Comparison of Four Models (STEPL, PLOAD, L-THIA, and SWAT) in Simulating Sediment, Nitrogen, and Phosphorus Loads and Pollutant Source Areas

摘要

This study compared the utility and results of four watershed models that include water quality elements: Spreadsheet Tool for Estimating Pollutant Load (STEPL), a GIS-based model to calculate pollutant loads for watersheds (PLOAD), Long-Term Hydrologic Impact Assessment (L-THIA), and ArcGIS Soil and Water Assessment Tool (ArcSWAT). These models are different in their levels of complexity, data requirements, time step, and simulation techniques. Therefore, different scenarios were conducted to test some of the standard applications of each model based on data quality and model capabilities. Climatological, land use, and soil datasets as well as flow rates, sediment, nitrate, and total P concentrations were collected for the Pomona Lake watershed inKansas over 30 years. Stakeholders' information was integrated into the models to the extent possible. Using results obtained from STEPL, L-THIA, PLOAD, and uncalibrated ArcSWAT for estimating long-term (30 years) average pollution loads in a watershed can result in incorrect load estimation. In addition, the STEPL, L-THIA, and PLOAD models may not be the most reliable in identifying pollutant source areas in a watershed. Therefore, in the context of effective resource allocation, use of simple models (such as STEPL, L-THIA, and PLOAD) is not suggested for critical source area targeting for watershed planning if the nature of the problem is complex. However, the simple models can still be used to evaluate relative contribution of different land uses tooverall pollution loads.