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A study modelling a storm event in ArcGIS, focusing on Upper Bear River watershed in Uinta Mountain Range. Data collection, terrain processing, Topmodel explanation, and results are detailed.
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Project Objective and Process • To model specific storm event using Topmodel in the ArcGIS environment • Data collection • Terrain and Watershed Processing • Topmodel explanation • Results
Watershed Selection • 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 • Climate • Environmental • Geology • Hydrology • Terrain • Watersheds
Data Preparation • DEM – 100 m X 100 m • NAD 83 – UTM Zone 12 N
Terrain and Watershed Processing using TauDEM • Only outputs used were: • demw – watersheds • demsca – dinf contributing area • demslp – dinf slopes
Topmodel Introduction • Conceptual model for runoff production • Developed for small upland catchments in the U.K. • After calibration Topmodel has been used in other humid temperate climates such as eastern U.S. • Successful models of mountain catchments in France and Spain after soil has “wetted up”
Topmodel Procedure • Assumption 1: Dynamics of saturated zone are approximated by steady state representations • Assumption 2: Hydraulic gradient of saturated zone is approximated by local surface topographic slope • Assumptions: • Ko=5 m/hr (hydraulic conductivity) • f=2 1/m (scaling parameter) • ne=0.25 (effective porosity)
Precipitation Event • Precipitation Event: P = 0.5 inches from Sept. 19 – 21, 2004
Q • Qb = 44 cfs or 10800 m3/day from USGS stream gage 0.2 in 0.3 in
mask demw – watersheds Mask – raster with values of 1 where demw was
λ Lambda demsca – dinf contributing area demslp – dinf slopes
Topmodel Calculations • Z’ is average depth to water table • Z is depth to water table for each cell
Using Z • Z<0 100% runoff • Z>P/ne 0% runoff • 0<Z<P/ne runoff=P-Z*ne
Results • 284,673 m3 from Topmodel • 173,779 m3 from USGS stream gage • About 60% overestimation
Conclusions and reasons for error • More research is needed for Ko and ne assumptions • The watershed was not properly wetted up