Daily estimates of rainfall, water runoff, and soil erosion in Iowa

ABSTRACT:

The major water quality impairment in the Midwest United States is sediment eroded from agricultural lands. Yet, few understand where or when erosion occurs, or the dynamics of soil erosion, the relative impact of precipitation, topography, land management and severe events over time and space. The objectives of this project are to: 1) develop methodology for estimating near real time spatial and temporal soil erosion and water runoff losses; and 2) explore issues in applying the method to a large area by setting up and running a prototype system for the state of Iowa. To accomplish this, soil erosion and water runoff loss are estimated daily at the township level (∼10 by ∼10 km area) (∼6.2 mi)² and a map is posted on the Internet daily showing precipitation with runoff and soil erosion estimates for every Iowa township. We use Water Erosion Prediction Project (WEPP), a daily simulation model, to compute soil erosion and surface runoff. WEPP uses accumulated precipitation by 15-minute periods obtained with NEXRAD radar. Other needed weather data are obtained from an Iowa weather network. The National Resources Inventory provides soil, topography, cropping and management information required for running WEPP. Daily and annual spatial precipitation, runoff and erosion estimates illustrate a high level of spatial variability related to topography, precipitation characteristics, soils and management practices.