The biggest drought in 70 years, with rainfall at around a third of its normal level, has drained the Willamette river that feeds 13 reservoirs in Western Oregon, US.

The reservoirs, which have been left 35% emptier than they should be, are an important tourist attraction in the area and provide a venue for water sports. It is unlikely that they will be usable this year.

Eight of the dams in the scheme are multipurpose, providing flood control in the winter and generating 400MW of electricity, which is fed into the local grid. They are raised in the spring for summer recreation.The reservoirs, built between 1941 and 1980, are operated by the US Army Corps of Engineers. For two months in the winter they are left empty. In February the valves are tightened again to refill the reservoirs so that they are full by the beginning of summer when they will be used for sailing and other water sports. But this year forecasts suggest that the reservoirs will not be full by the start of the summer unless there is a spell of torrential rain: unlikely after March according to meteorologists.

Meanwhile, federal Endangered Species Act rules, designed to ensure that the Willamette river and its tributaries have enough water for the migration of salmon and steerhead, mean that water must be released from the reservoirs this spring. The Corps is still negotiating the size of this spring’s releases with the National Marine Fisheries Service, the federal agency in charge of restoring salmon populations. The head of Bonneville Power Administration (BPA) has said that emergency measures, such as holding back the releases for salmon and steelhead will be needed to ensure that the northwest has enough water to generate power. The fisheries service has also called for fishpasses to be operated on the scheme’s eight hydro dams, a measure that could reduce generating capacity further.

“The scheme produces 2% of the power used in the region, which covers three and a half states,” said Matt Rabe of the Army Corps. “And we will continue to generate power until the reservoirs are empty. But I doubt that the reservoirs will be high enough to use for sport.”

  Rabe says that the scheme becomes almost unmanageable in a dry year. “We have very limited options in operating these reservoirs because we have very specific conditions. They absolutely have to be empty all winter because downstream flooding would put life and property at risk, so we cannot begin filling them until January 15 every year.”

Rabe points out that it is not just the salmon that rely on the management of water level in the valley. Several industrial companies discharge waste into the river downstream from the reservoirs when water is released from the reservoirs in the fall. “The water we release dilutes the waste as much as possible, so we’ve also got the State Department of the Environmental Quality concerned about the levels,” he adds.

The two sides will have to come to an agreement as to what the releases will be by 29 March.