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Effects of Livestock Exclusion and Stream Restoration on the Water Quality of a North Carolina Stream

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

Citation:  Transactions of the ASABE. 58(6): 1547-1557. (doi: 10.13031/trans.58.11205) @2015
Authors:   Daniel E. Line
Keywords:   Best management practice, Stream restoration, Water quality monitoring.

Abstract. The objective of this project was to document the effect of livestock exclusion and stream restoration on the water quality of two streams. Water quality monitoring was conducted prior to and after the installation of livestock exclusion fencing and varying degrees of stream restoration on the two streams. The monitored reaches of both streams were located in a dairy cow pasture with the same management in that, prior to fencing and stream restoration (pre-BMP) implementation, cows had unlimited access to the stream channel and after (post-BMP) the cows were fenced out. Rainfall and discharge were monitored continuously, and flow-proportional samples were collected upstream and downstream of the two monitored reaches during storm events. Non-storm grab samples were also collected at each monitoring station. Samples were analyzed for nitrogen, phosphorus, and sediment concentrations. Water quality monitoring occurred for approximately three years prior to (pre-BMP) and 1.7 years following (post-BMP) fencing and stream restoration. Livestock exclusion fencing and limited stream restoration on a 488 m long reach of one stream resulted in statistically significant reductions in total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), total phosphorus (TP), and total suspended residue (TSR) storm event loads of 41%, 59%, 54%, and 67%, respectively, compared to the pre-BMP loads. However, the proportion of the reduction attributable to exclusion fencing, stream restoration, or fewer cows in the pasture could not be determined. The second stream had a full restoration in that the streambed was raised, moved, and completely reconstructed over the entire 134 m long monitored reach. Post-BMP monitoring documented significant differences in NH3-N (decreased), and NOx-N (increased) loads and no change in TKN, TP, TSR, and total nitrogen (TN) loads from the upstream to the downstream monitoring station. These results indicated that there was no significant treatment effect of the restored stream channel on instream pollutant loads.

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