Simulating Hydrologic Response From Arizona Ponderosa Pine Watersheds Using the Basins-Swat Modeling System.

Abstract

"Better Assessment Science Integrating Point and Nonpoint Sources (BASINS)" (U.S. EPA, 2001) is a multi-purpose environmental analysis system that can facilitate development of Total Maximum Daily Loads (TMDLs) and water quality criteria. Soil and Water Assessment Tool (SWAT) underlain BASINS, is a continuous hydrologic model designed for a simulation for a large, environmentally complex watershed. In this study, BASINS-SWAT was applied to small and medium sized ponderosa pine watersheds in north-central Arizona where typical semi-arid climatic characteristics are observed including high variability in annual precipitation. Purposes of this study were to provide information on parameter selection, estimation, sensitivity, and optimization useful for model calibration process for this type of watershed. Despite the disadvantageous characteristics of the study watersheds, BASINS-SWAT simulated streamflow fairly well on an annual basis. CN2 was the largest contributing parameter to the model calibration, followed by ESCO and SMFMN. The small watershed showing the lower model efficiency was more sensitive to the climatic and vegetative impacts than the medium sized watershed. Due to the homogeneous characteristics of the study watersheds, discrtetization of the watershed varied only topographic parameters of each sub-watershed, which resulted in very little influence on the output of the model.