Upper Bear River Watershed Analysis using Topmodel Project
Upper Bear River Watershed Analysis using Topmodel
Project Objective and Process u To model specific storm event using Topmodel in the Arc. GIS environment u Data collection u Terrain and Watershed Processing u Topmodel explanation u Results
Watershed Selection u u u Upper Bear River Uinta Mountain Range Relatively Undeveloped Data readily available Watershed with stream gage and precipitation data available
GIS Data Collection www. bearriverinfo. org u Climate u Environmental u Geology u Hydrology u Terrain u Watersheds u
Data Preparation DEM – 100 m X 100 m u NAD 83 – UTM Zone 12 N u
Terrain and Watershed Processing using Tau. DEM Only outputs used were: u demw – watersheds u demsca – dinf contributing area u demslp – dinf slopes u
Topmodel Introduction Conceptual model for runoff production u Developed for small upland catchments in the U. K. u After calibration Topmodel has been used in other humid temperate climates such as eastern U. S. u Successful models of mountain catchments in France and Spain after soil has “wetted up” u
Topmodel Procedure Assumption 1: Dynamics of saturated zone are approximated by steady state representations u Assumption 2: Hydraulic gradient of saturated zone is approximated by local surface topographic slope u Assumptions: u Ko=5 m/hr (hydraulic conductivity) u f=2 1/m (scaling parameter) u ne=0. 25 (effective porosity) u
Precipitation Event u Precipitation Event: P = 0. 5 inches from Sept. 19 – 21, 2004
Q u Qb = 44 cfs or 10800 m 3/day from USGS stream gage 0. 3 in 0. 2 in
mask demw – watersheds Mask – raster with values of 1 where demw was
λ Lambda demsca – dinf contributing area demslp – dinf slopes
Topmodel Calculations u Z’ is average depth to water table u. Z is depth to water table for each cell
Using Z Z<0 100% runoff u Z>P/ne 0% runoff u 0<Z<P/ne runoff=P-Z*ne u
Results u u u 284, 673 m 3 from Topmodel 173, 779 m 3 from USGS stream gage About 60% overestimation date time (days) flow (cfs) flowbase ft 3/day m 3/day 19 1 44 0 0 0 20 1 61 17 1468800 41609. 07 21 1 58 14 1209600 34266. 29 22 1 55 11 950400 26923. 51 23 1 52 8 691200 19580. 74 24 1 53 9 777600 22028. 33 25 1 50 6 518400 14685. 55 26 1 48 4 345600 9790. 368 27 1 46 2 172800 4895. 184 28 1 44 0 0 0 173779
Conclusions and reasons for error u More research is needed for Ko and ne assumptions u The watershed was not properly wetted up
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