Geoscience Reference
In-Depth Information
Regardless of cause and ef ect with respect to population, the fact remains
that the monumental changes to the region's natural rivers, lakes, and wet-
lands have wreaked havoc on the natural aquatic ecosystems that these
waters harbored. h e plants and animals that depend on streams, lakes, and
wetlands declined rapidly over the twentieth century due to large-scale land
and water development in the West. Hundreds of species that are federally
listed as threatened or endangered depend on rivers and streams. Over three-
quarters of the native freshwater i sh in the West are either extinct already
or listed as endangered.
Human existence in the West relies not just on water resources but also
on these other natural resources—the plants and animals—that the water
sustains. h e West is at a crossroads today as the human population in the
region continues to increase, controlling ever more of the limited freshwater
at the expense of aquatic ecosystems. Massive and profound as these public
works are, they have been part of life in the West for so long that people
are almost unaware of them. Few would voluntarily go back to the pre-
hydraulic era, when water was unreliable from year to year and much of
the agricultural industry would not have been possible. However, water
development has come with a steep price to the environment—particularly
to aquatic ecosystems—and the once-mighty salmon now serves as its poster
child. In this chapter, we recount several of the events of the twentieth cen-
tury that led to massive reconi gurations of water in California and discuss
the impacts of water development on the state's environment. We use the
chinook, or king, salmon (
Oncorhynchus tschawytscha
)—a keystone species
whose decimation over the past century has been closely linked to water
development—to illustrate the ef ects of water development on aquatic
ecosystems in general.
the hydraulic era begins
During the westward push by pioneers in the early twentieth century, resi-
dents across much of the West experienced the region's unpredictable cli-
mate, with its periodic droughts and l oods, and set about taming the rivers.
h ey dug canals to water their crops, in some instances using ancient Native
American irrigation canals that had been preserved for centuries. As the
population grew, these attempts to control the water expanded, ultimately
leading to a total transformation of the natural hydrology of the region:
