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An Overland Flow Sampler for Use in Vegetative Filters

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  022050,  2002 ASAE Annual Meeting   . (doi: 10.13031/2013.17643) @2002
Authors:   D. Eisenhauer, M. Helmers, J. Brothers, M. Dosskey, T. Franti, A. Boldt, B. Strahm

Vegetative filters (VF) are used to remove contaminants from agricultural runoff and improve surface water quality. Techniques are needed to quantify the performance of VF in realistic field settings. The goal of this project was to develop and test a relatively simple and low cost method for sampling overland flow in a VF. The 0.3 m wide sampler has the capacity to sample a flow rate of 1.3 L/s and a total runoff volume of about 20 000 L. The sampler was tested in the laboratory, in field experiments, and using a simulation model. Overall the sampler split ratio (SR) is 2180. The SR is essentially constant with flow rate in the range of 0.1 to 1.0 L/s. Computer simulations of overland flow using MIKE SHE indicate that the sampler does not cause significant convergence or divergence of flow when sampling at the downstream edge of the VF. Because of the higher roughness in the VF relative to the row-cropped contributing watershed, longer wing walls are needed to avoid flow convergence when sampling at the leading edge of the buffer. The required length of the wingwall is dependent on land slope, flow rate, and the hydraulic roughness of the filter. The runoff volume and runoff hydrographs that were derived from the sampler agreed well with the measurements taken with flow measurement flumes. Equations were developed to help interpret the data collected with the sampler.

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