Modeling and Mapping Soil Infiltration Rates in Dane County, WI

2010 ESRI Southeast Regional User Group Conference

Kathleen Arrington and Steve Ventura

“We have developed and evaluated a model of soil infiltration rates in Dane County, WI. The maps generated from this analysis can be used for local to regional scale land use planning, building on previous RGIS-supported technology transfer to local governments. The rates at which precipitation moves into soil and recharges groundwater aquifers is spatially variable, depending on several soil properties such as texture and structure. Land use activities also influence soil infiltration through a direct effect on surface land cover and long term effects on soil properties. In areas that depend on groundwater for potable water supplies or irrigation, planners and developers should be cognizant of potential impacts of land use changes on groundwater supplies. To do this, they need reliable models for predicting soil infiltration rates coupled with spatial extrapolations, for example, maps depicting critical groundwater recharge. An empirical model of soil infiltration rate (a pedotransfer function) was developed through detailed measurements at 50 sites throughout Dane County. A large-frame infiltrometer was used to establish steady-state infiltration rates. Soil properties, including texture, bulk density and organic matter were measured at each site, along with site conditions such as land use and topography. Regression based techniques were used to determine the best combination of soil and other properties to predict infiltration rates. This locally derived model was a substantial improvement over predictions based on soil properties alone and over general models. The best model of soil infiltration rate was used to predict rates at unsampled locations, based on texture (percent sand), bulk density, and land cover. Because the grain (spatial resolution) of land cover data is much finer than the soil survey (which is otherwise the sole basis for predicting infiltration), the spatial acuity of the ensuing maps was a substantial improvement.”