Development of a Hydrologic Model and Estimation of its Parameters Francisco Olivera, Ph.D., P.E. Department of Civil Engineering Texas A&M University.

Development of a Hydrologic Model and Estimation of its Parameters

Francisco Olivera, Ph.D., P.E.Department of Civil Engineering

Texas A&M University

Hydrologic Parameters

Watershed

Abstractions and routing method

Parameters

Stream

Routing method

Parameters

Watershed Abstractions

Precipitation (mm/hr)

Excess precipitation (mm/hr)

Excess precipitation = f(Precipitation, Terrain properties)

Terrain properties

Watershed Abstractions

SCS curve number method

10

CN1000

8.0P

10CN

10002.0P

P

2

e

Pe: cumulative excess precipitation (in)P: cumulative precipitation (in)CN: parameter of infiltration (curve number)

Watershed Abstractions

Initial plus constant loss rate

Pe: cumulative excess precipitation (mm)P: cumulative precipitation (mm)Iloss: initial loss (mm)Closs: constant loss rate (mm/hr)t - t0: time since the beginning of the storm (hrs)

)tt(CI)t(P)t(P 0losslosse

Watershed Routing

Excess precipitation (mm/hr)

Flow (m3/s)

Watershed

Flow = f(Excess precipitation, Watershed geomorphology)

Watershed Routing

Excess precipitation (mm/hr)

Flow (m3/s)

Time

Exce

ss

pre

cipi t

ati

on

Flow

tp

SCS unit hydrograph

tp: watershed lag-time (min)

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 Routing

Excess precipitation (mm/hr)

Flow (m3/s)

Time

Pre

cipit

ati

on

Exce

ss

pre

cipi t

ati

on

Flow

Flow = f(Precipitation, Terrain properties, Watershed geomorphology)

Precipitation (mm/hr)

Hydrologic Parameters

Watershed

Abstractions and routing method

Parameters

Stream

Routing method

Parameters

Watershed Parameters

Area

Abtractions:

SCS curve number method (average curve number)

Linear loss rate (initial and constant loss rate)

Routing

SCS curvilinear unit hydrograph (length and slope of longest flow path, average curve number, average velocity in longest flow path)

Elevation Grid

Flow Length Downstream

Flow Length Upstream

Longest Flow-Path

Flow Length Downstream

to the Watershed Outlet

Flow Length Downstream

to 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 Parameters

Hydrologic Parameters

Watershed

Abstractions and routing method

Parameters

Stream

Routing method

Parameters

Routing Method

Routing Method

Flow time (Ls/Vs)

Ls/Vs < t

Muskingum Routing

Ls/Vs > t

Pure Lag Routing

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

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

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 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

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

Hydrologic Parameters

Watershed

Abstractions and routing method

Parameters

Stream

Routing method

Parameters

Stream Parameters

Length

Routing

Pure lag method (average flow velocity)

Muskingum method (average flow velocity and storage coefficient)

Stream Parameters

Hydrologic Model

HEC-HMS Schematic in ArcView

HEC-HMS Basin File (1)

HEC-HMS Basin File (2)

HEC-HMS Basin File (3)

Basin FileSystem Schematic

Basin FileWatershed Parameters

Basin FileWatershed Parameters

Basin FileStream Parameters

Precipitation File

Control File

Hydrograph Time Table

Hydrograph Summary

Hydrograph Plot