Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

and grazing. Dams and water diversions are also common. These physical changes
resulted in water temperatures too high to sustain salmonid populations. The Salmon
River, however, is comparatively pristine; some reaches are designated as Wild and
Scenic Rivers. The main cause of riparian loss in the Salmon River basin is likely wild
fires – the effects of which have been exacerbated by salvage logging (NRC 2003).
Mining
Famous for the gold rush of the mid-1800s, California has a long history of mining.
Extraction methods such as suction dredging, hydraulic mining, strip mining may cause
water pollution problems. In 2004, California ranked top in the nation for non-fuel
mineral production with 8.23% of total production (NMA 2007). Today, gold, silver, and
iron ore comprise only 1% of the production value. Primary minerals include
construction sand, gravel, cement, boron, and crushed stone. California is the only state
to produce boron, rare-earth metals, and asbestos (NMA 2007).
California contains some 1,500 abandoned mines. Roughly 1% of these mines are
suspected of discharging metal-rich waters into the basins. The Iron Metal Mine in the
Sacramento Basin releases more than 1,100 lbs of copper and more than 770 lbs of zinc
to the Keswick Reservoir below Shasta Dam. The Iron Metal Mine also released
elevated levels of lead (Cain et al. 2000 in Carter and Resh 2005). Metal contamination
reduces the biological productivity within a basin. Metal contamination can result in fish
kills at high levels or sublethal effects at low levels. Sublethal effects include a reduction
in feeding, overall activity levels, and growth. The Sacramento Basin and the San
Francisco Bay watershed are two of the most heavily impacted basins within the state
from mining activities. The basin drains some of the most productive mineral deposits in
the region. Methylmercury contamination within San Francisco Bay, the result of 19 th
century mining practices using mercury to amalgamate gold in the Sierra Nevada
Mountains, remains a persistent problem today. Based on sediment cores, pre-mining
concentrations were about five times lower than concentrations detected within San
Francisco Bay today (Conaway, Squire et al. 2003).
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