Contamination of surface waters with microbial pollutants from fecal sources is a significant human health issue. Identification of relative fecal inputs from the mosaic of potential sources common in rural watersheds is essential to effectively develop and deploy mitigation strategies. We conducted a cross-sectional longitudinal survey of fecal indicator bacteria (FIB) concentrations associated with extensive livestock grazing, recreation, and rural residences in three rural, mountainous watersheds in California, USA during critical summer flow conditions. Overall, we found that 86% to 87% of 77 stream sample sites across the study area were below contemporary Escherichia coli-based microbial water quality standards. FIB concentrations were lowest at recreation sites, followed closely by extensive livestock grazing sites. Elevated concentrations and exceedance of water quality standards were highest at sites associated with rural residences, and at intermittently flowing stream sites. Compared to national and state recommended E. coli-based water quality standards, antiquated rural regional policies based on fecal coliform concentrations overestimated potential fecal contamination by as much as four orders of magnitude in this landscape, hindering the identification of the most likely fecal sources and thus the efficient targeting of mitigation practices to address them.
Optimising the spatial distribution of free-ranging livestock is a significant challenge in expansive, grazed landscapes across the globe. Grazing managers use practices such as herding (i.e. droving), strategic placement of offstream livestock drinking water and nutritional supplements, and strategic fencing in attempts to distribute livestock away from sensitive streams and riparian areas. We conducted a cross-sectional survey of 46 cattle-grazed riparian areas and associated stream reaches embedded in rugged range landscapes to examine relationships between implementation of these management practices, stocking rate, and riparian health. We determined in-stream benthic invertebrate assemblages at each site to serve as an integrative metric of riparian health. We also collected information from the grazing manager on stocking rate and implementation of livestock distribution practices at each site over the decade before this study. Off-stream livestock drinking-water sources were implemented at just two sites (4.3%), indicating that this was not a common distribution practice in these remote management units. We found no significant relationship of riparian health (i.e. invertebrate richness metrics) with stocking rate (P $ 0.45 in all cases), or with the simple implementation (yes/no) of off-stream nutritional supplements, fence maintenance, and livestock herding (P $ 0.22 in all cases). However, we did find significant positive relationships between riparian health and managerial effort (person-days spent per year for each individual practice) to implement off-stream nutritional supplements and fence maintenance (P # 0.017 in all cases). Livestock herding effort had an apparent positive association with riparian health (P $ 0.2 in all cases). Results highlight that site-specific variation in managerial effort accounts for some of the observed variation in practice effectiveness, and that appropriate managerial investments in grazing distributional practices can improve riparian conditions.
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