Temporal Analysis of Soil and Water Assessment Tool (SWAT) Performance based on Remotely Sensed Precipitation Products

Hydrological ProcessesHydrological Processes, Accepted for Publication

Kenneth J. Tobin and Marvin E. Bennett

“No study has systematically evaluated streamflow modeling between monthly and daily timescales. This study examines streamflow from seven watersheds across the United States where five different precipitation products were used as primary input into the Soil and Water Assessment Tool to generate simulated streamflow. Timescales examined include monthly, dekad (10 day), pentad (5 day), triad (3 day), and daily. The seven basins studied are the San Pedro (Arizona); Cimarron (north-central Oklahoma); mid-Nueces (south Texas); mid-Rio Grande (south Texas and northern Mexico), Yocano (northern Mississippi); Alapaha (south Georgia); and mid-St. Francis (eastern Arkansas). The precipitation products used to drive simulations include rain gauge, NWS Multisensor Precipitation Estimator, Tropical Rainfall Measurement Mission, Multi-Satellite (TRMM) Precipitation Analysis, TRMM 3B42-V6, and Climate Prediction Center Morphing Method (CMORPH). Understanding how streamflow varies at sub-monthly timescales is important because there are a host of hydrological applications such a flood forecast guidance and reservoir inflow forecasts that reside in a temporal domain between monthly and daily timescales. The major finding of this study is the quantification of a strong positive correlation between performance metrics and time step at which model performance deteriorates. Better performing simulations, with higher Nash-Sutcliffe values of 0.80 and above can support modeling at finer timescales to at least daily and perhaps beyond into the sub-daily realm. These findings are significant in that they clearly document the ability of SWAT to support modeling at sub-monthly time steps, which is beyond the capability for which SWAT was initially designed.”