Aerial Infrared Mapping of Subsurface Drainage Systems
R. A. Cooke,* M. C. Hirschi, J. D. Davis
Illinois C-FAR

The primary objective of this project is to provide researchers, farmers, farm managers, policy makers, farm organizations, and agribusiness interests in Illinois with maps that show the layout of subsurface drainage (tile) systems in the Lake Decatur watershed, one of the most heavily tiled watersheds in the state. Drain (tile) mapping is possible because the soil over efficiently draining tile lines dries faster than the soil at other locations in the field and has higher reflectance in the infrared region of the radiation spectrum.

The Effect of Water Table Management on Productivity and Water Quality
R. A. Cooke,* J. K. Mitchell
University of Illinois; U.S. Department of Agriculture

The primary objective of this project is to optimize the performance of subsurface drainage systems. Procedures are being developed to map existing drainage systems and to estimate the effective regions of influence of random drainage systems or monotiles.

Modeling Flood Flows in Flat, Tile-drained Watersheds
R. A. Cooke*
Illinois Groundwater Consortium

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 virtuallyimpossible 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.

Management Practice Effects on Nitrate-N Concentrations in the LVR
J. K. Mitchell,* M. C. Hirschi, G. F. McIsaac
Illinois Council for Food and Agriculture Research; University of Illinois

Nitrates in subsurface tile flow have been monitored for six years from fields with various tillage and cropping management practices. The effect of the application of large amounts of nitrogen fertilizer, particularly as a preplant operation, was shown in the nitrate-N concentrations from the drains. The preplant anhydrous-N application systems with average nitrogen application of 110 kg/ha/yr had a mean concentration of nitrate-N of 9.4 mg/L. The mean concentration of nitrate-N from a permanent meadow field was 1.0 mg/L. Water table control systems have been installed on four drain systems to evaluate the potential for enhanced denitrification.

Modeling Agricultural Practices for Water Quality Improvement Using GIS
J. K. Mitchell,* M. C. Hirschi, G. F. McIsaac, S. E. Walker
University of Illinois; U.S. Department of Agriculture

Rainfall-runoff simulation models were applied to an agricultural watershed containing tile drains. Individual model components were examined to determine their applicability for tile-drained fields. Specifically, the SCS curve number method was modified to represent the rainfall-runoff process as affected by subsurface drainage.