CONSERVATION EFFECTS ASSESSMENT FOR THE ST. JOSEPH RIVER WATERSHED
Location: National Soil Erosion Research Lab
Title: Developing an Understanding of the Complex Hydrology in the Upper Midwestern United States and Implications on Watershed Management and Planning
Submitted to: Role of Hydrology for Water Resources Management
Publication Type: Abstract Only
Publication Acceptance Date: April 11, 2008
Publication Date: October 13, 2008
Citation: Smith, D.R., Livingston, S.J., Larose, M., Heathman, G.C., Huang, C. 2008. Developing an Understanding of the Complex Hydrology in the Upper Midwestern United States and Implications on Watershed Management and Planning. In: Proceedings of the Role of Hydrology for Water Resources Management. Capri, Italy. pp. 32-33.
Isolated depressions, or “potholes” are a predominant landscape feature in much of the Midwestern United States. In most of this region, fields are systematically drained with sub-surface tiles conveying water to managed open ditches. It is a common practice in the region to install a pipe, called a “tile riser” in the isolated depressions to remove water as quickly as possible after a rainfall event. These systems have been greatly altered hydrologically, such that water in the open ditches arrives there from one of four sources: 1) direct surface runoff from adjacent fields; 2) drainage from sub-surface tiles; 3) drainage from adjacent fields; or 4) direct surface water inputs from tile risers located in the isolated depressions. Often times, there is very little direct contribution of surface runoff water to ditches from adjacent fields, because construction and maintenance of the ditches results in mounding of soil at the top of the ditch bank, thereby hydrologically separating the surface runoff of adjacent fields from the open ditches. In many instances, the isolated depressions that contribute surface runoff may be up to 1 km away from the open ditch. The management of the fields where the tile risers are located may have a greater impact on water quality in the open ditches and receiving streams following a storm event than the management of fields adjacent to the open ditches. Our objective is to identify the contribution of the sources of water to the open ditches, so that we may better understand how we should manage agricultural fields to minimize water quality impacts from agriculture on receiving streams. We use digital elevation models to locate isolated depressions in a 40,000 ha monitored watershed, and evaluate their contributions to the open ditches. This research will assist other researchers, land and resource managers and water quality modelers better understand the role hydrology plays in these landscapes.