Improvement and Application of the ArcGIS-based Model to Estimate Direct Runoff

초록

The Long-Term Hydrologic Impact Assessment (L-THIA) model is a quick and straightforward analysis tool to estimate direct runoff and nonpointsource pollution. L-THIA was originally implemented as a spreadsheet application. GIS-based versions of L-THIA have been developed in ArcView3 and upgraded to ArcGIS 9. However, a major upgrade was required for L-THIA to operate in the current version of ArcGIS and to provide moreoptions in runoff and NPS estimation. An updated L-THIA interfaced with ArcGIS 10.0 and 10.1 has been developed in the study as an ArcGISDesktop Tool. The model provides a user-friendly interface, easy access to the model parameters, and an automated watershed delineation process. Themodel allows use of precipitation data from multiple gauge locations for the watershed when a watershed is large enough to have more than oneprecipitation gauge station. The model estimated annual direct runoff well for our study area compared to separated direct runoff in the calibration andvalidation periods of ten and nine years. The ArcL-THIA, with a user-friendly interface and enhanced functions, is expected to be a decision supportmodel requiring less effort for GIS processes or to be a useful educational hydrology model.

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