Upper Bear River Watershed Analysis using Topmodel

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 date time (days) flow (cfs) flow-base ft3/day m3/day 19 1 44 20 61 17 1468800 41609.07 21 58 14 1209600 34266.29 22 55 11 950400 26923.51 23 52 8 691200 19580.74 24 53 9 777600 22028.33 25 50 6 518400 14685.55 26 48 4 345600 9790.368 27 46 2 172800 4895.184 28 173779

Conclusions and reasons for error More research is needed for Ko and ne assumptions The watershed was not properly wetted up