Thursday, February 22, 2007
Colorado River to Take Hit from Global Warming
Anyone who has paid close attention to water issues in the West will find much that's familiar in a new report from the National Research Council about the Colorado River. The report warns that increasing population growth in the interior West, combined with droughts made worse by global warming, will be putting increasing pressure on the Colorado.
The report notes that the Colorado River Compact, which divied up the flow between the upper and lower basin states, was signed in 1922 — right after a particularly wet period in the interior West. The average flow for the purposes of the compact was pegged at 16.4 million acre feet a year. Today, according to the report, the average flow of the river is 15 million acre feet per year. And tree-ring records show that extended droughts lasting decades or even longer are a recurrent feature of climate in the West, causing the Colorado's flow to fall significantly below average.
Now, based on many climate model simulations, "the preponderance of scientiﬁc evidence suggests that warmer future temperatures will reduce future Colorado River streamﬂow and water supplies," the report concludes. "Reduced streamﬂow would also contribute to increasing severity, frequency, and duration of future droughts."
This is occurring against the backdrop of a burgeoning population in the West. Arizona alone saw its population rise by 40 percent just since 1990. Here in Colorado, population grew by 30 percent. Although Westerners have made strides in reducing per capita water use, continued conservation will not be enough in the face of rising population and dropping availability of water, the report states.
It offers no simple solutions. Instead, it calls for continued conservation, use of innovative technology, greater cooperation between Colorado River basin states to prepare better for drought, increased communication between water managers and scientists, and, of course, more study:
"The report thus recommends a comprehensive, action-oriented study of Colorado River region urban water practices and changing patterns of demand be conducted. The study should evaluate a range of issues, including demographic projections and water demand forecasts, impacts of urban water demands on riparian ecology, and contemporary urban water policies and practices."
No surprises there, but the issues raised by the report are a reminder of the compelling need for good environmental journalism in the West. Reporters who are knowledgabe about the complexities of water in the West are desperately needed — to avoid common mistakes, such as the one made in NPR's All Things Considered broadcast on the report by Elizabeth Shogren yesterday. It wasn't a huge mistake, but it betrayed a lack of knowledge of how the reservoir system on the Colorado River works. Shogren stated that Lake Mead "keeps taps flowing in Southern California, Nevada, Arizona and Colorado. The problem is that Colorado gets no water from Lake Mead.
Lake Powell, impounded behind Glen Canyon Dam, is a kind of hydrological bank for the upper basin states — Colorado, New Mexico, Utah, and Wyoming. It helps the states meet their obligations under the Colorado River Compact to send a specified amount of water down the river to the lower basin states — Arizona, California and Nevada. When drought prevails, the upper basin states can take water out of the bank and send it downstream, meeting their compact obligations while also satisfying their own water demands. Meanwhile, Lake Mead is used by the lower basin states to store water for their own uses. According to the U.S. Bureau of Reclamation, "Hoover Dam helps ensure a dependable water supply for municipal, industrial and other domestic uses in southern Nevada, Arizona and southern California. More than 16 million people and numerous industries in these three states receive Colorado River water that was stored by Hoover Dam."
No taps in Colorado depend on water from Lake Mead.