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 in use 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 steelhead, 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 eme- rgency 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.