Winter snow not adding up for good water year in West - Tucson News Now

Winter snow not adding up for good water year in West

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Source: Stewart Tomlinson, USGS Source: Stewart Tomlinson, USGS

The Colorado River is by far the most important surface water resource in the western United States. Seven states receive Colorado River water. These are Arizona, Nevada, California, New Mexico, Utah, Colorado, and Wyoming. Each of the states claim a part of the Colorado River Basin. 

The two largest water reservoirs on the Colorado River are Lake Powell and Lake Mead. These lakes are filled mainly with spring snow melt from higher elevations. This year the numbers are not looking good.

From October through February, the average precipitation for the Colorado River Basin as a whole was dry. Look at the image below. Reds, oranges, and yellows show below average precipitation. Those colors cover much more area than the blues and greens, which indicate average or above-average precipitation. (Note that Southeast Arizona is especially dry.)

What does the below-average precipitation mean? It basically means the long-term drought continues across much of the western U.S. And it means another year where lake levels in the reservoirs may drop to lows that cause some concern with officials.

While the West won't run out of water, we are using water from the Colorado at a rate that is not sustainable over the long term. Just like you can overdraw on your bank account, the allotments for the Colorado River water are overdrawn compared to the long-term average.

How did this happen? The Colorado River water was divvied up with only a decade worth of river flow observations. These observations were recorded during an unusually wet period in the West. Looking at more current numbers that stretch across centuries, the Colorado River simply does not sustain the wet flow seen in that decade worth of observations on a regular basis. This means, at some point, a drastic change may be needed to keep water resources stable for all user states that share the Colorado River water. 

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