A MONTHLY STREAMFLOW MODEL

To estimate the potential consequences of projected global warming on streamflow, a deterministic model for a monthly timescale has been dev eloped. The model structure is based on the water budget theory and co ntains deterministic relationships to estimate four components of stre amflow: direct runoff, interflow, base flow, and snowmelt. The model i nputs are six climate variables for each time step and 10 watershed pa rameters. The model has four calibration parameters which are related to direct runoff and snowmelt runoff. The model has been applied to th e Little Washita River watershed in Oklahoma and the Baptism River wat ershed in Minnesota. The former is an agricultural watershed with a wa rm and seasonally dry climate, and the latter is a forested watershed with a cool and humid climate. The model simulates mean monthly stream flow in the Baptism River with a Nash-Sutcliffe coefficient (NSC) of 0 .99 and a correlation coefficient of 0.83. For the Little Washita Rive r the same simulation measures are 0.94 and 0.89, respectively.