TAPwaters: Technical Assistance Program for Watersheds

The TAPwaters project is dedicated to the application of hydrologic modeling to help answer management and research questions. Our current focus is toward use of the Soil and Water Assessment Tool (SWAT) in the St. Croix Basin and its subwatersheds.

Location and contact information:
St. Croix Watershed Research Station
16910 152nd St N
Marine on St. Croix, MN 55047

Jim Almendinger

(651) 433-5359 x19 (voice)

SWAT
The Soil and Water Assessment Tool (SWAT) is a watershed modeling program developed by the Agricultural Research Service of the U.S. Department of Agriculture. Its purpose is to predict yields of water, sediment, nutrients, and agricultural chemicals in large watersheds with diverse soils and land management practices. Learn More

"All models are wrong, but some are useful."
- George Box, paraphrased
Box, G.E.P., 1979. Robustness in the strategy of scientific model building. In: R.L. Launer and G.N. Wilkinson (Editors), Robustness in Statistics. Academic Press, New York.

SWAT Tips, Tricks, Trip-Ups, and Tools
Most things in SWAT work just fine. And, the manuals are full of important information and explain most of the theory and usage well. Yet in any large, fairly complex program there are a few quirks that are not apparent at first glance, and a few problems that appear to be outright bugs causing misleading results. Plus it can be useful to learn a few auxiliary tools to make your modeling more efficient. The following advice is the result of just a few years of modeling and is by no means comprehensive—mostly, these are things we wish someone had told us when we were getting started.

• Climate data processor - Those of you working in the USA know that the daily weather data available from the National Climatic Data Center (NCDC) are not in a format directly usable by SWAT. This downloadable packet has an Excel file with several VBA routines (macros) embedded to help process NCDC data into ArcSWAT format. Instructions and example data sets are included. Check the official SWAT webpage, also, because Srini and his students are developing a more comprehensive NCDC-data processor.
• Tools to consider learning - what other software and programming can help you use SWAT?
• Quirks in SWAT - a few observations about the less than obvious
• Suggested revisions to SWAT2000 - a fairly long list referring specifically to SWAT2000, noting some possible bugs and raising a few questions about some of the algorithms used. Many of these issues have been addressed and improved in SWAT2005, but not quite all. If SWAT is giving you some results that seem a little odd or wrong, you might scan this list to see if it's something we noticed, too. When we get more experience with SWAT2005, we'll try to update or replace this list of suggested revisions.

TAPwaters Reports

Almendinger, J.E. 2008. Modeled phosphorus exports from the Willow River watershed. St. Croix Watershed Research Station Fact Sheet, Science Museum of Minnesota, 4 pp. (Download PDF | 1.2 MB)

Almendinger, J.E., and Murphy, M.S. 2007. Constructing a SWAT model of the Willow River watershed, western Wisconsin. Report to Legislative Commission on Minnesota Resources, Wisconsin Department of Natural Resources, and National Park Service. St. Croix Watershed Research Station, Science Museum of Minnesota. (Download PDF | 2.5 MB)

Almendinger, J.E., and Murphy, M.S. 2007. Problems and solutions in applying SWAT in the Upper Midwest USA. Paper presented at the 4th International SWAT Conference, sponsored by the UNESCO-IHE Institute for Water Education, Delft, The Netherlands, 2-6 July 2007. 8 pp. (Download PDF | 452 KB)

Almendinger, J.E., and Murphy, M.S. 2005. Land-use change and agricultural practices in the Willow River watershed, western Wisconsin, 1992-2004. Interim report to Legislative Commission on Minnesota Resources and Wisconsin Department of Natural Resources. St. Croix Watershed Research Station, Science Museum of Minnesota, St. Paul, MN. 28 pp plus 13 pp of tables and figures. (Download PDF | 212 KB)

Funding and Cooperators

Funding to establish the TAPwaters project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative Commission on Minnesota Resources (LCMR). Continuation funding has been provided by the Wisconsin Department of Natural Resources and the National Park Service.