Average annual precipitation within the study area ranges from 40 inches in the northern part of the basin to 48 inches in the south-central part of the basin and usually is distributed evenly throughout the year. Rainfall in the winter and early spring is generally of long duration, steady, and of mild intensity, whereas late spring and summer rainfall tends to be of short duration and high intensity. The White River Basin can be divided into six hydrogeomorphic regions that have similar natural characteristics on the basis of geologic, geomorphologic, and hydrologic factors. The till plain, glacial lowland, and fluvial deposits are the most intensively farmed regions in the White River Basin. The relatively impervious till limits infiltration and promotes surface runoff.
Tile drains are common in the till plain.
In general, soils in the glacial lowland are more permeable and better drained than soils in the till plain. Where such conditions exists, drainage ditches and tile drains are common. The bedrock uplands are unglaciated and are characterized by a hill and valley landscape with higher relief than other parts of the basin. Bedrock outcrops are common in this region and soils are generally thin. The karst plain is characterized by numerous sinkholes and solution features.