Impacts of Riparian Buffer Zones on Stream Water Quality: A Quantitative Assessment in the Catalpa Creek Watershed

Author(s): Ramirez-Avila, J.; Grafe, J.; Schauwecker, T.; Ortega-Achury, S.; Martin, J.; Noble, T.; Czarnecki, J.

Riparian buffer zones importantly affect stream water quality and its ecosystem’s structure and function. A study was conducted to determine if there is a measurable difference in water quality conditions between forested or grassed riparian zones along tributaries of the Catalpa Creek Watershed. The study considered field data and laboratory analysis. Weekly monitoring was performed at 18 stations along the tributaries during fall 2017. The study reaches consisted of an upstream segment covered by a forested riparian zone and a downstream segment in which grass grew and was mowed along both sides of the stream. Stream water temperature along the forested riparian segments were lower (13.9°C to 27°C) than those along the grassed riparian zones (15.0°C to 31.5°C). The differences in water temperature between forested and grassed riparian zones were smaller as the air temperature decreased during the late fall season. Overall, the instantaneous concentration of dissolved oxygen (DO) along the reaches was always higher than 6 mg l-1, a higher concentration than the standard proposed by MDEQ (5.0 mg l-1). The DO concentration along the stream was sometimes higher for grassed riparian zones, which can be attributed to reaeration caused by an abrupt change in slope, depth and flow velocity downstream of the forested riparian zone. However, DO concentrations at the end of the grassed riparian segments reached similar or lower values than those observed along the forested riparian segment. No adverse impacts on water quality were caused on the monitored reaches due to levels and temporal or spatial variability of pH in the stream water. The spatial variability of pH appears to be consistent with the spatial variability of DO concentrations for all the studied reaches. Forested riparian zones can reduce stream water temperatures and maintain favorable DO concentrations and pH, with a biological significance for living organisms in the stream. Consequently, establishment and maintenance of forested riparian zones might provide benefits in mitigating adverse impacts on stream ecology and water quality.

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