Publications by William Simpkins

Journal Articles

Helmers, M.J., T.M. Isenhart, C.L. Kling, T.M. Moorman, W.W. Simpkins, and Mark Tomer. 2007.  Water quality in Agriculture 101: Heterogeneity of pollutants, practices, and programs. Choices (Paper).
 
Schilling, K.E., M. Tomer, P.E. Gassman, C.L. Kling, T.M. Isenhart, T.B. Moorman, W.W. Simpkins, C.F. Wolter. 2007. A tale of three watersheds: non-point source pollution and conservation practices across Iowa. Choices (Paper).

Simpkins, W.W. 2006. A multi-scale investigation of ground water flow at Clear Lake, Iowa. Ground Water 44 (1):35-46. (Paper)

Helmke, M.F., W.W. Simpkins, and R. Horton. 2005. Simulating conservative tracers in fractured till under realistic timescales. Ground Water 43 (6):877-889. (Paper))

Helmke, M.F., W.W. Simpkins, and R. Horton. 2005. Fracture-controlled transport of nitrate and atrazine in four Iowa till units. J. Environ. Qual. 34:227-236. (Paper)

Helmke, M.F., W.W. Simpkins, and R. Horton. 2004. Experimental determination of effective diffusion parameters in fractured till. Vadose Zone Journal 3:1050-1056. (Paper)

Burkart, M.R., W.W. Simpkins, A.J. Morrow, and J.M. Gannon. 2004. Occurrence of total dissolved phosphorus in surficial aquifers and aquitards in Iowa. J. Amer. Water Resources Assoc. 40(3):827-834. (Paper)

Simpkins, W.W., T.R.Wineland, R.J. Andress, D.A. Johnston, G.C. Caron, T.M. Isenhart, and R.C. Schultz. 2002. Hydrogeological constraints on riparian buffers for reduction of diffuse pollution: examples from the Bear Creek Watershed in Iowa, USA. Water Science and Technology 45 (9):61-68. (Paper)

Simpkins, W.W., M.R. Burkart, M.F.Helmke, T.N. Twedt, D.E. James, R.J. Jaquis, and K.J. Cole. 2002. Potential impact of earthen waste storage structures on water resources in Iowa. J. Amer. Water Resources Association 38(3):1-13. (Paper)

Rodvang, S.J. and W.W. Simpkins. 2001. Agricultural contaminants in Quaternary aquitards: a review of occurrence and fate in North America. Hydrogeology Journal 9(1):44-59. (Paper))

Eidem, J.M., W.W. Simpkins, and M.R. Burkart. 1999. Geology, groundwater flow, and water quality in the Walnut Creek watershed. lJ. Environ. Qual. 28:60-68.

Cambardella, C.A., T.B. Moorman, D.B. Jaynes, T.B. Parkin, W.W. Simpkins, and D.L. Karlen. 1999. Water quality in Walnut Creek watershed: Nitrate-nitrogen in soil, subsurface drainage water, and shallow groundwater. J. Environ. Qual. 28:35-44.

Burkart, M.R., W.W. Simpkins, M.F. Helmke, and P.J. Squillace. 1999. Infiltration of herbicides to an alluvial aquifer through tributary stream leakage. J. Environ. Qual. 28:69-74.

Squillace, P.J., M.R. Burkart, and W.W. Simpkins. 1997. Infiltration of agrichemicals from a tributary stream an alluvial aquifer. J. of the American Water Resources Association 33:89-95.

Simpkins, W.W. 1995. Isotopic composition of precipitation in central Iowa. J. of Hydrol. 172: 185-207.

Schultz, R.C., J.P. Colletti, W.W. Simpkins, C.W. Mize, and M.L. Thompson. 1995. Design and placement of a multi-species riparian buffer strip system. J. of Agroforestry Res. 29: 201-226.

Parkin, T.B. and W.W. Simpkins. 1995. Contemporary groundwater methane production from Pleistocene carbon. J. Environ. Qual. 24(2):367-372.

Simpkins, W.W. and T.B. Parkin. 1993. Hydrogeology and redox geochemistry of methane in a late Wisconsinan till and loess sequence in central Iowa. Water Resources Research 29(11): 3643-3657.

Simpkins, W.W. and K.R. Bradbury. 1992. Groundwater flow, velocity, and age in a thick, fine-grained till unit in southeastern Wisconsin. J. Hydrol. 132:283-319.

Dutton, A.R. and W.W. Simpkins. 1989. Isotopic evidence for paleohydrologic evolution of ground-water flow paths, southern Great Plains, United States. Geology 17:653-656.

Book Chapters

Schultz, R.C., T.M. Isenhart, W.W. Simpkins, J.P. Colletti, 2004. Riparian Forest Buffers in Agroecosytems – Structure, Function and Management – Lessons Learned from the Bear Creek Watershed Project in Central Iowa, USA. Chapter 2 in: P.K.R. Nair, M.R. Rao, and L.E. Buck, (eds). New Vistas in Agroforestry. Kluwer Academic Publishers, Dordrecht, The Netherlands. p. 35-50.

Schultz, R.C., J.P. Colletti, T.M. Isenhart, C.O. Marquez, W.W. Simpkins, and C.J. Ball. 2000. Riparian Forest Buffer Practices in H.E. Garrett, W.J. Rietveld, and R.F. Fisher, eds., North American Agroforestry: An Integrated Science and Practice. Madison, Wisconsin. American Society of Agronomy. p. 189-282.

Guidebooks
Dawson, J.P., M. Graesch, N.R. Iverson, W.W. Simpkins, and C.F. Vondra. 2005. ROCKIN' IN THE HEARTLAND: The Paleozoic/Quaternary Geology and Hydrogeology of Central Iowa. Guidebook for the 66th Annual Tri-State Geological Field Conference, Iowa State University, 85p. (Guidebook)

Simpkins, W.W. and M.R. Burkart, eds. 1996. Hydrogeology and water quality of the Walnut Creek watershed, Geological Survey Bureau, Guidebook Series no. 20, 105 pp.

Simpkins, W.W. 1993. Water, Water Everywhere...., Guidebook for the 57th Annual Tri-State Geological Field Conference and Geological Society of Iowa Field Trip Guidebook 58, Ames, IA, 139 pp.

Miscellaneous Publications

Simpkins, W.W. and M.F. Helmke. 2005. Stop 1A: Whatoff's borrow pit: fractures in till of the Des Moines Lobe. Guidebook for the 66th Annual Tri-State Geological Field Conference, Iowa State University. p. 12-19.

Simpkins, W.W. and E.G. Christianson. 2005. Stop 2: Ada Hayden Heritage Park: buried channels, quarry lakes, beaver dams, and the water supply of Ames, Iowa. Guidebook for the 66th Annual Tri-State Geological Field Conference, Iowa State University. p. 20-30.

Simpkins, W.W., T.R. Wineland, T.M. Isenhart, and R.C.Schultz. 2003. Hydrogeologic setting controls NO3-N removal in groundwater beneath multi-species riparian buffers. Proceedings of AWRA Spring Specialty Conference on Agricultural Hydrology and Water Quality, May 12-14, 2003, Kansas City.

Simpkins, W.W., 2003. An integrated field and modeling approach for understanding lake/groundwater interactions in Proceedings of Agriculture and the Environment: Research and Technology Update for Water and Air Quality, March 7, 2003, Scheman Building, Iowa State University, p. 13.

Simpkins, W.W. and M.R. Burkart. 2003. Hydrogeologic settings of earthen waste storage structures associated with animal feeding operations in Iowa. Proceedings of Conference on Application of Waste Remediation Technologies to Agricultural Contamination of Water Resources, July 30 to August 1, 2002, Kansas City.

Simpkins, W.W., T.R. Wineland, R.J. Andress, D.A. Johnston, G.C. Caron, T.M. Isenhart, and R.C. Schultz. 2001. Hydrogeological constraints on riparian buffers for reduction of diffuse pollution: examples from the Bear Creek Watershed in Iowa, USA. Fifth International Conference on Diffuse Pollution, Milwaukee, Wisconsin. June 20-15, 2001.

Simpkins, W.W. 2001. Hydrogeological and Geochemical Controls on Groundwater Quality in Iowa: What Really Happened to the Nitrate? Agriculture and the Environment: State and Federal Water Initiatives. Iowa State University, Seventh Annual Nonpoint Source Conference. March 5, 2001. p. 99-106.

Simpkins, W.W. 1999. Groundwater Quantity: A Water Quality Issue? Presented at the Conference “From the Heartland to the World: The Importance of Clean Water” sponsored by EPA Region 7, Seventh Annual Nonpoint Source Conference and the Iowa State University Provost’s Conference on Global Water Issues, March 24-26, 1999, Ames, Iowa, p. 23.

Isenhart, T.M., W.W. Simpkins, R.C. Schultz, J.P. Colletti, and J.W.Raich. 1998. Bear Creek watershed project. Guidebook for the 6th National Nonpoint Source Monitoring Workshop, “Interpreting Water Quality Responses to Land Treatment”, Sept. 21-24, Cedar Rapids, IA: 41-61.

Glanville, T.D., J.L. Baker, S.W. Melvin, T.L. Richard, W.W. Simpkins, M.R. Burkart, and J.L. Hatfield. 1998. Impacts of seepage from earthen waste storage structures in Proceedings of Animal Production Systems and the Environment: An International Conference on Odor, Water Quality, Nutrient Management, and Socioeconomic Issues, Iowa State University, v. 1 Oral Proceedings, 457-462.

Simpkins, W.W., T.B. Parkin, T.B. Moorman, and M.R. Burkart. 1995. Subsurface geology: a key to understanding water quality problems in Conference Proceedings, Clean Water - Clean Environment 21st Century, volume III, Practices, Systems, and Adoptions, March 5-8, Kansas City, Missouri, 251-254.

Schultz, R.C., J.P. Colletti, T.M. Isenhart, W.W. Simpkins, C.A. Rodrigues, P.A. Wray, M.L. Thompson, and J. Pease. 1995. Riparian buffer strip systems that improve water quality in Conference Proceedings, Clean Water - Clean Environment 21st Century, volume III, Practices, Systems, and Adoptions, March 5-8, Kansas City, Missouri, 235-238.

Schultz, R.C., J.P. Colletti, W.W. Simpkins, C.W. Mize, and M.L. Thompson. 1994. Design and placement of a multi-species riparian buffer strip system in R.C. Schultz and J.P. Colletti, eds., Proceedings of the Third North American Agroforestry Conference, August 15-18, 1993, Ames, Iowa, 109-119.