Construction of a Precipitation-Runoff Model for Pheasant Branch Creek, Middleton, WI
by Jeffrey J. Steuer
USGS, Water Resources Division
8505 Research Way
Middleton, WI 53562-3586
Internet: jjsteuer@usgs.gov
Phone: (608) 821-3830
FAX: (608) 821-3817
Editor's note:
This modeling work will be presented at a joint meeting of the Wisconsin Section of the American Water Resources Association (AWRA) and the Midwest Regional Chapter of the Society of Environmental Toxicology and Chemistry (SETAC), held March 25-26, 1999 in La Crosse, Wisconsin.
Abstract
The precipitation runoff modeling system (PRMS) (Leavesley and others, 1983) is being used to model the hydrologic response of the Pheasant Branch watershed. A significant portion of the 18.3 square mile basin, the North Fork sub-basin (9.6 sq. mi.), is primarily used agriculturally but is expected to undergo significant urbanization in the future. This model will be used to quantify flood peak and groundwater recharge differences resulting from a fully urbanized condition, both with and without management or runoff controls. The model will also assist in locating potential sites for runoff controls and to evaluate infiltration and land-use practices to ensure future flood peaks do not exceed the present condition flood peaks. In addition, the surface water model will provide spatially variable infiltration rates on a monthly time scale to assist development of a corresponding groundwater model.The 11,700 acre basin is represented by flow planes (approximately 250 acres per plane) that vary in properties such as imperviousness, infiltration (Green-Ampt parameters), slope, aspect, and precipitation. To reduce calibration uncertainty, 36 double-ring infiltrometer tests were conducted to establish the infiltration curves for various land-use and soil types.
Precipitation from six gage sites and temperature from one site provide forcing function data for the model. Continuous discharge records at three gaging stations will be used for model validation. Limited discharge data, collected at three sub-basin (500 to 1200 acres) outlets, will be used to confirm flow plane infiltration curves.
Average annual precipitation, for the calibration interval of 1993 to 1996, was 35.3 inches. The model simulated, on average, that 4.4 inches were intercepted, 21.3 inches were lost to evapotranspiration, 4.1 inches were infiltrated to the regional groundwater system, and 5.5 inches contributed to the Pheasant Branch streamflow.
To assess storm events, 24 storms were simulated on 5-minute intervals and compared to the discharge sites. The largest runoff event during the calibration interval occurred in July 1993 (746 ft3/s; recurrence interval ~25 years). The model simulated storm volume, peak timing and peak magnitude well at the overall basin outlet without modification to storm calibration parameters. The internal sub-basins have yet to be assessed.
The model will also be used to simulate sediment and phosphorus loads from the urbanized South Fork basin and the agricultural North Fork basin. Preliminary data indicate total suspended solids median concentrations from the South Fork are twice as high as from the North Fork (50 mg/L and 25 mg/L respectively). North Fork total phosphorus concentrations are about 5 times greater than the South Fork (1.5 mg/L and 0.3 mg/L respectively).
Reference
Leavesley, G.H., Lichty, R.W., Troutman, B.M., and Saindon, L.G., 1983, Precipitation-runoff modeling system: user's manual: U.S. Geological Survey Water-Resources Investigations Report 83-4238, 207 p.Stewart Rounds, SMIG coordinator <sarounds@usgs.gov>
U.S. Geological Survey
http://smig.usgs.gov/SMIG/features_0399/pheasant.html
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