Significance of Exchanging SSURGO and STATSGO Data When Modeling Hydrology in Diverse Physiographic Terranes

The Water Availability Tool for Environmental Resources (WATER) is a TOPMODEL‐based hydrologic model that depends on spatially accurate soils data to function in diverse terranes. In Kentucky, this includes mountainous regions, karstic plateau, and alluvial plains. Soils data are critical because they quantify the space to store water, as well as how water moves through the soil to the stream during storm events. We compared how the model performs using two different sources of soils data—Soil Survey Geographic Database (SSURGO) and State Soil Geographic Database laboratory data (STATSGO)—for 21 basins ranging in size from 17 to 1564 km2. Model results were consistently better when SSURGO data were used, likely due to the higher field capacity, porosity, and available‐water holding capacity, which cause the model to store more soil‐water in the landscape and improve streamflow estimates for both low‐ and high‐flow conditions. In addition, there were significant differences in the conductivity multiplier and scaling parameter values that describe how water moves vertically and laterally, respectively, as quantified by TOPMODEL. We also evaluated whether partitioning areas that drain to streams via sinkholes in karstic basins as separate hydrologic modeling units (HMUs) improved model performance. There were significant differences between HMUs in properties that control soil‐water storage in the model, although the effect of partitioning these HMUs on streamflow simulation was inconclusive.