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Preferential Flow Caused by Past Disturbance in a Restored Riparian Wetland

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

Citation:  Pp. 61-64 in Preferential Flow, Water Movement and Chemical Transport in the Environment, Proc. 2nd Int. Symp. (3-5 January 2001, Honolulu, Hawaii, USA), eds. D. D. Bosch and K. W. King. St. Joseph, Michigan: ASAE  701P0006.(doi:10.13031/2013.2141)
Authors:   G. Vellidis, R. Lowrance, R.K. Hubbard, and P. Gay
Keywords:   Riparian buffer, Wetland, Nitrate plumes, Preferential flow, Bypass

A restored riparian wetland is being evaluated as a bioremediation site for nutrients and pesticides moving downslope from agricultural uplands. In 1985, the mature riparian forest on the site was clear cut and the wetland converted to a wet pasture for grazing. A limited network of ditches was excavated to improve drainage. Over time, the ditches were filled by eroded sediments. In 1991, the wetland was restored by reintroducing a combination of native trees and grasses. An intensive monitoring program using a network of shallow ground water monitoring wells was established to measure agrochemical movement through the wetland in shallow ground water and surface runoff. Data from ground water were analyzed for NO3-N, and Cl concentrations. Conventional statistical analyses showed the wetland was very effectively attenuating nutrient concentrations. Analyses with geostatistics showed distinct preferential flow paths through the wetland that permitted nutrient plumes to bypass the attenuating capacity of the biologically active root zone. Further analyses indicated that the preferential flow paths coincided with the old ditch network. This study provides a lesson on the difficulties of overcoming significant wetland disturbance and restoration in general.

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