Calibration of a simple rainfall-runoff model for long-term hydrological impact evaluation

초록

The Long-Term Hydrological Impact Assessment (L-THIA) model is widely used to study direct runoff changes with respect to different land-use conditions. L-THIA was designed to assess the long-term impacts on the hydrology of a watershed for users who want to determine the relative change in runoff from one land-use condition to another. Some users, however, are interested in results that match observed stream-flow data, which includes both direct runoff and baseflow. A simple method of calibration of the L-THIA using linear regression of L- THIA predicted direct runoff and USGS-observed direct runoff values derived from hydrograph separation was developed and tested. The calibration model has been verified using three tests in the Little Eagle Creek watershed in Indiana. Results also raise additional questions regarding the factors that control runoff production and systematic under prediction of direct runoff by L-THIA compared to actual observed direct runoff data.