DESIGN AND TESTING OF A PAIRED DRAINAGE CHANNEL RESEARCH FACILITY

Abstract

In watersheds where artificial drainage is practiced, surface and subsurface runoff from agricultural lands is oftencarried by a network of open ditches that function as headwater streams. Open-channel ecosystems receive direct surfaceand subsurface inflow from agricultural land and act as potential conduits of considerable loads of nutrients, sediment, pathogens,and pesticides to small streams and larger rivers. Our objective was to design, build, and evaluate a drainage channelresearch facility for examining water quality impacts of water management in open-channel. An open-channel research facilityincorporating a paired design was constructed during 2002 near Lamberton, Minnesota. A 200-m reach of existing drainagechannel was converted into a system of four parallel channels. The facility was equipped with water level control devicesand instrumentation for flow monitoring and water sample collection on upstream and downstream ends of the system. Flowhydrographs were created by simulating flow generated by pumping water from an adjacent pond. Channel morphology wasdescribed by measuring longitudinal channel bottom elevation and cross-sectional channel profiles. Hydrographs from simulatedflow events during year one indicated that the paired open channels responded similarly to changes in inflow. Variabilityin hydrologic response between the open-channels was attributed to differences in open-ditch channel bottom elevation andvegetation density. Research facility system performance exceeded expectations. Potential future benefits of this research includeimproved biological diversity and integrity of open-channel ecosystems, reduced flood peaks and increased flow duringcritical low-flow periods, improved and more efficient nitrogen retention within the open-channel ecosystem, and decreasedmaintenance cost associated with reduced frequency of channel maintenance.