USDA Forest Service

Pacific Southwest Research Station


Pacific Southwest Research Station
800 Buchanan Street
West Annex Building
Albany, CA 94710-0011

(510) 559-6300

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Programs and Projects


Sierra Nevada Research Center

Water and Watershed Processes

Improved knowledge of aquatic and land interactions at local and watershed scales is essential to evaluate and design land management alternatives for stream and watershed resources. Sixty percent of California's water originates from small streams in the Sierra Nevada, yet very little information is known about how these streams are affected at the source by land management activities such as dams, diversions, logging, etc.The quality of aquatic and riparian (near-stream) ecosystems associated with streams is directly related to the condition of adjacent uplands within their watersheds. The degradation of forest streams and their associated watersheds is often the result of non-point sources such as past timber harvesting, roads, fire suppression, catastrophic wildfires, and atmospheric deposition. Restoration of the Sierra Nevada's forest watersheds to historic or desired conditions requires active management such as reintroduction of frequent, cool fires and removal of accumulated fuel loads.

This problem area can address the multiple stressors often acting on aquatic ecosystems in forests: tree thinning/harvesting, fire, air pollution, climate variability, land use change, water diversion, grazing, and roads. The land managed by the Forest Service provides much of the source water that other organizations address once the water gets to California's central valley and coast.

blue arrrowKings River Experimental Watershed

Subproblem 1: Structure and Function of Sierra Nevada headwater streams and their associated watersheds.

A suite of physical, chemical, and biological measurements is necessary to understand how watersheds function and respond to both natural and anthropogenic stress or disturbance. Since not every parameter of interest can be measured, a set of characteristics is selected to represent physical, chemical, and biological structure and function. A good understanding of the variability in and interaction between these characteristics is necessary to evaluate change over time and response to management treatments.

Subproblem 2: Stream and watershed response to forest restoration.

The Sierra Nevada landscape has been altered in many ways since the 1850s with selective timber harvesting, a century of fire suppression, extensive domestic animal grazing, and more recently increasing and diverse recreation. In addition, climate is changing and restoration back to a desired historic condition may not be entirely possible. Cause and effect experiments are necessary to know the effectiveness of restoration practices and reduce concerns about negative effects. Fire has been suppressed in the Sierra Nevada for about 100 years, thus a combination of thinning and prescribed fire is needed to efficiently move the forest condition towards a pre-suppression condition of larger trees with a canopy closure greater than 50% and an open understory. Desired forest characteristics are uneven-aged stands of a patchy nature.

Subproblem 3: Forest Best Management Practices for aquatic ecosystems.

Concerns exist about negative impacts to water quality and aquatic ecosystems from forest management and restoration activities. 100 years of fire suppression and historic land management practices have created forests with high fuel loads and overstocked conditions. Many small, suppressed trees exist now rather than fewer large trees per unit area that are known to have occurred in pre-settlement forests. Much of the information on fire effects comes from hot, wildfire situations that result in these densely stocked contemporary forests of the west. Usually these studies do not have before and after data and have to use after-the-event controls. Similarly much of the data on silviculture effects comes from severe treatments such as clear cuts, seed-tree cuts, or shelter-wood cuts and is predominantly from different geologic and climatic ecosystems like the Pacific Northwest. Thus the current measures to mitigate effects on aquatic ecosystems may be inappropriate for Sierra Nevada streams.

Last Modified: Mar 28, 2013 02:53:37 PM