AILSA CHANG, HOST:
Here in Los Angeles, the rain has felt relentless. It's basically all anyone can talk about right now, which is so strange in a place that's usually obsessed with drought. What's been confusing the last couple weeks is we're a state that has been struggling with flood emergencies during a drought emergency. And while we're hearing a lot of talk about how these historic rainstorms have made a noticeable dent in the drought conditions around here, one question now is, well, how much further do we actually have to go to end the drought that has gripped parts of California and the West for years? We're going to get a reality check on that now with Sarah Porter, who directs the Kyl Center for Water Policy at Arizona State University. Welcome.
SARAH PORTER: Good to be here with you.
CHANG: Good to have you. OK. So can you just start us off as concretely as possible - is a drought defined by how much rain is falling, how much water is available to people in reservoirs, something else? What is the definition of a drought?
PORTER: Well, a drought really means below-average precipitation over some period of time.
CHANG: OK. So then what is the working definition of when a drought is over? Is it mostly about how much water is in the reservoirs?
PORTER: Yeah. As far as our Western water challenges go, it's not how much rain fell on the ground outside your door in Los Angeles or outside my door in Phoenix. It's how much snowpack has built up that supplies the big reservoirs. Something like two-thirds of Californians rely in part on snowpack in the Sierra Nevadas. In the larger Colorado River watershed, which includes seven states and Mexico, a vast region, most of the water that flows in the Colorado into the reservoirs that people rely on comes from snowpack in the upper Rockies. So we look at snowpack in those places to think about, how is precipitation impacting the water supply? And I would say we're in a good place in both the upper Rockies and in the Sierra Nevadas right now today. But we need that above-average snow to continue through the winter.
CHANG: Well, if we are talking about the Western region of the U.S., the areas that have seen ongoing drought conditions for, like, more than 20 years, how far away are we from this goal post that you have laid out that is full reservoirs? Can you just give us a real-world picture?
PORTER: First of all, there's so many variables, it's very hard to say generally. But let's just say generally, we're a few years away, especially to restore the Colorado River, which is such a critical water supply for Southern California and other big cities in the Southwest. We would need multiple years of well-above-average snowpack in the upper Rockies. The California water project that relies on water from the Sierra Nevada doesn't have as long a timeline to recover. But it - we would still need a couple really good winters for those reservoirs to start to recover.
CHANG: I guess I'm sort of listening to you, and I'm thinking to myself, well, no duh. A ton of rain and a ton of snow would be great for drought conditions. But meteorologically speaking, how realistic is it that we will actually see consistently this kind of historic level of rainfall and snowfall in the next several years consecutively?
PORTER: Not likely. The West is used to great variability. So we typically have a really wet year and then a string of dry years. With climate change, we don't know. And one other really important point, and that is that the hotter temperatures during the year mean that less of that snowpack turns into water that eventually makes its way into our river. The ground is hot and dry, so the ground holds more snowmelt, and more snow evaporates into the air than before. So the efficiency of turning snow into water that becomes the water supply in our reservoirs is really changing. And it's very difficult to predict what the trends will be in the coming years.
CHANG: Sarah Porter is director of the Kyl Center for Water Policy at Arizona State University. Thank you very much.
PORTER: Thanks for having me. Transcript provided by NPR, Copyright NPR.
