ArcView Interface for SWAT2000
M. Di Luzio, R. Srinivasan, J.G. Arnold, S.L. Neitsch
AVSWAT-2000 (version 1.0) (Di Luzio et al., 2002) is an ArcView extension and a graphical user interface for the SWAT (Soil and Water Assessment Tool) model (Arnold et al., 1998). SWAT is a river basin, or watershed, scale model developed to predict the impact of land management practices on water, sediment, and agricultural chemical yields in large, complex watersheds with varying soils, land use, and management conditions over long periods of time. The model is physically based and computationally efficient, uses readily available inputs, and enables users to study long-term impacts. For a detailed description of SWAT, see Soil and Water Assessment Tool Theoretical Documentation and User's Manual, Version 2000 (Neitsch et al., 2001a; 2001b), published by the Agricultural Research Service and the Texas Agricultural Experiment Station, in Temple, Texas.
The SWAT model can be applied to support various watershed and water quality modeling studies. Examples of such studies include the following:
- National and regional scale water resource assessment considering both current and projected management conditions.
- Bosque River TMDL in Erath County, Texas. The project determined sediment, nitrogen, and phosphorus loadings to Lake Waco from various sources including dairy waste application areas, waste treatment plants, urban areas, conventional row crops, and rangeland. Numerous land management practices were simulated and analyzed (Saleh et al., 2000).
- Poteau River TMDL in Oklahoma/Arkansas. This project determined sediment, nitrogen, and phosphorus loadings in Wister Lake and dissolved oxygen, temperature, algae, and CBOD in the river. Management scenarios regarding poultry waste were analyzed (Srinivasan et al., 2000).
- DDT in the Yakima River basin, Washington. SWAT was used to simulate past and future sediment contamination by DDT in the Yakima River basin.
- The EPA office of pesticide registration is evaluating SWAT for use in landscape/watershed scale evaluation for pesticide registration.
- SWAT is being used extensively in the U.S. and Europe to assess the impact of global climate on water supply and quality (Rosenberg et al, 1999).
The AVSWAT-2000 ArcView extension evolved from AVSWAT, an ArcView extension developed for an earlier version of SWAT (Di Luzio et al., 1998). Important functional components and the analytical capability of ArcView GIS are implemented in several sets of customized and user friendly tools designed to: (1) generate specific parameters from user-specified GIS coverages; (2) create SWAT input data files; (3) establish agricultural management scenarios; (4) control and calibrate SWAT simulations; (5) extract and organize SWAT model output data for charting and display. The most relevant components of the system are: (1) a complete and advanced watershed delineator, (2) a tool for the definition of the Hydrologic Response Units, and (3) the latest version of the SWAT model with a relative interface. AVSWAT software is developed as an extension of ArcView GIS for the Personal Computer (PC) environment.
Within this system (Figure 1.1) ArcView provides both the GIS computation engine and a common Windows-based user interface. AVSWAT is organized in a sequence of several linked tools grouped in the following eight modules: (1) Watershed Delineation; (2) HRU Definition; (3) Definition of the Weather Stations; (4) AVSWAT Databases; (5) Input Parameterization, Editing and Scenario Management; (6) Model Execution; (7) Read and Map-Chart Results; (8) Calibration tool. Once AVSWAT is loaded, the modules get embedded into ArcView, and the tools are accessed through pull-down menus and other controls, which are introduced in various ArcView graphical user interfaces (or GUIs) and custom dialogs. The basic map inputs required for the AVSWAT include digital elevation, soil maps, land use/cover, hydrography (stream lines), and climate. In addition, the interface requires the designation of land use, soil, weather, groundwater, water use, management, soil chemistry, pond, and stream water quality data, as well as the simulation period, to ensure a successful simulation.
This tool is being applied worldwide and can support water quality analysis at the watershed level as well as at single stream segments, scales required for the support of most Total Maximum Daily Load (TMDL) programs.