Saylorville Lake provides storage to supplement the overflow of Lake Red Rock downstream, implementing flood control for the Des Moines River in Iowa and Mississippi Rivers. The drainage area is 18 km upstream of Des Moines. The reservoir has a basin area of 2230 ha that continues 39 km upstream from the drainage area. The reservoir has a basin area of 6500 ha at full storage capacity, that continues 87 km toward the highest part of the dam. The reservoir has reached full storage capacity during the year 1984, 1991 and 1993. Saylorville Lake watershed is estimated to be about 81% agricultural corn and soy field crop. Main concentrations of nitrate come from field crop. Nitrogen inputs are carried to the surface water in the watershed through
