A water war is looming between Mexico and the US. Neither side will win | CNN

Under an 80-year-old treaty, the United States and Mexico share water from the Colorado River and the Rio Grande .

But in the grip of severe drought and searing temperatures, Mexico has fallen far behind in deliveries.

Some Texas leaders have called on the Biden administration to withhold aid from Mexico until it makes good on the shortfall.

The Rio Grande — called the Río Bravo in Mexico — is one of North America’s longest rivers.

The water from Mexico goes to the Falcon and Amistad Reservoirs which straddle the border and provide water to homes and farms.

Low water deliveries from Mexico , combined with a dearth of rain in the region, are threatening the state’s citrus industry.

Mexico is enduring its most expansive and severe drought since 2011 , affecting nearly 90% of the country.

Some hopes lie in a tropical storm or active hurricane season.

To rely only on storms to reduce water scarcity would make Mexico “totally exposed to what nature decides about our water future,” UNAM ’s Magnaña Rueda says.

Water sharing agreements must adapt to a changing climate, she says.