WASHINGTON (AP) — A new study finds climate change could cut stream flows in the Potomac River basin, a major source of drinking water in the Washington region.

The study found by 2040 climate change could cut stream flows 35 percent. And a moderate drought combined with that worst-case scenario could mean mandatory water restrictions assuming changes are not made to the region’s water supply system.

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The study was conducted for the Interstate Commission on the Potomac River Basin, which is charged with conserving water resources of the Potomac and its tributaries. The commission notes more than three-quarters of the Washington region’s water supply is taken from the Potomac.

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The commission includes members from Maryland, Virginia, West Virginia and Pennsylvania as well as the federal government and the District of Columbia.

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