The drought has dried up water supplies in some parts of the country — and water wars are heating up, between farmers and other industries and cities. In New Mexico, farmers have kicked off what could be a long-running fight by making a “priority call” on water resources. 

What exactly does that mean? Put simply, water rights in the Western states are “first come, first served.”

“The idea is that the people who were using the water first, they get the first call on the water that there is,” explains Holly Doremus, an environmental law professor at UC Berkeley.

Making a “priority call” says I was here first and I want my water.

“It’s the mechanism to allocate water during times of shortage,” says Ronald Kaiser, a water rights expert at Texas A&M University. “There’s no share and share alike, there’s no reasonable use.  The allocation of water is based on first in time, first in right.”

There is a problem with these rules — they’re old. In lots of cases, they promise water to famers before cities. For that reason, Kaiser guesses they’re going to change.

“I think what’s going to happen is that the legislature will not let cities go dry,” he says, but he thinks it will be tension filled, politically and legally.