Management Scale Assessment of Practices to Mitigate Cattle Microbial Water Quality Impairments of Coastal Waters
University of California Cooperative Extension, Novato, CA 94947, USA
Point Reyes National Seashore, Point Reyes Station, CA 94956, USA
Department of Agricultural and Resource Economics, University of California, Davis, CA 95616, USA
Department of Plant Sciences, University of California, Davis, CA 95616, USA
Author to whom correspondence should be addressed.
Sustainability 2019, 11(19), 5516; https://doi.org/10.3390/su11195516
Received: 12 August 2019 / Revised: 30 September 2019 / Accepted: 2 October 2019 / Published: 6 October 2019
(This article belongs to the Collection Eutrophication and Sustainable Management of Water)
Coastal areas support multiple important resource uses including recreation, aquaculture, and agriculture. Unmanaged cattle access to stream corridors in grazed coastal watersheds can contaminate surface waters with fecal-derived microbial pollutants, posing risk to human health via activities such as swimming and shellfish consumption. Improved managerial control of cattle access to streams through implementation of grazing best management practices (BMPs) is a critical step in mitigating waterborne microbial pollution in grazed watersheds. This paper reports trend analysis of a 19-year dataset to assess long-term microbial water quality responses resulting from a program to implement 40 grazing BMPs within the Olema Creek Watershed, a primary tributary to Tomales Bay, USA. Stream corridor grazing BMPs implemented included: (1) Stream corridor fencing to eliminate/control cattle access, (2) hardened stream crossings for cattle movements across stream corridors, and (3) off stream drinking water systems for cattle. We found a statistically significant reduction in fecal coliform concentrations following the initial period of BMP implementation, with overall mean reductions exceeding 95% (1.28 log10)—consistent with 1—2 log10 (90–99%) reductions reported in other studies. Our results demonstrate the importance of prioritization of pollutant sources at the watershed scale to target BMP implementation for rapid water quality improvements and return on investment. Our findings support investments in grazing BMP implementation as an important component of policies and strategies to protect public health in grazed coastal watersheds.