CHARACTERIZATION AND ANALYSIS OF AN ISOLATED WETLAND RECEIVING AGRICULTURAL RUNOFF

Agricultural runoff contains nutrients that can lead to eutrophication and other water quality problems when introduced to local waterways. In particular, drainage water from subsurface drains, frequently used in poorly drained agricultural soils in the Midwest, often contains nitrate-N concentrations exceeding the US EPA drinking water criterion. Wetlands are natural biofilters and have been shown to improve water quality. At Purdue's Agronomy Center for Research and Education (ACRE) in Tippecanoe County, Indiana, a small three acre wetland receives water from the tile drainage systems serving the nearby intensely managed agricultural fields. The water from the wetland flows into Indian Creek and eventually into the Wabash River. An initial hydrologic study is being conducted to determine the wetland's ability to improve the water quality.

The hydrology of the wetland is being determined by locating and monitoring the various water pathways with piezometers and stilling wells. Water samples are being collected from the two tile drain inlets, the piezometers, and the main outlet channel and analyzed for nitrogen and phosphorus. The presence of reducing conditions is also being monitored using Indicator of Reduction in Soil (IRIS) tubes in the soil of the main body of the wetland.

This study will provide information on the wetland's hydrologic response and patterns. The proportion of total inflow coming from the tile drains relative to other sources will be quantified. The nutrient load of the incoming and outgoing water will give an indication as to how well the wetland is improving the water quality.