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New Study Says Forecasters Are Overestimating Future Demand For Water

 August 11, 2020 at 10:13 AM PDT

Speaker 1: 00:00 We have grown used to the idea that water is a precious commodity in California. One that we risk running out of. If we do not conserve a new report out of the Pacific Institute, suggest we have learned to conserve so well that water forecasters need to rethink their approach to future water supplies. Alison st. John spoke to Pacific Institute researcher, Sarah Deringer about the findings of the report. Here's that interview? Speaker 2: 00:27 Oh, you've done many studies in the past warning that we risk running out of water here in California, but this one is different. You say, agencies are overestimating, how much water we actually need? Why is that? Speaker 3: 00:38 Well? So what we did was we looked at the 10 largest water utilities in California and found that water demand between 2020 15, actually declined by 18%, which means that even with population growth, we're using less water per percent than we used to. And a lot of what that comes from is increasing number of water, efficient devices. So our toilets use less water to flush clothes, washers, use less water, but we're still estimating that our future demands will come from these high water use devices. And so we're overestimating how much water we may need in the future. Speaker 2: 01:14 You say the forecasts were dramatically overestimated by how much were they wrong? Speaker 3: 01:19 It varied from water utility to water utility, but on average, they were consistently over by 20% or more on future water demand. Some of them up to 30 plus percent and how much was expected to be needed in 2015 compared to what we actually needed. Speaker 2: 01:35 You sight washing machines and toilets, low flow toilets, things like that. Is it only residential water use that has dropped more due to conservation or are businesses also saving more water than we expected? Speaker 3: 01:46 It's been a mixture. Most of what we looked at was total water demand, mostly for residential, but there are similar trends in, um, in businesses and commercial spaces. Um, and the other thing I should say is that while a lot of it is from these devices, there also has been some changing, uh, water use and conservation and how we think about using water. And what do you mean by that? As you know, we had a pretty big drought, um, during the two thousands. And that really changed how people started to think about the importance of water and what it might look like. Not to have enough. And so Californians really spent a lot of time and energy thinking about how do we make conservation a way of life. And so during that time period, um, people started to, to change out some of their landscapes, less water use on their lawns, thinking about whether they needed to wash their cars as frequently. Those sorts of things. The other piece is that there just continues to be better and better technology that helps us to save water even while we do all of the things we need and want to do around our home. Speaker 2: 02:47 So what is the implication of these findings that people have been forecasting water use much too high? Speaker 3: 02:53 It's a great question. So overestimating demand can mean that we're investing in bigger and more expensive water supplies that we may not need in the future. So for example, if a forecast is saying that 20 years from now, we're going to need 20% more water. The water agencies are likely to start investing now in infrastructure that can help us to meet that demand. But if that demand never comes to be, we ended up having assets. We may not need, it's very expensive to plan for infrastructure that way. So it could be affecting our present water bills, right. It could be, do you have any examples of water investments that have already been made that are in excess of what will be needed hard to say, because we never quite know what the future will look like. So it's hard to know right now, what will end up being investments that we don't need in the future. Speaker 3: 03:44 Does this mean that we can see population growth and more housing density without fear of running out of water? There is going to be a challenge throughout the world and certainly in California of having increase in population and needing water to support those populations. But I think it's more of a question of growing in a smart way and growing in a water efficient way so that we can make sure we're supporting our communities as they grow. Now. What about climate change? Could that derail all our forecasts? Absolutely. There's, there's no question that climate change is really going to disrupt forecasts in general and also our ability to make good forecasts. And I think that highlights even more of the importance of bringing in information that we do have. So we have a lot of information on how people are using water now that we could be bringing into forecasts to be doing a better job so that when these climate impacts continue to exacerbate challenges, that we're a little bit more capable of figuring out what we need in the future. Speaker 3: 04:43 What are you recommending as a result of your findings? Well, one of the big recommendations is really around evaluating water use trends. And so it's really about taking note of what's happening around us and using that to improve the accuracy of these forecasts. And we also recommended that there should be, um, more helpful state guidelines and resources for improving these forecasts throughout the state and making sure that we're really projecting out how much water we'll need in, in a more accurate way. I assume that your conclusions do not imply that we should stop trying to conserve water, right? Oh, absolutely. I think in some ways it shows the opposite that we, if we continue to conserve water, that we actually can bring down the future water demand even further and make our water bills even less in the future that we won't need to be investing in large infrastructure. Um, and it also shows that we have a lot of capacity within our homes and within our businesses to be conserving more water than we even expected. Speaker 1: 05:42 That was Sarah. Darren's your senior researcher with the Pacific Institute speaking with KPBS host, Alison st. John.

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A new report from the Pacific Institute suggests we have learned to conserve so well that water forecasters have radically overestimated the amount of water we will need in the future.
KPBS Midday Edition Segments