Last week Arizona and California missed a deadline to submit final plans for how they will manage water shortages in the Colorado River Basin over the coming decades to prevent Lake Mead levels from dropping so low that water cannot be released from the dam. The other five states that share the river’s waters have already submitted their drought contingency plans. We talked to John Fleck—director of the University of New Mexico’s Water Resources Program and a member of the PPIC Water Policy Center research network—about the situation.

PPIC: What is the drought contingency plan intended to do?

John Fleck: The key problem on the Colorado is that the basin’s water is over-allocated. It was really wet in 1920 when the allocation rules for the river were developed. So the rules allocated extremely large water shares to the “lower basin states”—California, Arizona, and Nevada—that hydrologic reality can’t support. We’ve been struggling ever since to come to terms with that reality.

The drought contingency plan is a voluntary program involving the lower basin states to decrease their use of the river’s water in an attempt to reduce the over-allocation problem. There’s an overall agreement describing the conditions that would require each state to use less water. Then each state has to have its own separate internal set of agreements on how to share those cuts.

There are a couple of different ways you can approach this over-allocation problem. The federal government can just reduce everyone’s allocation. Or you can have the water users themselves acknowledge the problem and agree to a voluntary, collaborative approach. The latter approach is far more likely to succeed, so I definitely think this was the better way to go.

Even though the lower basin states are close to having final plans, federal officials have said that “close isn’t done.” The states now have until March 4 to submit their final plans. No one wants to have an imposed federal solution—and I don’t think we’ll end up there—but it’d be better than doing nothing. The threat alone might push people to finish up.

PPIC: What are some important steps the states have agreed to?

JF: The agreements reduce water use in the lower basin by 1.5 million acre-feet per year; it’s a very big deal. Arizona has now agreed to a plan that could eventually reduce the Central Arizona Project’s flow of Colorado River water into the valleys of Tucson and Phoenix by nearly half of current levels. They did this voluntarily, without any litigation. That’s real progress. And Imperial Irrigation District (IID)—the biggest agricultural user of California’s allocation of Colorado River water—has already given up 500,000 acre-feet a year, which is a huge amount of water.

One of the complications of reductions in Colorado River water is the drying of the Salton Sea, which relies principally on runoff from farms in IID. California promised to mitigate the public health and environmental problems associated with the shrinking of the sea, particularly the air quality impact on poor communities. Solving this problem is a work in progress made more challenging by reductions in Colorado River water.

PPIC: Do you think the states’ plans go far enough, given the warming climate?

JF: We can’t be sure, because we don’t know how much impact climate change will have, on what time scales. Since we don’t really know where the bottom is for the Colorado River, hydrologically speaking, we don’t how far we’re going to have to go with water cutbacks in the long run. Drought planning is a really important step to prepare for a climate-challenged future—it creates a framework for deeper cuts.

It’s important to see the drought contingency planning as the latest development in the evolution of long-term management of the river’s waters. There are a bunch of unresolved problems—both hydrologic and institutional―and a lot of work remains to be done, but we can’t solve all these problems at once. Though drought planning is an incredibly important step, it’s certainly not the last one.

Fleck is a co-author (with Eric Kuhn) of the upcoming book Science Be Dammed: How Ignoring Inconvenient Science Drained the Colorado River, to be published this fall by the University of Arizona Press.