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Surprising Way Climate Change Is Impacting Water

Hydroclimatologist Bruce Daniels has analyzed 85 years of rainfall data collected all over California. He talks to Water Deeply about what he’s found and what it means for the state’s groundwater.

Written by Tara Lohan Published on Read time Approx. 6 minutes
A sign warns motorists of flooding on Highway 101 on March 10, 2016, in Corte Madera, Calif. Scientists are analyzing the impact of higher temperatures on rainfall.Eric Risberg, AP

To understand what the future holds, sometimes we have to look at the past, Bruce Daniels has learned. Daniels is trying to help Californians understand future water availability by examining 85 years of daily precipitation records. His analysis has shown that water managers (and the rest of us) have some reason to be concerned.

Daniels holds a PhD in hydroclimatology from the University of California, Santa Cruz, although he originally started his career in computer science, including working on the first Macintosh computer.

“I wanted to do something with more impact and more value,” he said of his career change. In addition to his hydroclimatology work, he also serves as the president of the board of directors for the Soquel Creek Water District in Santa Cruz County.

Water Deeply recently talked with Daniels about his research, the impact of higher temperatures on precipitation and what to make of the Ridiculously Resilient Ridge.

Water Deeply: What did you find in your research about how precipitation changes will impact water resources in California?

Bruce Daniels: I didn’t use climate models. I used observations for climate. It turns out there are records kept all over the state. I found 50 stations that had at least 85 years of daily rainfall data and no more than 7 percent of that data was missing.

It was San Jose, Oakland, San Francisco, Santa Cruz, all the way down to San Diego. What I found by doing some statistical analysis, is that all over the state the storms are getting weaker in terms of how much precipitation you get per day in each storm and the storms are getting longer. It lasts an extra day or a few more days longer.

You’d expect with weaker but longer you might be getting about as much rain as before, and it’s close to that. There’s not been a great change in the total amount of rain. But of course there is this change in the pattern – and the time between storms is also increasing. So again, another pattern change.

I took those timing changes and I fed them into a hydrology model and found out that that the groundwater recharge over the next 30 years would be reduced by 7 percent. All over the state people are already having trouble with their groundwater – it’s going down, and they can’t sustain it.

Water Deeply: How should that influence planning by water managers?

Daniels: You shouldn’t expect things to be how they were in the previous century, for one.

Another thing is that the year before last we had the warmest temperature recorded in history by 3 degrees [F]. Every time the temperature goes up 1 degree, the potential evaporation increases by 4 percent and in fact, some of the scientists looked at that drought that we had and they estimated that something like 20 percent of the drought was caused not by lack of rain but by the fact that we had that temperature which caused the rain we did get to evaporate.

Water Deeply: We hear a lot about how higher temperatures are impacting snowpack, but less about how it impacts evaporation.

Daniels: There are lots of things feeding into this that some people, some groups don’t know much about about and they need to. I’ve talked to every water district in my county, Santa Cruz County. A few months ago I went to Albuquerque; there was a conference there and I gave a paper on these effects.

If things are changing, you need to know what those changes are, otherwise you can’t plan how to adapt to those kinds of things.

There was a paper a couple of years ago by three climate scientists; it was peer-reviewed, and they were saying that in the last half of this century there is a greater than an 80 percent chance of a 35 or more year drought, twice as extreme as we’ve seen in the last 1,000 years.

People who have never thought about doing desal, maybe they need to. People who never thought about doing [water] recycling, maybe they need to. People who never thought about using stormwater runoff, maybe they need to.

It’s shocking and surprising and slow to seep in but it’s the kind of thing that all of us need to be thinking about. The way things have been is not the way things are liable to be. And the way things are liable to be is going to be pretty spartan and tough to handle. So, let’s start thinking about it now.

Water Deeply: What has been the effect of the drought where you are in Santa Cruz County?

Daniels: This year, the El Niño we just got was the largest ever observed and normally with these very large El Niños we can expect 150–200 percent of normal precipitation. And here in Santa Cruz County we got 104 percent – basically an average year. It was not a savior.

It was certainly better than the last two years – they were extraordinary, too. Here in Santa Cruz in January [2015], that’s the wettest month of the year, we got zero rain. Sacramento got 1/100 of an inch. There are extraordinary things happening and it should be a wake-up call.

Water Deeply: What did you learn about the Ridiculously Resilient Ridge – the high-pressure system off the coast that blocked storms from reaching California last year?

Daniels: We get ridges here. That’s often the kind of thing that keeps our summers dry, if there’s a ridge formed. The ironic thing is that this ridge was very long-lived – it was 13 months.

Ten years ago, in 2005, a professor at the University of California, Santa Cruz, Lisa Sloan, and one of her graduate students did an analysis of what would happen if the Arctic’s ice started disappearing, which we know now it has. She predicted this [ridge] sitting in the Pacific Ocean off of California blocking the storms. The Resilient Ridge was predicted 10 years ago just from looking at climate change effects.

That’s been refocused. There was a study a couple years ago from Stanford that said this kind of Resilient Ridge thing is three times more likely with climate change.

Water Deeply: What else can we learn about how previous droughts have impacted this part of the world?

Daniels: We can see how we’ve done things to get around this. The typical thing for urban water systems is you restrict the water that your customers use – you raise the price, you put fines on people who use too much. That has been helpful this time in certain areas.

Like my water district, we have low usage. We were tasked with reducing usage by 8 percent. Our customers heard the cry and they reduced it by 35 percent. There were some areas of the state that did that. There were some areas that didn’t meet the 25 percent asked of them.

Water Deeply: You’re the president of the board for the Soquel Creek Water District – what does your long-term picture look like for water supply?

Daniels: We’re in bad shape. We have salt water intrusion all around us. For 30 years the boards in the past have pumped and pumped and pumped great deficits. The groundwater levels in many places in our district are below sea level, which is just drawing the salt water in. We need to fix that.

Water Deeply: Are you optimistic that we can do enough given the challenges that lie ahead?

Daniels: There are definitely things we can do. One of the things that is often mentioned is that we are going to get bigger storms, and in fact, a couple of the studies have shown that a normal winter, which is four months long – we get all of our rain in December, January, February and March – that in the future that will shrink to two months.

If we get these big storms that lots of people are predicting, you can put in reservoirs and holding tanks and even furrows to slow water as it goes down the hill and give it a chance to soak in. Those are the kinds of things we can do to compensate for some of the climate change effects that are going to happen.

Basically, the more we know, the better we can do. There are things that can be done. We have to be clever, we have to be hardworking, we have to invest in these kind of things. I think we can do the things we need to do to make this work. It’s not going to be easy, but what’s the alternative?

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