The Lower Walnut Creek watershed (HUC 11030008) covers approximately 167 square miles in central Iowa. It is primarily an agricultural area with some urban and suburban development. The watershed is drained by Walnut Creek, a tributary of the Des Moines River. The hydrology of the watershed is influenced by its gently rolling topography and relatively impermeable soils. This results in frequent and sometimes severe flooding events. The area receives an average annual precipitation of 34 inches, with the majority falling as rain. The watershed does not have significant snowpack, as Iowa typically experiences mild winters with limited snowfall. Surface water in the area is primarily found in small streams and ponds, with some larger reservoirs for flood control and recreation. Reservoir constituents in the watershed include sediment, nutrients, and organic matter. These can contribute to water quality issues, especially during periods of high flow. Interesting climatic facts and trends in the watershed include an increase in the frequency and intensity of precipitation events, as well as an overall warming trend. These changes are expected to continue in the coming years, which may have significant impacts on the hydrology and ecology of the area.