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Element 4 - Calibrating the model

Calibration was achieved by adjusting the runoff coefficients and loading factors of primary land-use categories (see the table below) until the modeled flow rates and concentrations of E. coli in specific stream segments matched those in the records of the U.S. Geological Survey stream-gauging locations and E. coli database of the Interagency Task Force. The adjacent table summarizes the data used in the calibration process. In order to match the recorded data, the runoff coefficients had to be reduced by about 50 percent; however, the bacterial loadings were reduced by about 20 percent.

	Salt Creek Link 256	East Arm Little Calumet Link 249	Trail Creek Link 101
	Based on 2 years of data	Based on 4 years of data	Based on 5 years of data
Average summer base flow	1.3 m3/sec	1.4 m3/sec	2.4 m3/sec
Typical storm discharge	19.5 m3/sec	22.5 m3/sec	10.0 m3/sec
	Based on 2 years of data	Based on 2 years of data	Based on 2 years of data
Average E. coli base flow	180 CFU/100mL	220 CFU/100mL	270 CFU/100mL
Storm values of E. coli	1,700 CFU/100mL	21,000 CFU/100mL	15,000 CFU/100mL
Discharge values obtained from USGS gauging stations. E. coli values obtained from E. coli database of the Interagency Task Force. Storm values represent a 2-inch or greater rain.

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