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Calculation of Hydrologic Parameters Using CRWR-PrePro. Francisco Olivera, PhD Center for Research in Water Resources University of Texas at Austin. Hydrologic Parameters. Watershed Abstractions and routing method Parameters Stream Routing method Parameters.
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Calculation of Hydrologic ParametersUsing CRWR-PrePro Francisco Olivera, PhD Center 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 Precipitation (mm) Excess precipitation (mm) Soil properties Excess precipitation = f(Precipitation, Soil properties)
Watershed Routing Excess precipitation (mm/hr) Watershed Runoff flow (m3/s)
Watershed Routing Excess precipitation (mm/hr) Excess precipitation and Runoff flow Runoff flow (m3/s) Time 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
Watershed Lag-Time (SCS) tp: lag-time (min) LW: length of longest flow-path (ft) S: slope of the longest flow-path (%) CN: average Curve Number Dt: analysis time step
Watershed Lag-Time (L/V) tp: watershed lag-time (min) Lw: length of longest flow-path (ft) Vw: longest flow-path average velocity (m/s) Dt: analysis time step
Hydrologic Parameters • Watershed • Abstractions and routing method • Parameters • Stream • Routing method • Parameters
Pure-Lag Method • Flow is delayed a fixed amount of time tlag. tlag: flow time in the reach I: inflow to the reach Q: outflow from the reach
Muskingum Method • Flow is delayed a fixed amount of time K, and redistributed around its centroid. S: storage in the reach K: flow time in the reach (Dt < K < Dt/2X) X: storage parameter I: inflow to the reach Q: outflow from the reach Dt: analysis time step
Routing Method Flow time (Ls/Vs) Ls/Vs < Dt Ls/Vs > Dt Pure LagRouting MuskingumRouting Ls: length of the stream Vs: flow velocity in the stream Dt: analysis time step
Hydrologic Parameters • Watershed • Abstractions and routing method • Parameters • Stream • Routing method • Parameters
Pure Lag Parameters 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-reaches Dt: analysis time step