Project at a Glance

Title: Episodic acidification of lakes in the Sierra Nevada.

Principal Investigator / Author(s): John L. Stoddard

Contractor: US EPA

Contract Number: A132-048

Research Program Area: Atmospheric Processes, Ecosystem & Multimedia Effects

Topic Areas: Acid Deposition, Ecosystem Impacts, Field Studies, Impacts, Monitoring


The lakes and streams of the Sierra Nevada mountains are vulnerable to acidic deposition because of the predominance of granitic rocks and thin acidic soils in their catchments, and the large quantity of precipitation in the region. Ten lakes and their watersheds were chosen for intensive monitoring. During two snowmelt and summer runoff seasons, automated samplers were installed at each lake outlet, along with stream gauging equipment and automated data recorders. Outlet samples were collected for chemical analysis, and discharge measurements were recorded. This study confirmed that nitrate is the key elements controlling episodic acidification in Sierran watersheds. This study also found that episodic acidification can occur in high elevation Sierran watersheds, but only in the most extreme conditions. Lake watersheds most likely to be affected by episodic acidification have extreme elevation, little or no soil development, low summer acid neutralizing capacity, and extensive granitic talus.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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