My recent trip to the West got me thinking about the significance of water to society and the blessings we in this area have in that regard. News about the drought in the Colorado River basin and the recent agreement between California, Arizona, and Nevada to reduce their removal of water from the Colorado River highlights this significance.
I can recall my surprise when I first learned that the western states and Mexico actually harvested every drop of water from the Colorado, and that the river no longer reached the ocean in the Gulf of California. A 1944 treaty committed the United States to provide 1,500,000 acre feet of water to Mexico; all that water is currently diverted to the Mexicali Valley, a rich agricultural region closely related to California’s Imperial Valley.
In 1878 John Wesley Powell noted that the boundary between the water-rich east and the parched west was at the 100th Meridian, a north-south line bisecting Texas, Kansas, Nebraska, and the Dakotas. East of it, annual precipitation is greater than twenty-five inches and increasing; west of it the precipitation drops to negligible in the Great American Desert. Powell advocated strict Federal control of development west of the Meridian, with great focus on watershed management.
Before we began to manage the Colorado River, it averaged 16.3 million acre-feet of discharge into the Gulf of California per year, a rate of 22,500 cubic feet per second (cfs). Typical summer peaks were 100,000 cfs and winter lows 2,500 cfs. All-time extremes were 384,000 cfs in 1884 and 422 cfs in 1935. The construction of major dams – Hoover, Glen Canyon, and Parker – was justified by the desire to stockpile water and provide a dependable supply throughout the year.
To provide a perspective, the Allegheny River today averages about 19,750 cfs. The Allegheny drains a watershed of 11,580 square miles with an average annual rainfall of about forty inches. By comparison, the Colorado’s watershed is 246,000 square miles with an annual precipitation of perhaps twenty inches. It is estimated that eighty five percent of the annual flow in the Colorado is from snowmelt in the late Spring of the year.
Prior to this year’s changes, the 14.8 million acre-feet of Colorado River water allotted to our states included 4.4 million to California, 3.88 million to Colorado, 2.8 million to Arizona, 1.72 million to Utah, 1.05 million to Wyoming, 0.84 to New Mexico, and 0.3 million to Nevada. California’s allotment goes primarily to the Imperial Valley. Before management, the Imperial Valley was part of the Sonoran Desert, mostly below sea level. Irrigation canals from the Colorado converted it into a rich agricultural region (500,000 acres) that today is a major producer of sweet corn, sugar beets, and alfalfa. In addition, a significant amount of water (perhaps 1.4 million acre-feet) is transported to Southern California to partially serve 19 million customers in the San Diego/Los Angeles area.
On an annual basis one acre-foot of water is required to provide “city water” for nine persons. For agriculture, four acre-feet per year is typically required to irrigate one acre of farmland. The Imperial Valley is an exception, of course. Its requirement of six acre-feet per year is a direct consequence of the fact that it has a twelve-months growing period; in reality, it is the nation’s most productive county for the production of winter vegetables. What is water worth? The Federal government has agreed to reimburse the three Lower Basin states $1,200,000,000 for a usage reduction of 300,000,000 acre-feet in the next three years; this equates to one quarter of a cent per gallon. Currently the Imperial Valley farmers pay the irrigation district about a third of a cent per gallon
Although Lake Mead and Lake Powell receive most of the publicity, there are thirteen other dams and reservoirs on the main Colorado River; an additional twenty on tributaries in the Upper Basin (upstream from Lee’s Ferry, Arizona), and eleven in the Lower Basin. Oldest of these is the Theodore Roosevelt Dam and Reservoir, constructed in 1911 on the Salt River to provide hydroelectric power and potable water to the Phoenix area at a time when the population there was less than 20,000 (today the Phoenix metropolitan area has a population of four and a half million). Hoover Dam and Glen Canyon Dam today hold back fifty-five million acre-feet of water; storage behind the other forty-three dams amounts to an additional twenty-one million acre-feet. Hoover and Glen Canyon generate 3.3 megawatts of hydroelectric power; the other dams, about 1.2 megawatts.
In 1952 the U. S. Supreme Court resolved a dispute between Arizona and California, establishing the current allocations of Colorado River water. At that time the total demand each year was about eight million acre-feet, far smaller than the 16.3 million allocated. In 1952 the population of the United States was about one hundred fifty-two million, less than half what it is today. In the ensuing years demand has increased sufficiently that each of the allocations is fully harvested.
My current opinion about this problem is that the recent drought and the possibility that it has been aggravated by climate change is not the root problem. As our population has continued to grow, the associated increase in demand for fresh water in the Colorado Basin and Southern California has increased linearly to the point where it now matches the average output of the river. Perhaps we have reached a Malthusian point where population now exceeds a critical resource.
All of which highlights the responsibility we in this area have to be better stewards of our streams. Let’s build on the success of the abandoned mine drainage facilities at Wingfield Pines and on Millers Run and finish the job of restoring Chartiers Creek. Let’s clean up Coal Pit Run, McLaughlin Run, Painters Run, Scrubgrass Run, etc. It is a small price to pay for the blessing we have of ample annual rainfall.