1. Upper Bear River Watershed Analysis using Topmodel

2. Project Objective and Process
To model specific storm event using Topmodel in the ArcGIS environment
Data collection
Terrain and Watershed Processing
Topmodel explanation
Results

3. Watershed Selection Upper Bear River Uinta Mountain Range
Relatively Undeveloped
Data readily available
Watershed with stream gage and precipitation data available

4. GIS Data Collection www.bearriverinfo.org Climate Environmental
Geology
Hydrology
Terrain
Watersheds

5. Data Preparation
DEM – 100 m X 100 m
NAD 83 – UTM Zone 12 N

6. Terrain and Watershed Processing using TauDEM
Only outputs used were:
demw – watersheds
demsca – dinf contributing area
demslp – dinf slopes

7. 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”

8. 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)

9. Precipitation Event
Precipitation Event: P = 0.5 inches from Sept. 19 – 21, 2004

10. Q
Qb = 44 cfs or m3/day from USGS stream gage
0.2 in
0.3 in

11. mask
demw – watersheds
Mask – raster with values of 1 where demw was

12. λ Lambda
demsca – dinf contributing area
demslp – dinf slopes

13. Topmodel Calculations
Z’ is average depth to water table
Z is depth to water table for each cell

14. Using Z Z<0 100% runoff Z>P/ne 0% runoff
0<Z<P/ne runoff=P-Z*ne

15. 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 21 58 14 22 55 11
950400 23 52 8
691200 24 53 9
777600 25 50 6
518400 26 48 4
345600 27 46 2
172800 28
173779

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