Water Supply Concerns As Drought Persists In Western U.S.

There was "minor improvement" in California drought conditions over the past week. But as long-term drought persists throughout the west, and storage levels drop, water supply concerns rise.

The dry summer months are ahead and it’s less likely that there will be any dramatic improvement in the level of drought, or drought intensity, in California.

The Drought Center measures the intensity of drought. The only change in California (as of the report’s Tuesday morning cutoff) is a 2.5 percent reduction in the level of severe drought in northeastern California.

The area of California where drought has been removed, roughly 10 percent, stretches from the northwest coast to the northeast, along the Oregon border.

"Improvements were made in an area of Severe Drought (D2) in northeastern California and northern Nevada where overall conditions have continued to steadily improve during the past year," the U.S. Drought Monitor reports May 26. "According to the NOAA NCEI Climatological Rankings, Nevada Climate Division 1 (Northwestern Nevada) experienced its 9th wettest 12-month period (May 2015-April 2016) on record."

Conditions improved in Nevada, as the level of severe drought was reduced 8 percent from the previous week to 28 percent.

This week, federal water managers reported that Lake Mead, which provides water from the Colorado River to California, Nevada, Arizona, and four other states, reached its lowest point since 1935.

"Coming into the summer months, Lake Mead currently sits at 37 percent full while Lake Powell is slightly higher at 48 percent full, according to the May 23 U.S. Bureau of Reclamation Lower Colorado Water Supply Report," the Drought Center reports.

The latest reservoir update from the California Department of Water Resources shows that Lake Oroville is at 112 percent of its historical average, while Lake Shasta is at 107 percent and Folsom Lake is 104 percent.

As of May 25, the statewide Sierra Nevada snowpack is 29 percent of average for the 96 reporting stations in the southern, central and northern Sierra.

Along with northeastern California and northern Nevada, other areas of the western U.S. saw minor improvements in drought conditions, including northwestern New Mexico and southeastern Alaska.

"But in the Northeast, Northwest, and Southeast, short-term precipitation deficits, low streamflows, and pockets of dry soils led to further deterioration of conditions," the report notes. "In northwestern Oregon, short-term dryness and degraded streamflow conditions led to the expansion of areas of Abnormally Dry (D0)."

Looking ahead, the 6–10 day outlooks call for a "high probability of above normal temperatures in the eastern half of the U.S. and Far West while below normal temperatures are expected in the Desert Southwest, extending northward into the eastern Great Basin and Central Rockies. Below normal precipitation is forecasted for the Pacific Northwest, much of California."