As drought deepens in the West and the water used by farms and people alike dwindles, farmers in Arizona and California are bracing for cutbacks in the two major federal systems that supply irrigation and drinking water to millions of people.
Water storage is shrinking with no snowpack to replenish reservoirs managed by the Bureau of Reclamation in California and Arizona. Shasta Lake in northern California is about half full while lakes Mead and Powell, the two giant reservoirs designed to contain more than 50-million-acre feet of water behind Hoover and Glen Canyon dams, respectively, are precariously low with under 20-million-acre feet of total storage combined.
What ranged from normal to moderate drought conditions in the West a year ago has descend into exceptional drought conditions for much of the U.S. Southwest. Most of the Colorado River basin is in the exceptional category with lesser classifications on the Sacramento and San Joaquin rivers in California. Better hydrologic conditions are reported on the Columbia and Snake rivers in the Pacific Northwest and Idaho.
Arizona agriculture hit first
On the Colorado River system this means that Central Arizona Project (CAP) water users will lose 512,000-acre feet of the estimated 1.6-million-acre feet they can access in non-critical years, according to Ken Seasholes, manager of resource planning and analysis for the CAP. The restrictions are spelled out in a tiered system previously negotiated to manage water deliveries from the system during drought.
The CAP delivers water to agricultural, municipal, and tribal users in central Arizona.
Lake Mead elevations are the cornerstone of these reductions and is set up in eight tiers, based on surface elevation above sea level. Under negotiated water agreements, the CAP bears the brunt of reductions under the first three tiers with minimal reductions to Nevada's water allocation from the river. California, the largest user of Colorado River water, will face no reductions in allocation under the Tier 1 shortage.
Arizona farmers will be the first to lose as the CAP cuts their 300,000-acre-foot allocation, forcing them to rely on wells or fallow land.
The reduction to farms comes after the CAP was forced to reduce its draw on the Colorado River by 192,000-acre feet in 2020 as Lake Mead fell below the 1,090-foot threshold for Tier Zero restrictions. The CAP bears the brunt of early water delivery restrictions under the tiered system. California users of Colorado River water would not see reductions in allocations until Lake Mead reaches 1,045 feet in surface elevation.
CAP Spokesperson DeEtte Person said the agency will have more details on projected cutback and how individual districts in Arizona will be affected by early May.
Shasta Critical year
Similar water woes are being felt by California farmers under a Shasta Critical designation that paves the way for cuts to even the senior-most water rights holders.
This determination by the U.S. Bureau of Reclamation is a legal one, setting the stage for Reclamation to allocate 75% of their contractual obligations to senior water rights holders under the Sacramento River Settlement and San Joaquin River Exchange contracts. Under both contracts, Reclamation cannot reduce water deliveries to senior rights holders below 75% of their promised allocation.
Similarly, wildlife refuges are allocated 75% of their contract supplies. Municipal and industrial water users were initially promised 55% allocations. Central San Joaquin Water Conservation District and Stockton East Water District were each promised full allocations.
For growers south of the Delta in California, this means another year of zero water deliveries from the giant federal project.
The Shasta Critical decision is predicated on inflow projected to reach Shasta Lake. When that projection falls below 3.2-million-acre feet in any one water year, the Bureau of Reclamation will reduce its allocation of water promised under the federal contracts. Shasta Lake is the cornerstone reservoir in the Central Valley Project (CVP) and can store over 4.5-million-acre feet behind Shasta Dam. Total storage in the dam as of mid-April was just over two-million-acre feet, or about half of its designed capacity.
The news of water cutbacks by federal water managers was expected by CVP contractors.
In a prepared statement, Federico Barajas, executive director of the San Luis & Delta-Mendota Water Authority indicated his understanding of why such a low allocation was made.
"The San Luis & Delta-Mendota Water Authority understands that dry hydrology is the main driver in the low initial allocations for our member agencies and the communities they serve,” he said in his statement.
The allocation to Barajas' agency alone affects nearly 1.2 million acres of highly productive farmland and three million people in central California. This includes the highly populated Silicon Valley and sparsely populated regions that include economically poor communities along the west side of the San Joaquin Valley.
"The authority wishes that the initial allocation was higher but understands that existing conditions have prohibited Reclamation from making a higher initial allocation," the statement says.
The state's rice industry will likely be impacted, but just how much so remains to be seen. California rice farmers can plant about 500,000 acres to rice in California – much of this in the Sacramento Valley between Chico and Sacramento. Tim Johnson, president, and chief executive officer of the California Rice Commission said he will not know acreage estimates until late April or early May.
Though significant to rice farmers, the CVP is not the only source of irrigation water to the state's rice industry. Still, it is the only source of irrigation water for some rice farmers.
Friant Water Authority predicted the poor allocation will mean more groundwater pumping this summer, a common move among growers when surface irrigation supplies are lacking. This has led to ground subsidence, a phenomenon that has significantly strangled Friant's ability to deliver surface irrigation supplies along its 153-mile canal system.
Friant receives its water from Millerton Lake above Fresno, Calif. The first 800,000 acre-feet of available water is considered "Class 1" water. Districts with Class 1 contracts were told to expect 20% of their contracted supply. Additional water referred to as "Class 2" supply will not be available.
Because Millerton also feeds the San Joaquin River, some of that water is earmarked for the San Joaquin River Restoration Program. Under current hydrologic conditions, over 170,000-acre feet of Millerton Storage will go to those programs.
In its written statement following the USBR announcement, Friant Water Authority said: "We anticipate that many growers throughout the south San Joaquin Valley and on the Eastside will need to rely heavily on groundwater supplies, just as they did in 2020. This is likely to further exacerbate the type of regional land elevation subsidence that has so dramatically reduced the capacity of the Friant-Kern Canal and other valley canals. This makes our efforts to increase the availability of surface supplies to the San Joaquin Valley and to fix the Friant-Kern Canal’s capacity limitations even more critical and underscores the need for resolving the valley’s long-term water imbalance."