Calculation of Hydrologic ParametersUsing CRWR-PrePro

Francisco Olivera, PhDCenter for Research in Water Resources

University of Texas at Austin

Hydrologic Parameters

Watershed Abstractions and routing

method Parameters

Stream Routing method Parameters

Watershed Abstractionsand Routing Method

Abstractions: precipitation/excess

precipitation transformation

SCS curve number method

Initial loss + constant rate loss

Routing: excess precipitation/runoff flow

transformation

Soil Conservation Service (SCS) synthetic

unit hydrograph

Watershed Abstractions

Soil properties

Precipitation (mm)

Excess precipitation (mm)

Excess precipitation = f(Precipitation, Soil properties)

Watershed Routing

Excess precipitation (mm/hr)

Runoff flow (m3/s)

Watershed

Watershed Routing

Excess precipitation (mm/hr)

Runoff flow (m3/s)

Time

Exce

ss

pre

cip

itati

on

an

d

Ru

noff

flow

Runoff flow = f(Excess precipitation, Watershed hydrologic properties)

Hydrologic Parameters

Watershed Abstractions and routing

method Parameters

Stream Routing method Parameters

Watershed Parameters

Area

Average curve number

Initial + constant rate loss

Length of longest flow-path

Slope of longest flow path

Lag time

Elevation Grid

Flow Length Downstream

Flow Length Upstream

Longest Flow-Path

Flow Length Downstream to the Watershed Outlet

Flow Length Downstreamto the Watershed Outlet

Flow Length Upstreamto the Watershed Divide

Flow Length Upstreamto the Watershed Divide

Watershed Longest Flow-Path

Watershed Longest Flow-Path

Slope of WatershedLongest Flow Path

Watershed Lag-Time (SCS)

t5.3,

S67.31

]9)CN/1000[(Lmaxt

5.0

7.08.0w

p

tp: lag-time (min)LW: length of longest flow-path (ft)S: slope of the longest flow-path (%)CN: average Curve Numbert: analysis time step

Watershed Lag-Time (L/V)

t5.3,

V60

L3048.06.0maxt

w

wp

tp: watershed lag-time (min)Lw: length of longest flow-path (ft)Vw: longest flow-path average velocity (m/s)t: analysis time step

Watershed Parameters

Hydrologic Parameters

Watershed Abstractions and routing method Parameters

Stream Routing method Parameters

Routing Method

Pure-Lag Method

Flow is delayed a fixed amount of time tlag.

)t(I)tt(Q lag

tlag: flow time in the reachI: inflow to the reachQ: outflow from the reach

Muskingum Method

Flow is delayed a fixed amount of time K, and redistributed around its centroid.

QIdt

dSandQ)X1(IXKS

S: storage in the reachK: flow time in the reach (t < K < t/2X)X: storage parameterI: inflow to the reachQ: outflow from the reacht: analysis time step

Routing Method

Flow time (Ls/Vs)

Ls/Vs < t

MuskingumRouting

Ls/Vs > t

Pure LagRouting

Ls: length of the streamVs: flow velocity in the streamt: analysis time step

Hydrologic Parameters

Watershed Abstractions and routing method Parameters

Stream Routing method Parameters

Pure Lag Parameters

s

slag V60

Lt

tlag: flow time in the reach (min)Ls: reach length (m)Vs: reach average velocity (m/s)

Muskingum Parameters

K: flow time in the reach (hr) [Muskingum K]X: storage parameter [Muskingum X]Ls: reach length (m)Vs: reach average velocity (m/s)n: number of sub-reachest: analysis time step

s

s

V3600

LK

1t

V/L)3/1,X2max(intn ss

Stream Parameters