Mapping infiltration rates in Dane County, Wisconsin.

摘要

Dane County, Wisconsin has experienced rapid population growth and development over the last 40 years. Groundwater pumping and loss of recharge associated with development have contributed to significant groundwater drawdown---up to 20m compared to predevelopment conditions. Infiltrating stormwater is a practice that may minimize recharge loss in developed areas, especially if the stormwater is directed to high-infiltration soils. The saturated hydraulic conductivity (Ksat), which is a measure of how easily a soil transmits water, can be used to compare the infiltration potential of different soils. Most Ksat estimates are based on measurements in which water flow is primarily through micropores, rather than macropores. However, macropore flow can dominate the infiltration rate when the soil is saturated, as it is likely to be in areas receiving stormwater runoff.;The objective of this study was to produce a relative infiltration map for Dane. County that is based on local infiltration measurements that do include macropore flow. Infiltration measurements were taken (50 sites, 124 measurements) and soil samples collected for a wide variety of soils and land uses across Dane County. Multiple regression analysis was done to examine relationships between Ksat and soil and non-soil properties (landcover and topography). Percent sand and bulk density of the surface horizon were the two best soil property predictors of Ksat. Landcover was the best non-soil Ksat predictor. These relationships were used to develop a relative infiltration map for Dane County from existing geospatial data layers for soils, landcover and topography. Including landcover as a predictor of Ksat improves the accuracy of the regression model compared to the model based on soil properties alone (percent sand and bulk density) and also increases the spatial resolution of the relative infiltration map. This map is designed for use in township or watershed-scale land use planning. Local land use planners can use this information to identify the suitability of potential development areas for infiltration-based stormwater management.