The goal of this project is to characterize the effects of preferential flow paths in sludge-amended soils. Field work involves the monitoring of drain flow to obtain data to test the equivalence of infiltration rate, permeability, and effluent water quality from sludge-amended and non-amended plots. Laboratory analysis involves the evaluation of temporal variations in permeability from soil cores subjected to water in which the variation in water quality covers the range of the ionic strength of divalent cations measured in leachate from municipal sludge.

Graduate student Ashok Verma digitizes a soil map to create a GIS data layer to be used in delineating subsurface drainage systems.

Most flood flow models do not have the capability of including subsurface drain flow. Drain flow models, on the other hand, are mainly field-scale models that are virtually impossible to apply at a watershed scale. This project addresses the development of a composite model in which a subsurface drainage model is subsumed into a flood flow model. The amalgamation of these two components will potentially result in better prediction of flood peaks and of flood water quality.

Simulated rainfall was applied to several tillage systems on two soil types at slopes ranging from 1.6% to 10%. Soil surface geometry was recorded using a pin-type rillmeter. In the Catlin soil, rills appeared to widen as erosion progressed. In the Tama soil, rills appeared to become deeper with reduced width per unit of cross-sectional flow area as erosion progressed. The equation of Elliot (1988) appeared to be a better predictor of mean rill widths. For tillage systems with crop residue cover ranging from 15% to 54% in the Tama soil, both equations tended to underestimate rill.

During the first five years of the Little Vermilion River Nonpoint Source Hydrologic Unit Area Project, researchers have monitored nitrate concentration and flow in the tile drainage systems on eight sites.

Optimal nitrogen management practices for the seven cropped fields will be determined and applied. The specific practices that are optimal and practical for a particular farm will vary depending upon soils and the farmer's time constraints at different times of the year. We anticipate that the nitrogen management plans, once adopted, will produce more profit for the farmers and, thus, the farmers will continue to use the recommended practices long after the financial remuneration is available.

Drinking water supplies in East-Central Illinois are subject to nitrate contamination because field tile systems provide direct flow paths between leached nitrate and surface drainage systems. The purpose of this study was to develop a model for predicting surface flow and nitrate loading at the outlet of a tile-drained watershed in Champaign County, Illinois. The GRASS GIS was used to explore relationships between watershed characteristics and watershed outlet response. A linear model, relating field tile flow and watershed soils to outlet flow, was particularly successful in predicting 1993 measurements.