Increasing hydrogen ion activity of water in two reservoirs supplying the San Francisco Bay Area, California

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Abstract
The hydrogen ion activity (H+) of water in two Sierra Nevada reservoirs (Pardee and Hetch Hetchy) that supply the San Francisco Bay area has been increasing with time over the period 1954–1979. This conclusion is based on weekly measurements ofpH at the two reservoirs and is supported by measurements of alkalinity which decreased at Pardee over the period 1944–1979. Based on linear models, the rate of the increasing (H+) was the same at both reservoirs, and (H+) varied concomitantly from year to year, suggesting a common, general cause. Mean monthly variation in (H+) corresponded to mean monthly variation in atmospheric pollution from a nine‐county area around San Francisco Bay. The most likely cause of the increasing (H+) of reservoir waters is NOx from automobile exhausts primarily from the San Francisco Bay area.