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					libHydro
    LibHydro


 LibHydro in Excel
 LibHydro in ArcMap
       LibHydro in Excel
Functions list that is called by Excel VBA
              LossGreenAmpt
         The Green and Ampt model computes the precipitation loss on the pervious
         area in a time interval as:
                                                 Ft    S f 
                                         ft  K                
     0              Moisture Content
                                                      Ft       
              Li                              i
                                               ft: Infiltration Rate (L / T)
                     L(t)                      K: Hydraulic Conductivity (L/T)
                                               Ft: Cumulative loss at time t (L)
                                               Sf: Wetting Front Suction Head (L)
                            ft                 ΔΘ :Moisture Deficit (-)
               Φ                               Φ: Porosity (-)
θr
                                               Θi: Initial Moisture Content (-)
               θe
                                       Li: START INITIAL LOSS
         θi          Δθ                L(0): START INFILTRATION
                                       L(END): FINAL INFILTRATION
LossInitialConstant

Basic Concept for LossInitialConstant
    Et = Et (Impervious) + Et (pervious)
          Et (Impervious) = Pt
                              0           if ΣPt < Ia
          Et (pervious) =     Pt – fc     if ΣPt > Ia and Pt > fc
                              0           if ΣPt > Ia and Pt < fc

           Et : Excess at time t
           Pt : Precipitation at time t
           Ia: Initial Loss
           fc: Constant Loss Rate
 LossSCSCurveNumber


        Pe = Accumulated precipitation excess at time t (mm)
        P = Accumulated rainfall depth at time t (mm)
        Ia = Initial abstraction (initial loss) (mm)
        S = Potential maximum retention (mm)




(For SI Unit)
         CN = Curve number (30 < CN < 100)
  Unit hydrograph
      Precipitation (mm)

Loss Rates (Green Ampt, Initial
Constant or SCS Curve Number

                  Excess (mm)
        Unitgraph Size
                  # of unitgraph ordinates
Unitgraph (Snyder, SCS or Clark)
                  Unit Runoff (m3/s per mm of excess)
    Unitgraph Convolution


         Runoff (m3/s)
           Unitgraph Clark
Parameters
 Time of Concentration:
  The time of flow from the farthest point on the watershed to the outlet
 Storage Time:
  Storage constant R with the linear reservoir model
  St = R*Ot

Process of the Unitgraph Clark
  1. Estimate the contribution area with A         t
                                                       1.5
                                                             t
  2. time-area relationship
                                          t
                                             1.414  fort  c
                                                   t 
                                         A          c       2
                                                                                   Ot  C A I t  C B Ot 1
                                                               1.5
                                           At               t               tc
                                               1  1.4141  
                                                          t        fort 
                                           A                c               2             t
                                                                                   CA 
  3. Calculate the average inflow It to the storage at time t                           R  0 .5  t
  4. Calculate the unitgraph ordinates with the following equations                CB  1  C A
                                                                                          Ot 1  Ot
                                                                                   Ot 
                                                                                               2
                                          Snyder’s Unit Hydrograph
Input Variables                                           Output Variable:
    tp : Snyder Lag (hr)                                     unitgraph ordinates (m3/s per mm of excess)
    Cp: Snyder Cp
    A: Basin Area (km2)
    tR: Time interval                                                                         tpR=tp-(tr-tR)/4
Standard UH                                                                                   (when tpR≠5.5tR)
(when tpR=5.5tR)



                                                                    Discharge per unit area
                                tr
                                                                                                    tR
 Discharge per unit area




                                     tp                                                                  tpR
                                              qP=2.75*Cp/tp
                           qp                                                                 qpR                       qPR=qP*tp/tpR
                                                                                                               W75

                                                                                                               W50


                                                                                                               tb
                                           Time                                                                      Time
       SCS Dimensionless Hydrograph

                                          CA        qp: Peak runoff (m3/s)
       Tr                            qp             C:2.08 for SI
                                           Tp        A: Basin Area (km2)
            Excess Rainfall                          Tp: Time of rise
                                           Tr
Tr/2                                Tp        tp   Tr: Excess Duration (hour)
                                            2        Tp: lag time (hour)
              tp
                                     t p  0.6Tc     Tc: Time of concentration (hour)


                              Direct Runoff

                    qp
            Tp
                         tb
         BaseflowHEC1
(A) total flow > recession threshold at falling limb
     or total flow is at rising limb
     Qb  Q0  K t
         Qb: base flow
         Q0: initial base flow
         K: recession constant
         T: time                      Discharge
                   ( t t r )                                         recession
     Qt  Qr  K                                        Total flow    threshold
         Qt: total flow
         Qr: flow where recession starts
         tr: time when recession starts
                                                                     Time
(B) total flow < recession threshold at falling limb

       Qb  Qt  DirectRuno ff                         Baseflow
           Muskingum Routing
                                                Prism Storage
                                                Wedge Storage


St  ( PrismStorage)  (WedgeStorage)
 KOt  KX ( I t  Ot )                 Oi  (ca  cb ) I i 1  cb I i  (1  ca )Oi 1
St  St 1 I t  I t 1 Ot  Ot 1      where
                      
   t           2           2                      2t
                                        ca 
                                             2 K (1  x)  t
        St: Storage at time t
        It: Inflow at time t                   t  2 KX
                                        cb 
        Ot: Outflow at time t                2 K (1  x)  t
        K: Muskingum K
        X: Muskingum X
     Muskingum Routing

Feasible region for         2
Muskingum model parameter

                        t 1
      1      K   1      K
              
   2(1  x) t 2 x
                                0        0.5          1.0
                                         X
                                    Feasible region
EarthDistance in ArcMap
LibHydro in ArcMap
Model Builder Input Box
for LossInitialConstant
Loss Initial Constant
                        Excess with Loss Initial Constant Method

               0.16
               0.14
               0.12
  Height(mm)




                0.1
                                                                                                                                                 Precipitation
               0.08
                                                                                                                                                 Excess
               0.06
               0.04
               0.02
                 0
                                            1:00 AM
                                                      2:00 AM
                                                                3:00 AM
                                                                          4:00 AM
                                                                                    5:00 AM
                                                                                              6:00 AM
                                                                                                        7:00 AM
                                                                                                                  8:00 AM
                                                                                                                            9:00 AM
                      11:00 PM
                                 12:00 AM




                                                                                                                                      10:00 AM
                                                                              time
Model Builder Input Box
for Snyder Unitgraph
                     Snyder Unitgraph

                                     Rainfall and Runoff Time Series
                     0.16                                                                1.6
                     0.14                                                                1.4
                                                                    Precipitation
Precipitation (mm)




                     0.12                                                                1.2




                                                                                               Runoff(cms)
                                                                    Runoff
                      0.1                                                                1
                     0.08                                                                0.8
                     0.06                                                                0.6
                     0.04                                                                0.4
                     0.02                                                                0.2
                       0                                                                  0
                      9:36 PM   12:00 AM   2:24 AM   4:48 AM   7:12 AM   9:36 AM    12:00 PM
                                                      Time
Model Builder Process

				
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posted:12/10/2011
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