1. Rick Cruse, Matt Helmers, Greg Brenneman, and John Laflen Iowa Water Center, and Iowa State University Extension

4. Runoff Occurs When Rainfall Intensity exceeds rate (infiltration rate) that water can enter the soil (sponge). Infiltration rate affected by Physical characteristics of the soil-soil texture and soil structure Soil moisture Cover on the soil and management of the soil Rainfall intensity

5. 140 years of Iowa Land Use

6. Mean Annual Base Flow, Surface Runoff, And Total Water Yield, Treynor IA 1964-71

7. Cedar River Annual Flow Cedar Rapids

8. Cedar River Peak Flow Rates

9. Concluding Comments Loss of Permanent Grass Cover Has Increased Water Yield- Annual Plants (Corn and Soybeans) Transpire Less Water Than Annual Plants (Grass). For Extreme Floods-(>100 yr Return Period) Minimal Impact of Last 75 yrs of Land Use Changes Major Impact of Plowing the Prairies and of Man Made Drainage Ditches