1. libHydro

2. LibHydro
LibHydro in Excel
LibHydro in ArcMap

3. LibHydro in Excel
Functions list that is called by Excel VBA

4. LossGreenAmpt
The Green and Ampt model computes the precipitation loss on the pervious area in a time interval as:
L(t)
Moisture Content Φ θe θr θi Δθ ft Li
ft: Infiltration Rate (L / T)
K: Hydraulic Conductivity (L/T)
Ft: Cumulative loss at time t (L)
Sf: Wetting Front Suction Head (L)
ΔΘ :Moisture Deficit (-)
Φ: Porosity (-)
Θi: Initial Moisture Content (-)
Li: START INITIAL LOSS
L(0): START INFILTRATION
L(END): FINAL INFILTRATION

5. LossInitialConstant Basic Concept for LossInitialConstant
Et = Et (Impervious) + Et (pervious)
Et (Impervious) = Pt
Et (pervious) =
0 if ΣPt < Ia
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

6. 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)

7. Unit hydrograph Precipitation (mm) Loss Rates (Green Ampt, Initial
Unitgraph Size
Unitgraph (Snyder, SCS or Clark)
Unitgraph Convolution
Loss Rates (Green Ampt, Initial
Constant or SCS Curve Number
Excess (mm)
Unit Runoff (m3/s per mm of excess)
Runoff (m3/s)
Precipitation (mm)
# of unitgraph ordinates

8. Unitgraph Clark Parameters Process of the Unitgraph Clark
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
2. time-area relationship
3. Calculate the average inflow It to the storage at time t
4. Calculate the unitgraph ordinates with the following equations

9. Snyder’s Unit Hydrograph
Input Variables
tp : Snyder Lag (hr)
Cp: Snyder Cp
A: Basin Area (km2)
tR: Time interval
Output Variable:
unitgraph ordinates (m3/s per mm of excess)
tpR=tp-(tr-tR)/4
(when tpR≠5.5tR)
Standard UH
(when tpR=5.5tR) tr tR tp
tpR
qP=2.75*Cp/tp
Discharge per unit area
Discharge per unit area qp
qpR
qPR=qP*tp/tpR
W75
W50 tb
Time
Time

10. SCS Dimensionless Hydrograph
qp: Peak runoff (m3/s)
C:2.08 for SI
A: Basin Area (km2)
Tp: Time of rise tp
Tr/2 Tr tb Tp
Excess Rainfall
Direct Runoff qp
Tr: Excess Duration (hour)
Tp: lag time (hour)
Tc: Time of concentration (hour)

11. BaseflowHEC1 total flow > recession threshold at falling limb
or total flow is at rising limb
Qb: base flow
Q0: initial base flow
K: recession constant
T: time
Time
Discharge
Total flow
recession
threshold
Qt: total flow
Qr: flow where recession starts
tr: time when recession starts
(B) total flow < recession threshold at falling limb
Baseflow

12. Muskingum Routing Prism Storage Wedge Storage St: Storage at time t
It: Inflow at time t
Ot: Outflow at time t
K: Muskingum K
X: Muskingum X

13. Muskingum Routing Feasible region for Muskingum model parameter X 2 1
0.5
1.0 X
Feasible region

14. EarthDistance in ArcMap

15. LibHydro in ArcMap

16. Model Builder Input Box for LossInitialConstant

17. Loss Initial Constant

18. Model Builder Input Box for Snyder Unitgraph

19. Snyder Unitgraph

20. Model Builder Process