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

Hydromodification Projects
Several of the rivers within the area have been modified by dams, water diversions,
drainage systems for agriculture and drinking water, and some of the most drastic
channelization projects in the nation (see species distribution maps). In all, there are
about 1,400 dams within the State of California, more than 5,000 miles of levees, and
more than 140 aqueducts (Mount 1995). In general, the southern basins have a warmer
and drier climate and the more northern, coastal-influenced basins are cooler and wetter.
About 75% of the runoff occurs in basins in the northern half of California, while 80% of
the water demand is in the southern half. Two water diversion projects meet these
demands—the federal Central Valley Project (CVP) and the California State Water
Project (CSWP). The CVP is one of the world’s largest water storage and transport
systems. The CVP has more than 20 reservoirs and delivers about 7 million acre-ft per
year to southern California. The CSWP has 20 major reservoirs and holds nearly 6
million acre-ft of water. The CSWP delivers about 3 million acre-ft of water for human
use. Together, both diversions irrigate about 4 million acres of farmland and deliver
drinking water to roughly 22 million residents.
Both the Sacramento and San Joaquin rivers are heavily modified, each with hundreds of
dams. The Rogue, Russian, and Santa Ana rivers each have more than 50 dams, and the
Eel, Salinas, and the Klamath Rivers have between 14 and 24 dams each. The Santa
Margarita is considered one of the last free flowing rivers in coastal southern California.
Nine dams occur in this watershed. All major tributaries of the San Joaquin River are
impounded at least once and most have multiple dams or diversions. The Stanislaus
River, a tributary of the San Joaquin River, has over 40 dams. As a result, the
hydrograph of the San Joaquin River is seriously altered from its natural state. Alteration
of the temperature and sediment transport regimes had profound influences on the
biological community within the basin. These modifications generally result in a
reduction of suitable habitat for native species and frequent increases in suitable habitat
for nonnative species. The Friant Dam on the San Joaquin River is attributed with the
extirpation of spring-run Chinook salmon within the basin. A run of the spring-run
Chinook salmon once produced about 300,000 to 500,000 fish (Carter and Resh 2005).
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