Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-29
Total Federal Funds: $15,000 Total Non-Federal Funds: $30,020
Principal Investigators: Marty Frisbee, Indrajeet Chaubey
Abstract: Tile-drainage systems installed in agricultural watersheds in the Midwestern United States modify natural infiltration, percolation, and recharge processes and as a consequence, substantially change the distribution of groundwater flowpaths discharging to streams draining these watersheds. The concept of topography-driven flow (Tothian flow) has gained wide acceptance as a benchmark conceptual model for groundwater flow and groundwater/surface-water interactions in many different landscapes ranging from prairies with low topographic relief to mountainous watersheds with high topographic relief. Since groundwater is naturally recharged at topographic high points and discharged at topographic lows, groundwater flowpaths and flowpath lengths in a Tothian system will scale from local (short distance from recharge to discharge; short residence times), intermediate, and regional (long distance from recharge to discharge; long residence times). Thus, in a natural watershed, a distribution of local- to regional-scale groundwater flowpaths will be discharged to a stream. However, in agricultural watersheds of the Midwest, the water tables are commonly high and tile-drainage systems are installed to drain excess water quickly from the soil to enhance crop yields. These drainage systems route the excess water to a nearby ditch, stream, or river much quicker than natural drainage; thus, the streams flowing through these lands receive a substantial proportion of short-residence time water. Its believed that streamflow in these watersheds is largely, if not completely, composed of flow from tile-drainage systems. It remains unclear how tile-drainage affects intermediate- to regional-scale groundwater flowpaths and the discharge of these flowpaths to streams. This project will seek to address this knowledge gap by conducting synoptic sampling along the main channel of the Wabash River and its major tributaries to identify the presence of and quantify the magnitude of groundwater discharge to streams. Water samples will be analyzed for general chemistry, radon-222 (222Rn), and tritium (or other) to identify groundwater components.