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Water quality: Effects of natural and anthropogenic disturbances.
Amacher, Michael*,1, Kotuby-Amacher, Janice2, Grossl, Paul2, 1 USDA Forest Service, Logan, Utah2 Utah State University, Logan, Utah
ABSTRACT- Water quality in natural forest and range ecosystems is influenced by many factors including catchment lithology, vegetation, streamflow (controlled by episodic climate events), land use activities (e.g., mining, grazing, and recreational activites), natural disturbances (e.g., wildfires), and land management activities (prescribed burning for fuel reduction and plant community conversion). A survey of water quality in the Monitor, Toquima, and Toiyabe mountain ranges of central Nevada was conducted in the spring of 1994. A more detailed follow-up survey of streams in the Toiyabe Range was conducted in 1995 through 1998. In preparation for a prescribed burn, baseline water quality data were collected in the Shoshone Range in 1999 through 2001. Large-scale and within catchment spatial treands in water quality parameters were used to evaluate the effects of catchment lithology on stream water composition. Seasonal and annual changes in stream water composition were also quantified. These water quality surveys were used to asses the relative importance of catchment lithology, climate, and land use and management activities as controls of water quality in central Nevada catchments. Catchment lithology is the primary regulator of the chemical composition of streams in central Nevada. Streamflow also influences stream chemical composition seasonally and annually (wet versus dry years). For the period measured, stream chemical composition was not influenced by land use activities except for the Reese River. Because stream chemical compositon is being regulated by catchment lithology and streamflow (climate driven), this indicator of water quality may be sensitive to anthropogenic inputs in some catchments should land use activities change (e.g., changing grazing or fire regimes). Chemical composition of streams is not sensitive to current land use activities.
KEY WORDS: water quality, catchment lithology, streamflow, land use