By Deana Ikeya and Chuck Cullom, CAP Colorado River Programs
We live in the desert, but we keep an eye on the snow in the Rocky Mountains. That’s because CAP’s source of water is the Colorado River and more than 90 percent of the river’s flow originates as snow in the Rocky Mountains of Colorado, Wyoming and Utah.
The 2016/17 winter has brought exceptional snowfall to the Upper Colorado River Basin. We are nearly at the peak of the season now and are seeing snowpack at about 137 percent of the average from 1981-2010. Soon we will move into the runoff season as the snowpack begins to melt and the runoff will fill the rivers and reservoirs in the Upper Basin, eventually making its way into Lake Powell. Lake Powell and Lake Mead are the two largest reservoirs on the Colorado River system and operated conjunctively. The amount of water released from Lake Powell to flow to Lake Mead is determined by in part by the elevation of each lake and the amount of runoff.
The amount of runoff coming into Lake Powell is estimated by the National Weather Service through the Colorado Basin River Forecast Center. This runoff estimate will determine how much water will be released from Lake Powell. The current estimate for the runoff season is projected to be 10.4 million acre-feet (MAF). If this projection holds, this year would be the 9th largest runoff in the last 36 years.
Based on the projected runoff that flows into Lake Powell, the Bureau of Reclamation will make a determination in April on the amount of water to be released from Lake Powell into Lake Mead to supply water to the Lower Colorado River Basin. There is a very high likelihood that Lake Powell will be operated to release 9.0 MAF, which is more than the normal release of 8.23 MAF. In fact, there is a slight chance that the projected runoff could be high enough to push Lake Powell’s operations to release more than 9.0 MAF. Regardless, these higher volumes of water in Lake Powell from the increased runoff, along with ongoing conservation programs, will help to keep Lake Mead out of shortage in 2018 and likely for a few years beyond that.
California has also received a tremendous amount of rain and snow this winter, enough to bring most of that state out of its severe drought conditions and to nearly fill most of the state’s reservoirs. While this water won’t directly contribute to the Colorado River system, it will reduce California’s use of Colorado River water allowing more water to be stored in Lake Mead, further reducing the risk of shortage conditions in the near term.
While it looks like all of this rain and snow has been good news for Colorado River water supplies, it is important to remember conditions could change. A warm, dry spring could reduce the projected amounts of runoff and increase water demands. Also, a low runoff year in the near future could diminish or erase these potential gains. CAP continues to track the current conditions and projections. You can read our monthly updates.