Human Influences on San Francisco Bay - Like all urban estuaries in the world, San Francisco Bay receives toxic substances from a variety of natural and human sources. Studies here focus on characterizing the interrelated physical, chemical, and biological processes that affect contamination within the Bay and the delta ecosystems. Results of these studies are providing an understanding of the effects of contamination on species throughout the food chain and of the effectiveness of resource-management strategies. San Francisco Bay is affected by urban runoff, industrial and municipal discharges, and agricultural runoff from nearby fertile river valleys. Research is focusing on the processes that affect migration of contamination within the watershed and the resulting effects on the ecosystem.
Studies are under way in two areas with differing climate and hydrologic settings.
The results and methods developed at these sites are being used and demonstrated through the USGS Abandoned Mine Lands Initiative. Stream tracer methods, which were developed and tested in the upper Arkansas River, Colorado , have enabled identification of specific sources of stream contamination. In this arid area, contaminants often are transported great distances by ground water, and may threaten regional water supplies. At Pinal Creek, Arizona , scientists are studying the geochemical evolution of a plume of metals-laden ground water and its ultimate interaction with Pinal Creek. Silverton, Colorado, at the mouth of the upper Animas River and its watershed in the background, where over 1,500 abandoned mine sites affect water and ecosystem quality.