Calculation of Hydrologic Parameters Using CRWR-PrePro Francisco Olivera, PhD Center for Research in Water Resources University of Texas at Austin

Hydrologic Parameters zWatershed yAbstractions and routing method yParameters zStream yRouting method yParameters

Watershed Abstractions and Routing Method zAbstractions: precipitation/excess precipitation transformation ySCS curve number method yInitial loss + constant rate loss zRouting: excess precipitation/runoff flow transformation ySoil 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 (m 3 /s) Watershed

Watershed Routing Excess precipitation (mm/hr) Runoff flow (m 3 /s) Time Excess precipitation and Runoff flow Runoff flow = f(Excess precipitation, Watershed hydrologic properties)

Hydrologic Parameters zWatershed yAbstractions and routing method yParameters zStream yRouting method yParameters

Watershed Parameters zArea zAverage curve number zInitial + constant rate loss zLength of longest flow-path zSlope of longest flow path zLag time

Elevation Grid

Flow Length Downstream

Flow Length Upstream

Longest Flow-Path

Flow Length Downstream to the Watershed Outlet

Flow Length Upstream to the Watershed Divide

Watershed Longest Flow-Path

Slope of Watershed Longest Flow Path

Watershed Lag-Time (SCS) t p :lag-time (min) L W :length of longest flow-path (ft) S :slope of the longest flow-path (%) CN :average Curve Number  t: analysis time step

Watershed Lag-Time (L/V) t p :watershed lag-time (min) L w :length of longest flow-path (ft) V w :longest flow-path average velocity (m/s)  t: analysis time step

Watershed Parameters

Hydrologic Parameters zWatershed yAbstractions and routing method yParameters zStream yRouting method yParameters

Routing Method

Pure-Lag Method zFlow is delayed a fixed amount of time t lag. t lag : flow time in the reach I: inflow to the reach Q: outflow from the reach

Muskingum Method zFlow is delayed a fixed amount of time K, and redistributed around its centroid. S: storage in the reach K: flow time in the reach (  t < K <  t/2X ) X: storage parameter I: inflow to the reach Q: outflow from the reach  t: analysis time step

Routing Method Flow time (L s /V s ) L s /V s <  t Muskingum Routing L s /V s >  t Pure Lag Routing L s :length of the stream V s :flow velocity in the stream  t: analysis time step

Hydrologic Parameters zWatershed yAbstractions and routing method yParameters zStream yRouting method yParameters

Pure Lag Parameters t lag :flow time in the reach (min) L s :reach length (m) V s :reach average velocity (m/s)

Muskingum Parameters K :flow time in the reach (hr) [Muskingum K] X :storage parameter [Muskingum X] L s :reach length (m) V s :reach average velocity (m/s) n :number of sub-reaches  t: analysis time step

Stream Parameters