Federal officials on Friday sharply cut how much water Arizona, California and Nevada can draw from the Colorado River over the next two years in an attempt to stabilize a system on the verge of collapse because of climate change and overuse.

The existing rules governing use of the river and of the nation’s largest reservoirs, Lakes Powell and Mead, were set to expire this year, just as drought constricts the Colorado’s flow and both lakes shrink to record lows. Friday’s announcement by the U.S. Bureau of Reclamation reduced the allocation for the three states by about a quarter, in total, reducing Arizona’s share by the most, about a third.

The plan formalized voluntary cuts the states had already offered to accept and settles months of uncertainty over how the water supply will be managed in the coming years. But it does little to solve the underlying crisis: The river’s flow is diminishing and reservoirs are drying up, but communities and farms still use unsustainable amounts of water.

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