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Title: Weir Design and Calibration for Stream Monitoring in a Riparian Wetland

item Hively, Wells - Dean
item McCarty, Gregory

Submitted to: Hydrological Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2006
Publication Date: 12/31/2006
Citation: Hively, W.D., McCarty, G.W., Angier, J.T., Geohring, L.D. 2006. Weir design and calibration for stream monitoring in a riparian wetland. Hydrological Science and Technology. 22(1-4):71-82.

Interpretive Summary: Five stream flow monitoring weirs were designed and installed in a riparian wetland located in a USDA-ARS watershed study site in Beltsville, MD (the Optimizing Production Inputs for Economic and Environmental Enhancement, OPE3, research watershed). The flat topography and shallow stream depth associated with the wetland created challenging conditions for stream weir implementation, and required several departures from optimum weir design parameters. This paper details the process by which the weirs were calibrated through the use of on-site measurement data. Results demonstrate that accurate rating curves can be obtained with proper calibration measurements even when design is non-ideal. The discharge rating curves developed by this project will assist in ongoing projects at the OPE3 watershed, such as the evaluation of phosphorus mass balance and linkages to pesticide transport.

Technical Abstract: Accurate measurement of stream flow is an important component of environmental water quality monitoring. Flow rates in small streams can be conveniently monitored using weirs. The objective of this study was to design, install, and calibrate a series of permanent compound weirs for use in monitoring flow and water quality in a first order riparian wetland stream that exhibited great variability in flow (five orders of magnitude). The site was located at the USDA-ARS Beltsville Agricultural Research Center in the mid-Atlantic coastal plain of Maryland, and the stream monitoring stations supported a variety of environmental research into hydrological transport and transformation of nutrients and agrochemicals at a landscape scale. The low-relief setting (0.7% slope), shallow stream depth, tendency for flooding, and necessity to avoid ecosystem alteration created challenging conditions for stream weir implementation. A compound V-notch / Cipolletti design successfully measured all but the highest flows (flood stage). Calibration of each weir based on field measurements was necessary to compensate for required compromises in weir design.