Earth Day: Population Growth in Desert Southwest Will Tax Water System

(April 22) -- On Earth Day, it's fitting to talk about one of the -- if not the -- most pressing political, social and ecological problem for California and the Desert Southwest in the coming years: a lack of fresh water. The population will continue to grow, and the climate -- regardless of any potential influence of global warming -- will be arid and inconsistent.

It's not that water problems are new to this region, of course. Water battles have raged for decades, including political battles regarding communities getting enough water to satisfy large populations.

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There have also been battles related to the billions of annual agricultural dollars in a region that is home to the largest agricultural state in the nation (California), and ecological battles related to wildlife and natural areas contained within an ecosystem that is delicately balanced in a dry climate.

It's just that the problems are destined to get worse -- potentially much worse.

From 2000 to 2008, Arizona's population increased by 26.7 percent and Nevada's population increased by 30.1 percent, according to the U.S. Census Bureau. California is growing at a slightly higher rate than the national average. By 2025, it's projected that these three states will be home to a combined 61 million people, compared to 43 million in 2010.

The annual U.S. precipitation map shows that this large population increase is occurring in a region where less rain falls than anywhere else in the country, with much of Nevada, Arizona and Southern California receiving an average of less than 10 inches per year on average.

(Image courtesy of Western Region Climate Center)

Granted, precipitation amounts are much more significant in Northern California and in the mountains, including the Sierra and the Rockies. This rain and the melted mountain snow are important to fulfilling the needs of fresh water. Parts of the region also use groundwater fed by underwater reservoirs. This so-called fossil water, though, is analogous to fossil fuels in the sense that it is naturally limited.

In a year when above-normal precipitation occurs in southern areas, these water sources in combination with the precipitation can meet the water needs of the region. However, the inconsistency with which the winter precipitation comes often results in a year with water scarcity or, worse, a series of years with water scarcity.

That's the nature of the weather in California and the Desert Southwest.

Pacific storms are abundant most years, but they often track to the north for multiple years in succession, leading to multiyear, growing droughts. This has always been a recurring theme for California. In fact, even though winter storms this year greatly alleviated drought conditions, some of the Desert Southwest and California is headed toward its fourth year of drought. Multiyear droughts date back to the 1820s.

Imagine the impact of a three-year, four-year or even a five-year drought when 18 million additional people need water, and additional water will be needed for the agriculture production increases associated with a growing national population. It's inevitable.

With the water systems of today already a complex patchwork of dams, reservoirs, rivers and aqueducts, how will the future water needs be met?