|Venterea, Rodney - Rod|
Submitted to: International Drainage Symposium
Publication Type: Proceedings
Publication Acceptance Date: 7/7/2004
Publication Date: 3/21/2004
Citation: Strock, J.S., Magner, J.A., Richardson, W.B., Sadowsky, M.J., Sands, G.R., Venterea, R.T. 2004. Variability of hydrologic regimes and morphology in constructed open-ditch channels. In: Cook, R.A., editor. Drainage VIII. Proceedings of the Eight International Drainage Symposium, March 21-24, 2004, St. Joseph, Michigan. p. 461-468. Interpretive Summary: In many areas within the U.S., engineered (tile) drainage of large areas of agricultural land is necessary to maintain production due to the prevalence of slowly permeable soils. Minnesota has more than 43,000 km of open drainage channels (ditches) that serve to collect and transport tile drainage water that in many cases is highly laden with nutrients, sediment, pathogens, and/or pesticides. The objective of this on-going study is to evaluate the assimilative capacity of open-ditches and identify open-ditch management strategies that would lead to reduced pollutant loadings to watersheds. The purpose of this paper is to compare the initial performance of two experimental open-ditch channels that have been constructed at the University of Minnesota Southwest Research and Outreach Center near Lamberton, MN. Water flow measurements indicated that the two paired open-ditch channels responded similarly to changes in water inflow, but that some variability in flow response between the two open-ditches was present. These flow differences were attributed to differences in the channel bottom elevation, and possibly to differences in seepage rates and vegetation density between the two ditches. These results point out the importance of making baseline comparisons between paired experimental systems prior to applying experimental manipulations, and will be used to improve the design of the current systems for future studies.
Technical Abstract: Open-ditch ecosystems are potential transporters of considerable loads of nutrients, sediment, pathogens and pesticides from direct inflow from agricultural land to small streams and larger rivers. Our objective was to compare hydrology and ditch channel morphology between two experimental open-ditch channels A open-ditch research facility incorporating a paired design was constructed during 2002 near Lamberton, MN. A 200-m reach of existing drainage channel was converted into a system of four parallel channels. The facility was equipped with water level control devices and instrumentation for flow monitoring and water sample collection on upstream and downstream ends of the system. Hydrographs from simulated flow during year one indicated that paired open-ditch channels responded similarly to changes in inflow. Variability in hydrologic response between open-ditches was attributed to differences in open-ditch channel bottom elevation and vegetation density. No chemical, biological, or atmospheric measurements were made during 2003. Potential future benefits of this research include improved biological diversity and integrity of open-ditch ecosystems, reduce flood peaks and increased flow during critical low-flow periods, improved and more efficient nitrogen cycling within the open-ditch ecosystem, decreased maintenance cost associated with reduced frequency of open-ditch maintenance.