Microbial Water Quality Conditions Associated with Livestock Grazing, Recreation, and Rural Residences in Mixed-Use Landscapes

Abstract

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.

Rotational grazing can mitigate ecosystem service trade‐offs between livestock production and water quality in semi‐arid rangelands

“…A growing number of studies examining climate effects on water quality have found E. coli levels in streams and other waterbodies are correlated with ambient air temperature (Whitman & Nevers, 2008; Xu et al., 2019). Maximum bacterial concentrations often occur during the warmest part of the year (Cha et al., 2016; Derose et al., 2020), potentially driven by the ability of E. coli to reproduce rapidly in warmer waters (Guber et al., 2015). Our study suggests that this might be happening across our sites, and that having cattle present during the warmest part of the year when levels of E. coli are at their peak, can increase the chance of violating regulatory water quality benchmarks.…”

Determination of Heavy Metals in Irrigation Water, Soil, Paddy, and Produced Rice of Some Paddy Fields of Iraq

“…The samples were placed in clean, dry containers and stored in an ice bath until subsequent analysis. [28].…”

Economic Effects of Federal Grazing Programs

“…Previous work has highlighted the environmental impacts of grazing (e.g., Vincent 2019). Grazing on federal land comes with a mix of costs, such as declines in water quality (Delrose et al 2020) and emissions (Wang et al, 2020), but may also have environmental benefits such as reductions in the risk of wildfire (Davies et al, 2016; Davies et al 2022). The coefficients reported in this paper can help further evaluate the costs and benefits of federal grazing, as well as expand to other sectors of the economy.…”