1. CRWR-PrePro Calculation of Hydrologic Parameters Francisco Olivera, Ph.D. Center for Research in Water Resources University of Texas at Austin Texas Department of Transportation (TxDOT) Water Resources Modeling Using GIS 2000 - Austin, Texas

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

3. Watershed Abstractions and Routing Method zAbstractions: rainfall/runoff transformation ySCS curve number method yInitial loss + constant rate loss zRouting: runoff/flow transformation ySoil Conservation Service (SCS) synthetic unit hydrograph

4. Watershed Abstractions Soil properties Precipitation (mm/hr) Runoff (mm/hr) Runoff = f(precipitation, soil properties, moisture conditions)

5. Watershed Routing Runoff (mm/hr) Flow (m 3 /s) Watershed

6. Watershed Routing Runoff (mm/hr) Flow (m 3 /s) Time Runoff and Flow Flow = f(Runoff, Watershed hydrologic properties) Time

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

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

9. Watershed Abstractions Average Curve Number SCS Method Initial + Constant Method Initial Loss (mm) Constant Loss (mm/hr)

10. Elevation Grid

11. Flow Length Downstream

12. Flow Length Upstream

13. Longest Flow-Path

14. Flow Length Downstream to the Watershed Outlet

15. Hydrologic Parameters zFlow length downstream to the sub-basin outlet.

16. Flow Length Upstream to the Watershed Divide

17. Hydrologic Parameters zFlow length upstream to the sub-basin divide.  A NODATA cell is defined at the sub-basin outlets before running the flow length function.

18. Watershed Longest Flow-Path

19. Hydrologic Parameters zSub-basin longest flow- path. zThe longest flow-path is the geometric locus of the points for which the sum of both flow lengths is a maximum.

20. Slope of Watershed Longest Flow Path

21. Hydrologic Parameters t p :sub-basin lag-time (min) L W :length of sub-basin longest flow-path (ft) CN :average Curve Number in sub-basin S :slope of the sub-basin longest flow-path (%)  t: analysis time step (min) zSub-basin lag-time according to the SCS formula:

22. Watershed Lag-Time (SCS) Flow length upstream and downstream Average Curve Number Length and slope of the longest flow-path Identification of the longest flow-path Lag-time

23. Hydrologic Parameters t p :sub-basin lag-time (min) L w :length of sub-basin longest flow-path (ft) V w :average velocity sub-basin longest flow-path (m/s)  t: analysis time step (min) zSub-basin lag-time according to 0.6 L/v formula:

24. Watershed Lag-Time (L/V) Flow length upstream and downstream Longest flow-path average velocity Length of the longest flow-path Lag-time

25. Hydrologic Parameters zSub-basin parameters: Grid code, area (Km 2 ), unit hydrograph model (SCS), length of longest flow path (m), slope of longest flow path (fraction), average curve number, lag-time (min), baseflow (none).

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

27. Routing Method

28. 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

29. 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

30. 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

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

32. Hydrologic Parameters t lag :reach lag-time (min) L s :length of reach (m) V s :reach average velocity (m/s) zReach lag-time for Pure Lag routing:

33. Hydrologic Parameters K :Muskingum parameter K (hr) X :Muskingum parameter X L s :reach length (m) V s :reach average velocity (m/s) n :number of sub-reaches zReach lag-time and number of sub-reaches for Muskingum routing:

34. Hydrologic Parameters  Pure lag routing for L s /60v s <  t, otherwise Muskingum routing. zReach parameters: Grid code, sub-basin code, length(m), velocity (m/s), routing method (Lag or Muskingum), lag time (min), Muskingum X, Muskingum K (hr), number of sub-reaches.