Livestock Grazing and Riparian Habitat Water Quality: An Examination of Oak Woodland Springs in the Sierra Foothills of California1

Studies throughout the western United States have shown that livestock can degrade riparian vegetation and stream channels and produce sediment, pathogen, and nutrient loading. This study at the Sierra Foothill Research and Extension Center is the first to focus on effects of livestock grazing on hardwood rangeland springs and associated riparian resources. Cattle grazing treatments at three intensities were applied in 1to 2.5-ha pastures, which included a spring and ephemeral creek. Over a 5-year period we monitored nitrate, orthophosphate, dissolved oxygen, temperature, and pH. Results show no significant differences in measured parameters among treatments. Sites were the source of some significant differences. This study indicates that moderate livestock grazing intensities do not detrimentally affect water quality at springs or ephemeral creeks in the oak woodlands of California. Riparian systems, including springs, seasonal and perennial streams, and shoreline vegetation, comprise an important and unique component in oak (Quercus spp.) woodland habitat and are crucial considerations in land management (Ewing and others 1988, Platts and others 1987). California’s Mediterranean climate, with a summer drought period of 5-8 months, results in hardwood rangelands dominated by introduced annual grasses, varying amounts of native perennial grasses, and native oak species. Hardwood rangelands provide 75 percent of the forage used by the State’s range livestock industry, in addition to furnishing many species with a source of water and habitat (Ewing and others 1988). Thus riparian patches provide critical sources of water for humans, wildlife, and livestock, and unique habitat and diversity of plant and animal species. Western riparian zones in general are suggested to be the most productive habitats in North America (Johnson and others 1977). However, development of these fertile environments, such as in the Central Valley of California, has resulted in massive conversion or degradation of these systems (Franzreb 1987). Spring systems have historically been developed to provide water for domestic uses. It has been suggested that livestock grazing is a major cause of riparian habitat disturbance (Fleischner 1994, Kauffman and Krueger 1984). Cattle seek riparian habitat for shade, cool temperatures, water, and abundant forage supplies. Livestock may directly affect the physical condition of riparian areas as well as directly or indirectly degrade water quality. Physical disturbance parameters include streamside vegetation, channel morphology, and the soil structure (Kauffman and Krueger 1984, Platts 1981, Platts and Nelson 1989). Water quality degradation includes chemical changes such as nutrient loading and physical changes such as increased flow and turbidity (Stednick 1991). At the watershed level, nonpoint source pollution may be observed as diffuse changes in the water quality and runoff quantity. Livestock may compact soil, decreasing infiltration and increasing overland flow which may result in erosion and sedimentation. Wood and others (1989) found that mean infiltration rates were significantly greater on treatments excluded from livestock grazing. Wood also found infiltration rates and quality 1An abbreviated form of this paper was presented at the Symposium on Oak Woodlands: Ecology, Management, and Urban Issues, March 19-22, San Luis Obispo, Calif. 2Graduate student and range ecologist, respectively, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720.