A canal carries water to Yakima River basin farmers. Irrigators with junior water-rights can expect only 48% of their full water allotments, the U.S. Bureau of Reclamation said May 16. (Don Jenkins/ Capital Press)

The U.S. Bureau of Reclamation projected Yakima River basin irrigators with junior water-rights will receive only 48% of their normal allotments, as a drought in Central Washington deepens.

The reclamation bureau issued a special mid-month water supply forecast May 16. Just 11 days earlier, the bureau had forecast irrigators would receive 51% of their full allotments.

A dry start to May has worsened the outlook. The bureau expects to begin rationing water within the next 10 days. Rationing starts when reservoirs peak and start dropping.

The bureau will issue another projection in early June. Depending on the weather, the water supply could rise as high as 65% of normal, but could drop to as low as 31% of normal, the bureau predicts.

Central Washington will be warmer and drier in June, July and August, according to a forecast issued May 15 by the federal Climate Prediction Center. The forecast was based primarily on a trend toward hotter and drier summers over the past 10 years.

Roza Irrigation District policy director Sage Park said the district anticipates rationing to begin early next week. The district will shut down its canal for seven to 13 days to conserve water for hot days and to extend water deliveries to the end of September, she said.

The timing of the shutdown will depend on whether the region gets rain soon, she said.

“The systems that are supposed to come in have either moved to the north or to the south. We’ll see what happens over the weekend,” she said.

The 72,000-acre Roza is the largest irrigation district impacted by water rationing. Roza has leased about 9,000 acre feet of water in preparation of the drought, Park said.

The reclamation bureau manages five reservoirs that provide water to irrigate some 464,000 acres. Irrigators with senior water-rights will receive full allotments. This will be the third straight summer in which junior water-right holders have been cut back because of a water shortage.

The reservoirs were low after last year’s irrigation season and never recovered. The reservoirs hold 75% as much water as usual. A La Nina failed to pack the wallop of past La Ninas. The Naches basin snowpack is 62% of normal, while the Upper Yakima basin snowpack is 40% of average.

Yakima River basin irrigators with junior water-rights received 52% of their normal supply of water last year. During a severe drought in 2015, irrigators received 47% of normal allotments.