Hydrologic modeling to evaluate E. coli loading in the Dunes Creek Watershed, Porter County, Indiana

Status Start Date End Date Locations
completed Feb 14, 2005 Aug 13, 2005 Porter
Director: Sally Letsinger
Other Researchers: Sally L. Letsinger
Funding: Save the Dunes Conservation Fund
Issue: The Indiana Department of Environmental Management's Impaired Waters List for 2002 and 2004 identify Dunes Creek as impaired for biotic communities and E. coli. The water-quality problems in Dunes Creek have been attributed to the ditching and the consequential loss of wetlands. This alteration of the channel network and the effects of commercial and residential development, as well as agriculture, have significantly altered the hydrology and water quality of the creek.
Objective: The primary issues in the Dunes Creek Watershed are sources of E. coli. We conducted surface-water numerical modeling to:
1) Represent the hydrology, sediment, and bacterial characteristics in the drainage network; and
2) Simulate how land-use and land-management changes (for example, adding riparian buffers, filling or plugging ditches) might achieve reduction of  E. coli in Dunes Creek.
Approach: For this investigation, the primary constituents were water, sediment, bacteria, nitrate, nitrite, ammonium, and phosphate. The model was evaluated as a whole, by reach, and spatially during both base-flow and storm-flow conditions. The largest potential source of bacteria to the watershed is unknown, but is theorized to be a combination of waste deposited in ditches by wildlife, and E. coli attached to stream-bed sediments that are redistributed during storms. Much of the modeling work was focused on the realistic representation of the conditions in the watershed, particularly the distribution of soils and land use across the watershed.
Products: The results of the study were mapped in GIS format, and the results of the modeling exercise show that during storm flow, most water-quality constituents evaluated could be improved by filling ditches and/or restoring wetlands.
Benefits: This results of this study led to the recommendation to restore vegetated riparian buffers (strips of vegetated land along the edges of creeks and rivers) and wetlands to reduce E. coli in Dunes Creek.