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.

• SWAT2009 modified code - We've identified some problems with the way SWAT deals with water infiltrating from Ponds, Wetlands, and Reservoirs. Surface outflow from Ponds was a bit of a problem as well. Starting with SWAT2009 rev. 486, we fixed the code ourselves and make it available here, as a beta version for you to try out. Please note that this is NOT an official version. We will work with the SWAT development team in Texas to see if they will incorporate our code revisions into their official release version. The download package here includes the swat2009 executable, the entire source code, and a read-me file that explains the logic of the code changes.
  
  (Note that previously we'd attempted the same modifications to the SWAT2005 code. But in revising the SWAT2009 code we found some bugs in our earlier efforts - so if you're using our old SWAT2005 code, you really should upgrade to SWAT2009.)
  
  
• Climate data - Probably the best place to obtain climate data for running SWAT models for USA watersheds is from the ARS, at their US Climatic Data site, which yields SWAT-ready data files. Another source would be the Utah State Climate Center, which has data in nearly SWAT-ready format. Otherwise, if you get your data from the National Climatic Data Center (NCDC), the data will not be in a format directly usable by SWAT. Hence we wrote an NCDC Climate data processor, which is an Excel file with several VBA routines (macros) embedded to help hammer the data into a format for use in SWAT. This downloadable packet includes instructions and example data sets.
• Tools to consider learning - what other software and programming can help you use SWAT?

TAPwaters Reports

Murphy, M.S., 2010. Application of the Soil and Water Assessment Tool (SWAT) to the Willow River Watershed, St. Croix County, Wisconsin. M.S. Thesis, University of Minnesota, Minneapolis, MN, 128 pp. (Download PDF | 1.9 MB)

Almendinger, J.E., and Ulrich, J.S. 2010. Constructing a SWAT model of the Sunrise River watershed, eastern Minnesota. Report to the National Park Service and Minnesota Pollution Control Agency. St. Croix Watershed Research Station, Science Museum of Minnesota, 63 pp. (Download PDF | 8 MB)

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.