Acknowledgments

Rodney R. Knight and Conner J. Haugh, USGS Hydrologists, assisted greatly with trend analysis. Philip S. Jen (formerly with the USGS) contributed valuable computing skills, which saved time and effort. Silvia E. Terziotti, USGS Information Technology Specialist, provided geographic information system (GIS) support and supervised the development of the crop and fertilizer datasets. David L. Lorenz, USGS Hydrologist, provided invaluable assistance with trend-analysis programs.