The stream runoff model developed by Mohseni and Stefan (1996) has a monthly
time scale and is based on the water budget theory. Its function is to make mean monthly
runoff projections under different climate scenarios. The model uses 6 climate variables,
11 watershed and soil parameters, and 3 parameters related to both climate and runoff.
Some of the parameters are measurable and, therefore, obtainable as model input. The
model lumps all watershed and soil parameters both vertically and horizontally. A nonsystematic
calibration procedure gives different results, depending on the initial values
chosen for some of the calibration parameters. The calibration parameters of the model
are related to the two processes which are the most difficult to quantity and where the
most information is required: direct runoff and snowmelt runoff. A systematic calibration
procedure has been added to the original model to avoid inconsistencies in the results.
The systematic calibration procedure is selected for the direct runoff parameters. For the
snowmelt runoff, only some modifications in input are implemented. Base flow algorithm
also required some changes in estimating the hydraulic conductivity of the storage below
the root zone in order to better fit the water budget theory and Darcy's Law.
For testing, the modified model is applied to two watersheds in two different
climate regions, one in northern Minnesota and one in southwestern Oklahoma.
National Agricultural Water Quality Laboratory, US Department of Agriculture; US Environmental Protection Agency
Mohseni, Omid; Stefan, Heinz G..
Calibration of the Monthly Time Scale Runoff Model.
St. Anthony Falls Laboratory.
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