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August 13, 2012 | A longtime environmental leader and water policy expert, David Behar is one of the nation’s leading voices on how to weave weather and climate knowledge into water management. He currently serves as climate program director for the water enterprise at the San Francisco Public Utilities Commission, which is the nation’s sixth largest municipal water provider. In 2007, he organized a summit that evolved into the Water Utility Climate Alliance. This coalition of 10 large utilities from across the nation works to foster collaborative research and to help water utilities mitigate and adapt to climate change. Behar is also involved in a pilot project on tailoring climate model output for water management, an effort organized by the new societal dimensions working group of the NCAR-based Community Earth System Model.
I think it’s increasingly seen as an important part of understanding how to operate our systems in the future. The larger drinking water providers in the country are leading the way, but there are a number of smaller agencies, here in California and elsewhere, that have done some very thorough and sophisticated work in assessing the impact of climate change on their systems.
What climate change means is that past practice is no longer a good indicator of how we need to view the future. In the water business, we traditionally look at the stationary hydrologic record and use it as the boundary for how we might operate in the future. We know we can’t do that anymore.
The vulnerability in the Southwest United States is completely different than the vulnerability in the Northeast. In my region, central California, we’re on the coast and most of our water comes from the Sierra. We’re concerned about upward trends in temperature, particularly minimum daily temps, and we’re concerned about possible changes in precipitation. To a degree, the climate models are still providing mixed signals on precipitation in our region. That makes planning and thinking and assessing more difficult than if there’s a clearer signal emerging.
Also, there’s a diversity of political frameworks in which people operate. In some places, if you’re not acting now with respect to climate change, your constituents will think you’re falling behind. In other places, it’s sometimes difficult to even use the words “climate change,” because of the politicized nature of this issue. So one size absolutely does not fit all when it comes to effects, assessment techniques, or the politics of climate change.
Water demand has plummeted nationwide over the last three years by about 10 to 20 percent. Here in the Bay Area, it’s down by 15 to 20 percent. It’s actually resulted in a financial crisis for water districts everywhere. Water use is where our revenue comes from, and we have high fixed costs, so we’re sensitive to fluctuations.
Nobody really knows why this is happening, but it may be a mix of three factors. One is the economy, which is creating price elasticity for water—which is a very cheap commodity—along with causing vacancy and foreclosure rates that can drive down water consumption. The second factor is weather, especially in California, where we’ve had a series of unusually cool summers. The third factor is the conservation ethic, which is penetrating to the public after a lot of education over a lot of years, even in a non-drought context. The economy may be the main factor. Usage is going back up this year in many places, but I don’t know if it qualifies as a reversal of the trend.
Our bayside storm collection system is already being affected by rising sea level. We're investing $20–40 million to deal with these effects. It’s one of the only examples in the United States where climate-justified adaptation planning and spending is under way.
By and large, we’re still in an era of assessment rather than adaptation in the United States. Here in the Bay Area, we’re in the process of trying to figure out what we know, what we don’t know, and what it all means.
We like to say that water managers know uncertainty. We deal with it every day, every month, every year. Weather is a subset of climate, and in the West, each year’s weather can be very different than the year before.
We know how to operate with drought, but the drought we plan for is our drought of record. It’s consecutive dry years that create the greatest vulnerability for the greatest number of people. Understanding how those are going to change is really important. A lot of people have used the paleoclimate record to envision droughts that could last 20, 30, 40, or 50 years. There’s no way to prepare for a drought like that in terms of infrastructure.
We are used to changing conditions year over year, but I sometimes refer to the qualitiative paradox that emerges from climate science. We hear that extreme events will get more extreme, droughts will get stronger, intense storms will get more intense, but we don’t know by exactly how much. We’re left with a qualitative projection of the future that is difficult for us to plan for, because we’re engineers, and the amount of molecules of water in our reservoir at the end of each year is what ultimately matters.
In snowfed watersheds like ours, the timing of runoff changes as a result of temperature changes, because more precipitation falls as rain and the snow melts sooner. At my utility, we’ve completed a sensitivity analysis that laid out six different scenarios, from optimistic to pessimistic, for temperature and precipitation at three points in time: 2040, 2070, and 2100. Runoff varies widely. If you look out to 2100, we can see an increase in runoff of a few percent, down to a decrease of 29%, depending on which scenario you pick. It’s a very wide range, and it doesn’t lend itself to planning at all.
We’re all struggling with how to use the information we have today to prepare for tomorrow. One of the top priorities of the Water Utility Climate Alliance is to build bridges with members of the science community who want to build bridges to us, especially those doing adaptation science. Those scientists are interested in having ongoing, collaborative conversations and building relationships with decision makers like us that will be fruitful over time. We need more of those.
The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under sponsorship by the National Science Foundation. Any opinions, findings and conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.