Geoscience Reference
In-Depth Information
l ood control during the wet season with water storage for the dry summer
and fall months.
coastal impacts
By the year 2050, when the average global temperature is predicted to be about
2°F higher than it was at the turn of the twenty-i rst century, scientists are fore-
casting a number of other changes in the West that will directly or indirectly
af ect the water supply. For instance, current predictions indicate that sea lev-
els along the Pacii c coast will rise about thirteen inches or more due to melt-
ing ice and thermal expansion resulting from the increased heat absorption by
the ocean surface. Rising sea levels will inundate coastal wetlands. h e more
protected parts of the coastline—bays and estuaries like San Francisco Bay
and Puget Sound—will grow larger and saltier with the rising sea, encroaching
on the low-lying bordering cities. Around these estuaries, the tidal marshes
that had so long been part of the natural history will be squeezed out.
More insidious, though, will be the intrusion of saline water into under-
ground freshwater aquifers that now provide much of the region's drinking
and irrigation water. Coastal ground waters are also at risk of becoming
saltier as sea levels rise.
In California's Sacramento-San Joaquin Delta, higher sea levels may
cause levees to fail, drowning the surrounding low-lying valleys. By 2050,
two-thirds of the state's projected 50 million residents may live in the south-
ern Central Valley and Southern California, areas that depend on the fresh-
water that passes through the delta and is pumped southward through the
California Aqueduct. Should the levees fail, two-thirds of the state will be
let without a signii cant amount of their potable water.
increased risk of dam failures
h ose who live on l oodplains are no longer the only ones at risk of cata-
strophic l oods. h e twentieth-century dams hold back vast reservoirs of
water, and they have the potential to fail, with catastrophic results. Southern
California already experienced a taste of this in 1928, when the St. Francis
Dam collapsed, resulting in hundreds of deaths. It was the worst civil engi-
neering disaster of the century in the United States.
