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

Sacramento River Basin: NAWQA analysis
Another study conducted by the USGS from 1996-1998 within the Sacramento River
Basin detected up to 24 out of 47 pesticides in surface waters (Domagalski 2000).
Pesticides included thiobencarb, carbofuran, molinate, simazine, metolachlor, dacthal,
chlorpyrifos, carbaryl, and diazinon. Land use differences between sites are reflected in
pesticide detections. Carbofuran was detected in 100% of samples from the agricultural
site, but only 6.7% of urban samples (Domagalski 2000). Carbaryl, however, was
detected in 100% of urban samples and 42.9% of agricultural samples. Some pesticides
were detected at concentrations higher than criteria for the protection of aquatic life in the
smaller streams, but were diluted to safer levels in the mainstem river. Intensive
agricultural activities also impact water chemistry. In the Salinas River and in areas with
intense agriculture use, water hardness, alkalinity, nutrients, and conductivity are also
high.
Habitat Modification
The Central Valley area, including San Francisco Bay and the Sacramento and San
Joaquin River Basins, has been drastically changed by development. Salmonid habitat
has been reduced to 300 miles from historic estimates of 6,000 miles (CDFG 1993). In
the San Joaquin Basin alone, the historic floodplain covered 1.5 million acres with 2
million acres of riparian vegetation (CDFG 1993). Roughly 5% of the Sacramento River
Basin’s riparian forests remain. Impacts of development include loss of LWD, increased
bank erosion and bed scour, changes in sediment loadings, elevated stream temperature,
and decreased base flow. Thus, lower quantity and quality of LWD and modified
hydrology reduce and degrade salmonid rearing habitat.
The Klamath Basin in Northern California has been heavily modified as well. Water
diversions have reduced spring flows to 10% of historical rates in the Shasta River, and
dams block access to 22% of historical salmonid habitat. The Scott and Trinity Rivers
have similar histories. Agricultural development has reduced riparian cover and diverted
water for irrigation (NRC 2003). Riparian habitat has decreased due to extensive logging
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