Integrating forests into water quality trading by identifying runoff and sediment yield reduction effect using swat modeling in East Texas

The hydrological model SWAT (Soil and Water Assessment Tool) was used to simulate runoff and sediment yield in the Alto Experimental Watersheds in Cherokee County, Texas, for the period from 2001 to 2003. SWAT-CUP (SWAT Calibration and Uncertainty Procedures) was adopted for calibration and uncertainty analysis. The adjusted streamflow and sediment yield models were assessed by RSR (root mean square error to the standard deviation ratio, 0.25 and 0.04), NSE (Nash-Sutcliffe efficiency, 0.94 and 1.00), and PBIAS (percent bias, -11.8 and -2.7). Hydrograph and flow duration curves also visually demonstrated goodness of fit of models by comparing simulated values with observations. Validation of streamflow model was performed based on 2004 field data.;Impact of land use change on streamflow and sediment yield was evaluated in the calibrated and validated SWAT models. When land use was altered from forests to low density residential, total runoff increased 73.1% from 230,924 m3 to 399,815 m3. Sediment yield elevated 75.8% from 102.4 ton to 180.0 ton.;The modeling approach provided a feasible approach to quantify and monetize water quality credits of forests. It enables WQT (Water Quality Trading) programs to include forests as potential sellers. Policy and conservation related issues were discussed from aspects of risk control, credits design, payment options, contract length, and pricing strategies.