Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2007
Publication Date: 6/20/2008
Citation: Kroger, R., Cooper, C.M., Moore, M.T. 2008. A preliminary study of an alternative controlled drainage strategy in surface drainage ditches: low-grade weirs. Agricultural Water Management. 95(6):678-684. Interpretive Summary: Successful agricultural land use requires proper drainage from production fields. This drainage may contain a variety of pollutants, including sediment, pesticides, and nutrients. Vegetated drainage ditches have been shown to be beneficial in the mitigation of such pollutants if a sufficient amount of retention time is available. The current study examined the use of low-grade weirs in vegetated and unvegetated drainage systems to increase ditch retention time, allowing for more processing of potential contaminants. Results indicated the vegetated weir increased the time it took for the test pollutant (NaCl) to peak within the system, and it also reduced the peak concentration when compared to unvegetated weirs. By focusing on hydrological manipulations within drainage ditch systems, improved mitigation of non-point source pollutants can occur.
Technical Abstract: This study examined hydrological characteristics of low-grade weirs, an alternative controlled drainage strategy in surface drainage ditches. Hydrographs of vegetated and clear scraped (control) replicates of weir vs. non-weir treatments were compared to determine differences in time to peak (Tp) and time to base (Tb). Drainage ditches Tp and Tb were affected by both vegetation and weir presence. The order of treatment efficiency for Tp was observed to be: control non-weir < vegetated non-weir < control weir < vegetated weir. Furthermore, Tb for each ditch was the reciprocal relationship from Tp where vegetated weir > control weir > vegetated non-weir > control non-weir. Low-grad weirs increase HRT (vegetated and clear scraped) and future research in water quality improvement and weir management will yield useful information for nonpoint source pollutant reduction.