Watershed Studies


Nonpoint source pollution from nitrate-nitrogen (nitrate) and phosphorus (P) is a major societal challenge in Iowa, contributing to nutrient enrichment in local streams and lakes and development of hypoxic (dead) zones in regional water bodies, including the Gulf of Mexico. IGS researchers and collaborators use watershed analyses and models to investigate watershed processes and patterns and develop solutions for our water quantity and quality challenges.


IGS researchers, led by Dr. Keith Schilling and Matthew Streeter, examined nutrient loading patterns to groundwater near West Lake Okoboji and in Clear Creek watershed. In these studies, IGS developed the concept of “groundwater response units” to quantify groundwater loading patterns at a regional scale.



Other watershed studies have incorporated the use of models such as the Soil Water Assessment Tool (SWAT) to quantify nonpoint source impacts at a watershed scale and analyze remedial scenarios.  In one example, nitrate loading patterns were analyzed for the Des Moines River basin using SWAT:



Some examples of the type of modeling studies conducted by IGS staff and collaborators include the following:


Schilling, K.E., M.K. Jha, Y.K. Zhang, P.W. Gassman, and C.F. Wolter.  2008.  Impact of land use and land cover change on the water balance of a large agricultural watershed: historical effects and future directions.  Water Resources Research 44,W00A09, doi:10.1029/2007WR006644. 

Schilling, K.E., P. Gassman, C. Kling, T. Campbell, M. Jha and C. Wolter. The potential for agricultural land use change to reduce flood risk in the large Midwestern watershed, U.S.A. 2013. Hydrological Processes. DOI:1002/hyp.9865.

Drake, C.W., C.S. Jones, K.E. Schilling, A. Arenas Amado, and L.J. Weber. 2018. Estimating nitrate-nitrogen retention in a large constructed wetland using high-frequency, continuous monitoring and hydrologic modeling. Ecological Engineering 117:69-83.

McLellan, E., D. Robertson, K. Schilling, M. Tomer, J. Kostel, D. Smith and K. King. 2015. Reducing nitrogen export from the Corn Belt to the Gulf of Mexico: agricultural strategies for remediating hypoxia.  Journal of the American Water Resources Association, 51:263-289.

Jha, M.K., C.F. Wolter, K.E. Schilling, and P.W. Gassman. 2010. Assessment of TMDL implementation strategies for the Raccoon River, Iowa.  Journal of Environmental Quality doi:10.2134/jeq2009.0392. 


IGS staff welcomes research ideas and collaboration on these topics and other watershed questions and issues that impact Iowans.