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Here's how water moves through Lake Powell

 Wake from a boat on Lake Powell with a red mesa in the background
Zach Tilford

The Colorado River plays a pivotal role in the lives of many western state residents as a major municipal and agricultural water source. Lake Powell, a reservoir on the border of Utah and Arizona, is fed by the Colorado River. Water then flows from Lake Powell into the Grand Canyon and Lake Mead downstream.

While the Colorado Rockies did not get quite the snow year seen in Utah, Colorado did see above-average snowpack. This year's projections of water flow into Lake Powell are nearing the 21st century record high flows of 2011.

Lake Powell is a reservoir, unlike Great Salt Lakewhich is terminal, so snowpack and water flow into Lake Powell greatly impact numerous communities downstream.

Jack Schmidt is a natural resources professor and Janet Quinney Lawson chair in Colorado River Studies at Utah State University. Schmidt has spent his career focused on the Colorado River system.

“Lake Powell is a reservoir; it's not a lake. And, like any reservoir, it has a drain,” he said.

This is an important difference, as it is going to respond much differently to increased spring runoff.

The elevation of Lake Powell is determined not only by how much water is flowing in but also by what is released for downstream use. This water is essential for Arizona, Nevada, southern California and Mexico, so a lot of water gets discharged. As many people rely on the Colorado River, both before and after it reaches Lake Powell, it is highly regulated by an array of agreements, court rulings and laws that span multiple states.

“The law of the river, as it now stands in this complicated array of agreements, is that the contents of Lake Mead and Lake Powell can be kept approximately equal in their contents,” Schmidt explained.

So, regardless of inflow, Lake Powell releases enough water to keep Lake Mead in Nevada at a similar water level.

Once water flows through the Grand Canyon and into Lake Mead, it moves downstream through Arizona where some is used, and the remainder is diverted to California. Anything left over is used to water farm fields in Mexico. Historically, the Colorado River flowed into the Gulf of California, but now, none makes it to the ocean, even in wet years.

“We have been overspending or using more water than comes in for 22 years. And we drain the system to almost nothing,” Schmidt remarked.

Given current water levels and past drought years, several years of increased water runoff are needed to restore water stored in Lake Powell, if usage continues at its current rate.

“The only way to make the most of this and the only way to significantly rebuild storage is to significantly cut use in the same year that you're having a big water year,” said Schmidt.

According to Schmidt, even though there are major increases in water runoff this year, it is unlikely to significantly impact future water availability in the West without current water conservation measures.

Just last week Arizona, Nevada and California agreed to a federal conservation proposal that will decrease water use through 2026, conserving a minimum of 3 million acre-feet of water. Part of this will come from federal government compensation, and the rest through voluntary reduction by those states.

Read the first part of this story on the Colorado River here.

Erin Lewis is a science reporter at Utah Public Radio and a PhD Candidate in the biology department at Utah State University. She is passionate about fostering curiosity and communicating science to the public. At USU she studies how anthropogenic disturbances are impacting wildlife, particularly the effects of tourism-induced dietary shifts in endangered Bahamian Rock Iguana populations. In her free time she enjoys reading, painting and getting outside with her dog, Hazel.