As a child, Preston J. Arrow-weed lived near a stretch of the Colorado River that traced a wide, sweeping curve through the Fort Yuma-Quechan Reservation, which straddles the border of California and Arizona. The tribal elder recalls the way the river would swell during certain seasons, as rain or runoff upriver would send sediment-laden water coursing through the channel.

Last month, federal officials sounded the alarm by declaring the first-ever water shortage in the basin. The U.S. Bureau of Reclamation cited “historic drought,” climate change, and low levels of runoff from the Rocky Mountains as reasons for the continued decline of Lake Mead, the massive reservoir near Las Vegas held back by the Hoover Dam. Lake Mead’s stores are used by millions of people in the lower half of the basin, while serving as a critical safeguard against drought-related shortages.

Indigenous nations have recognized rights to more than one-fifth of the basin’s annual supply — more than a trillion gallons, or nearly enough to cover an area the size of Connecticut in a foot of water. That allocation is likely to increase in the future, because 12 of the tribes in the Colorado River Basin are still engaged in the decades-long process of resolving their water rights claims, according to the Water & Tribes Initiative, a coalition of tribal representatives, water rights attorneys and academics.

But even for tribes that have resolved their rights, some face significant barriers to fully using their water, including a lack of necessary infrastructure, funding challenges, and limited legal options to put their water to use outside their reservations through leases or other arrangements.

If a tribe does not (or cannot) use all the water it is entitled to, it doesn’t go unused; thirsty cities and agricultural fields downstream from reservations siphon off the surplus, but with no compensation for the tribe.

“The basin is free-riding off of undeveloped tribal water rights,” said Jay Weiner, an attorney for the Quechan Indian Tribe. Weiner said there is a “fundamental tension” between tribes’ desire to fully develop their water rights and the overarching need for everyone in the basin to consume less water overall.

Read the full article about Indigenous water rights by Mark Armao at Grist.