Colorado River Water Supply

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Central Arizona Project General Manager David Modeer talks about the Colorado River Basin Water Supply & Demand Study, a collaborative effort between the federal government and seven western states to assess the adequacy of Colorado River water now and in the future.

Ted Simons: A multiyear study is underway to determine future supply and demand needs for Colorado River water. Here to tell us more is David Modeer, general manager of the Central Arizona Project. Thanks for joining us. Let's just get to basics here. What are you looking at, and what so far are you finding?

David Modeer: We're looking at two different areas with the Colorado. One is to quantify, what is the current and future demands on the need for Colorado River water among the seven basin states. The second phase will be knowing what the demands are and what the potential supply in the river is in the future. What can we do to provide a sustainable supply or to augment the supply.

Ted Simons: And we mentioned it's a multiyear, multi-subject kind of a study.

David Modeer: This is the first phase, trying to quantify what are the demands on the river, municipal, agricultural, and industrial, today and into the future.

Ted Simons: What's the study showing so far?

Ted Simons: There's going to be increasing demands on the river. We've known for oh while that the supply on the river was less than ever anticipated to be when it was allocated in the 1920's. It's important to know your needs before you start determining what you can do to make certain those supplies stay consistent for the needs into the future.

Ted Simons: How do you figure out the variables? How do you slow down the moving target? How do you slow that target down?

Ted Simons: It is a moving target because you're looking at all aspects of water use. You're looking at growth in population. You're looking at the potential efficiencies that can be gained by increased levels of conservation. You have to make some estimation of what's going happen in order to quantify that supply. There is a bit of science involved, not just straight empirical measurements involved in getting to this point.

Ted Simons: I would assume climate change is part of that science?

David Modeer: Yes, climate change is part of that. The climate impact studies are not complete yet. The difficulty is we do have global climate change models but we have not been very good at down-scaling to a specific watershed like the Colorado River. What is the impact on supply? You may have natural periods of drought that could be layered on climate change. Those all play part in what is the supply, and how can that limited supply meet the demands in the future.

Ted Simons: You mentioned drought, obviously a big factor here in west. What can you tell us so far regarding a drought frequency or duration?

David Modeer: If you look back in history over the past 1500 years or so, you will see substantial periods of drought. We're talking periods of 40 years or so. Which will have a serious impact. We've been almost 13 years of drought now to this point in time this. Interspersed with a few wet years, this has been a very great year along the Colorado but the drought is not over. We know through tree ring studies and other scientific tests, the drought consist last for a long time and be of variable intensity.

Ted Simons: This seems to be like it would be a big variable when you have massive wildfires in certain areas of northern Arizona, where you're going to wind up with mudslides, flooding. The water that's supposed to go to X is now going to Y and it's not the best of water. How does that play into what you're looking at?

David Modeer: Forest fires have a significant impact on watersheds. Fires in Arizona don't impact the Colorado River watershed because they are not in that Pacific watershed. There have been fires on the upper Colorado with the same impact. You don't get any infiltration into the earth in first years after a fire because you pretty much almost fry the ground, so that the water is not able to penetrate into the soil. So your impacts are longer lasting, but you don't increase the water in the watershed and lessen the amount of supply that happens over a period of time when you do get rains.

Ted Simons: Sounds similar to snowpack and the concern that slow pack, which does allow water to seep in, may be replaced by rain, which doesn't necessarily go in.

David Modeer: Particularly a year like this on the Colorado, it's going to 16 be continuing to feed water into the watershed and the ground for months on end. Rain, if it's heavy and replacing snow that would normally happen, you get tremendous runoff in a very short period of time that creates flooding and is sometimes in certain watersheds very difficult to retain that supply.

Ted Simons: Ok, so you're looking at supply and demand, and possible imbalances here for the next 50 years or so. As far as the research, who's doing the research? And how is the research being done?

David Modeer: A number of universities are doing the research, and also NOAA, National Oceanic and Atmospheric Administration, Universities at Arizona, Universities in Colorado and consultants who are experts in analyzing the uses of water and analyzing the impacts of drought and climate change on it. So there's a very broad group of scientists and University types that are taking a look at the various aspects of demand and supply.

Ted Simons: Bottom line: What do we take of this particular snapshot?

David Modeer: Well, I think what we can take out of this is what we've known, that is the demand is outstripping the current supply along the Colorado and it'll probably get greater, that gap, in the future. Getting precise numbers as to what it may look like in the future is very important for us to be able to make decision on what we do to try to augment that shortage. Do we do things like desalination? Do we begin the transfer of agricultural water to urban usage? Increase the levels of conservation through other specific programs? There are a number of alternatives out there. To know which ones are the most economical to pursue, you need to know the supply and demand numbers in the future.

Ted Simons: Once we get a better indication of the numbers, which the study is doing, what's being looked at next?

David Modeer: Next is what is the most opportune way to augment the shortage. The difference between the demand and the supply on the river. The seven basin states together begin looking at things, including storing additional water as the it becomes available in the reservoirs, not using as much when you've got extra water, looking at desalination projects, whether it be brackish groundwater, which is plentiful in Arizona, locally and in the Yuma area. Looking at California and states that are near the ocean, looking at desal nation to offset demands on the river. And certainly lifestyle changes in which we use less water in the future.

Ted Simons: Thanks for joining us.

David Modeer: It's a pleasure, thank you.

David Modeer: Gemeral Manager,Central Arizona Project General Manager;

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