This report was prepared by personnel of the Iowa district of the Water Resources Division of the U.S. Geological Survey under the supervision of S. W. Wiitala, District Chief, and Alfred Clebsch, Jr., Regional Hydrologist, Central Region. It was done in cooperation with the State of Iowa and with other agencies. This report is one of a series issued by Iowa. General direction for the series is by J. S. Cragwall, Jr., Chief Hydrologist, U.S. Geological Survey, and G. W. Whetstone, Assistant Chief Hydrologist for Scientific Publications and Data Management.