Biology Reference
In-Depth Information
with state water managers to re-create healthier conditions for cotton-
wood growth along the Sacramento.
Along smaller rivers, Californians have been busy mending some of
the damage created by the mining of sand, gravel, and gold. The Tuolumne
River—one of three large Sierra tributaries of the once-mighty San Joa-
quin—had worked itself into a particularly deep rut since it was dammed
for hydropower in the 1800s, and then again for San Francisco's water sup-
ply in 1923. It was also heavily mined for gravel. Restoration projects have
since filled huge offshore lakes and in-stream pits left by mining, and rein-
troduced some natural river topography.
River restoration in the bay watershed has also involved the removal of
dozens of small dams, poorly designed culverts, bridges, and other barri-
ers. The organization American Rivers estimates that in the last decade, 15
barriers between five and ten feet high have been removed from Bay Area
streams, and about the same number in the Central Valley. The largest re-
moval to date may have been the demolition of the 20-foot-high, 184-foot-
wide McCormick-Saeltzer Dam on Clear Creek, a Sacramento River trib-
utary, in 2000.
To get an inkling of how rivers might have functioned before dams,
scientists study the Cosumnes River. It is the only completely free-flowing
river left in the bay's watershed. Here, they've been experimenting with
reconnecting rivers to their historic floodplains. Researchers have found
that floodplains once varied in elevation by as much as three yards, con-
trary to the laser-level flat topography of today's surrounding farm fields.
These natural nuances may be important in restoring variety to riverine
habitats.
If the Cosumnes is distinctive as the last free-flowing river in the sys-
tem, the San Joaquin is known as the river with little or no flow at all. For
decades, so much of the San Joaquin's natural flow has been diverted that
the riverbed runs dry for many miles between the Friant Dam and the
confluence of the Merced River.
After a 20-year legal battle, the river and its extirpated salmon may get
a chance at rebirth. In 2006 a settlement of the litigation was achieved, and
in 2009 Congress approved federal funding for the next major landscape-
scale restoration in the system. “It will turn what is a dead river into a live
one, and reintroduce salmon to the state's second largest river,” says Tina
Swanson, whose organization helped the Natural Resources Defense
Council champion the cause in court. “Neither winter-run nor spring-run
Chinook Salmon will recover from the brink of extinction until we estab-
lish additional populations in other rivers.” The San Joaquin got its first
official restoration flows under the settlement in 2009-2010 and, as of this
writing, salmon were to be reintroduced in 2012.
