The Supreme Court on Monday kept in place environmental orders in California that protect the endangered delta smelt and limit the pumping of river water from the Sacramento-San Joaquin Delta.
The justices turned down appeals from several water agencies, including the Metropolitan Water District of Southern California, and from Central Valley farmers.
In their appeal, the water agencies questioned whether limits on pumping water to the southern part of the state were required under the Endangered Species Act and said the restrictions were particularly harmful to consumers, farmers and other water users during the drought.
The court's action is a victory for environmentalists. It has the effect of upholding a decision of the 9th Circuit Court of Appeals.
In a 2-1 decision, 9th Circuit judges said federal wildlife officials had a duty to take "reasonable and prudent" measures to protect the 3-inch-long delta smelt, regardless of the cost to the economy.
The Supreme Court upheld this view of the Endangered Species Act in the 1970s case of the endangered snail darter, and the justices have shown no interest in revisiting the issue.
In addition to protecting the tiny smelt, the 9th Circuit has also upheld limits on pumping to protect several species of salmon which migrate through the San Francisco Bay and the delta.