60               0.4289
     Jan 07     5.300844    4.0103         90               0.4707
     Feb 07     5.817473    4.0103         120              0.5166
     Mar 07     6.384455    4.0103         150              0.5670
     Apr 07     7.006695    4.0103         180              0.6222
     May 07     7.689579    4.0103         210              0.6829



Table 9 Calculation of Change in groundwater storage for well no: 8


              Specific       Depth of            Change in ground
Month                                                                (∆G) mm
               yield        fluctuation           water storage

Jun-06        0.03831            0                      0                   0
Jul-06        0.03831            0                      0                   0
Aug-06        0.03831            0                      0                   0
Sep-06        0.03831            0                      0                   0
Oct-06        0.03831            0                      0                   0
Nov-06        0.03831         0.3909                 0.0150           14.9754
Dec-06        0.03831         0.4289                 0.0164           16.4312
Jan-07        0.03831         0.4707                 0.0180           18.0325
Feb-07        0.03831         0.5166                 0.0198           19.7909
Mar-07        0.03831         0.567                  0.0217           21.7218
Apr-07        0.03831         0.6222                 0.0238           23.8365
May-07        0.03831         0.6829                 0.0262           26.1619




                                      15
 Estimation of Changes in Ground Water Storage using Recession curve Method.



     Table 10 Calculation of Depth of fluctuation for well no: 11



     Month         y       Constant         x         Depth of fluctuation

    Nov 06      1.930998    1.6422         30                0.2888
    Dec 06      2.270583    1.6422         60                0.3396
     Jan 07     2.669889    1.6422         90                0.3993
    Feb 07      3.139416    1.6422         120               0.4695
    Mar 07      3.691514    1.6422         150               0.5521
    Apr 07      4.340705    1.6422         180               0.6492
    May 07      5.104063    1.6422         210               0.7634



Table 11 Calculation of Change in groundwater storage for well no: 11


                              Depth of          Change in ground
Month     Specific yield                                              (∆G) mm
                             fluctuation         water storage

Jun-06        0.03831             0                    0                 0
Jul-06        0.03831             0                    0                 0
Aug-06        0.03831             0                    0                 0
Sep-06        0.03831             0                    0                 0
Oct-06        0.03831             0                    0                 0
Nov-06        0.03831          0.2888               0.0111            11.0639
Dec-06        0.03831          0.3396               0.0130            13.0101
Jan-07        0.03831          0.3993               0.0153            15.2972
Feb-07        0.03831          0.4695               0.0180            17.9865
Mar-07        0.03831          0.5521               0.0212            21.1510
Apr-07        0.03831          0.6492               0.0249            24.8709
May-07        0.03831          0.7634               0.0292            29.2459




                                      16
       Estimation of Changes in Ground Water Storage using Recession curve Method.



5. CONCLUSIONS

 Very less change of groundwater change is observed, it ranges from 15.94 mm in the
  month of Nov, 27.35 mm in the month of may for sub catchment-A and 17.02 mm during
  Nov and 46.01 mm during may for catchment-B
 The GEC, 1997 has recommended the specific yield range of 2 to 4 per cent for the
  lateritic provinces. The currently estimated is being 3.8%.




6. REFERENCES.

  Hall, F.R. (1968). Baseflow recession- “A Review.” water resource. Res., 4(5), 973-983.

  Healy, R.W. and P.G. Cook. 2002. Using groundwater levels to estimate the recharge.
  Hydrogeology Journal, 10 (1): 91-109.

  Kumar C.P.(1997). “Estimation of natural ground water recharge.” ISH J. Hydraulic Eng.,
  3(1). 61-74.

  Groundwater Resource Estimation Committee (GEC). 1997. Water resource estimation
  methodology – 1997. Ministry of Water Resources, Government of India.

  Shevenel, L. (1996). “Analysis of Well Hydrographs In A Karst Aqufer: estimation of
  specific yields and continuum transmissivities.” J.Hydrology., 174:331-355.

  Udayakumar, G.(2008) “Subsurface Barriers For Water Conservation In Lateritic
  Formations” Ph.D. thesis, NITK, Surathkal, India.

  Vaishali, S (2009) “Studied on Saltwater Intrusion In The Coastal Dakshina Kannada
  District”, Karnataka”, Ph.D. thesis, NITK Surathkal, India.




                                           17

				
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