The data used for the L-THIA analysis of the LEC watershed include land use based on remote sensing analysis for 1973, 1984, and 1991 (Grove 1997), Soil Survey Geographic (SSURGO) soil data developed by the U.
Once the initial data preparation was completed, a modified version of the Web-based L-THIA model was used to compute daily direct runoff values for the period 1973 to 1991.
This study presents the development and testing of a simple calibration approach based on observed direct runoff values derived from readily available stream-gauge data available over the Internet; no complicated processing is required in the calibration process and, other than the stream-gauge data, no additional information is required beyond that used in an L-THIA model run.
L-THIA model predictions are found to be approximately 50 percent lower than actual observed direct runoff for the LEC watershed.
If the pace of land-use change or intensification is not captured in the available data, then L-THIA results should underpredict observations during periods of urbanization.