California reservoirs continue to struggle

The southwestern portion of the country has been suffering from a 22-year drought. It’s been so dry in this region that the U.S. government declared a water shortage along the Colorado River and Lake Mead in August of 2021. The Colorado River feeds into Lake Mead and the flows from the river have been reduced at least 20% since the beginning of this century.

NASA has been taking satellite images of Lake Mead and the they are showing the dramatic loss in water thanks to the extended drought pattern. This is the largest reservoir in the U.S. and it’s now at its lowest level since 1937, which was the year when the reservoir was being completed and filled. According to the U.S. Bureau of Reclamation, Lake Mead is now at only 27% of capacity. The reservoir supplies water to well over 20 million people across California, Arizona, Nevada and northern Mexico. Approximately 90% of the water from the Colorado River is relied upon by the residents of Las Vegas. It’s over 80% for many communities in the desert regions of Arizona and over 60% for Southern California residents.

In addition for drinking water and irrigation to farmlands, Lake Mead also serves as a recreation area for boating. The National Park Service now states that five of the six boating launch areas are now closed due to very low water levels.

As of last month, Lake Mead was at 1043.02 feet. During maximum capacity, the water elevation would be around 1,220 feet and, according to NASA, would hold around 9.3 trillion gallons of water. The only other occasions when Lake Mead was at full capacity were in 1983 and 1999.

As a result from the excessive dryness, the states of Arizona, Nevada, California and places into Mexico will see additional reduced water deliveries this year and into 2023, as the elevation of Lake Mead is expected to continue to drop below record-low levels. Lake Powell, the second-largest reservoir of the Colorado River, has also dropped to near 27% of capacity. The farming communities will be the ones that will likely experience the biggest cuts of water. Many fields are now likely to go unplanted because there will not be enough water to sustain the crops.

Here in the Inland Northwest, reservoir levels are close to normal. At Cliff’s station in northwestern Coeur d’Alene, we’ve had about 10 inches more moisture to date when compared to a year ago.

According to a study from Columbia University and published in Science Advances, the western U.S. has experienced one of its driest 20-year-plus periods in approximately 1,000 years. Despite a few wet years, the southwestern regions may be in the midst of another “megadrought,” which, according to tree ring data, can last for decades. Since 800 A.D., evidence shows there have been four previous megadroughts. They occurred in the late 800s, the mid-1100s, the 1200s and the late 1500s.

Researchers compared soil moisture records calculated since 2000 and concluded that the current drought is “already outdoing the three earliest ones.” The worst megadrought in the West likely occurred from 1575 to 1603. The article also states that the ancient droughts went on at least for several decades, but the one in the 1200s lasted for nearly a century.

For the best chance of above normal rainfall in the Southwest, we usually need to see a moderate to strong El Nino, the warmer than normal sea-surface temperature event in the waters of the south-central Pacific Ocean. Right now, ocean waters along the Equatorial region are still cooler than normal with the possibility of La Nina reforming or gaining strength later this fall. Although, the chances of a La Nina pattern through the rest of this year are higher, there are a few forecast computer models that are suggesting that a new El Nino may form sometime next year.

In terms of our local weather, it’s going to be hot later this week as high temperatures in Coeur d’Alene and surrounding regions will be climbing well into the 90s. It’s very possible that we’ll have a 100-degree day by late in the week.

It does look like we’ll end up slightly below the July precipitation normal of 0.92 inches in Coeur d’Alene, despite Cliff reporting eight thunderstorms this month. The average number of thunderstorms in July is two and the normal number of days with thunder, lightning and rain each year in Coeur d’Alene is 14.

There is the chance of more showers and thunderstorms in early August before another round of heat arrives in the region. By late August or September, we may start to see an increase in rainfall as the upcoming fall season is expected to be wetter than average. Of course, some of this will depend on the cooling of ocean waters in the south-central Pacific Ocean.

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Contact Randy Mann at randy@longrangeweather.com.