Deluge and Drought

During the past several months, California’s skies have unexpectedly opened up and drenched the state with rainfall. Prof. Joseph Reichenberger discusses whether the state’s multi-year drought finally is over.

Joseph Reichenberger

This year’s rainy season hit Californians like a bucket of cold water — hundreds of thousands of buckets, to tell the truth. We spoke with Joseph Reichenberger, professor of civil engineering and environmental science in the Frank R. Seaver College of Science and Engineering about the state’s drought conditions and water issues. He has 50 years of professional engineering experience in public and private practice in water, wastewater and recycled water systems, water and wastewater treatment and treatment facility hydraulics. He also has served as a director of the San Gabriel Valley Municipal Water District and as a commissioner on the San Gabriel Basin Water Quality Authority. Reichenberger was interviewed by Editor Joseph Wakelee-Lynch.

How would you characterize the rainfall we’ve seen over the past several months?
It depends on where you are considering. Here in Los Angeles, the rainfall has been close to the normal, or annual, average based on the county’s data. But if you take a look at what’s happening up north, particularly in the northern Sierras, it has been a bonus year for water. The snowpack is exceptionally high, at near-record levels.

A year ago, it seemed impossible to imagine that the next rainy season would overcome statewide drought conditions, but would you say that has happened?
Certainly this year was a bonus year. If this were to continue for the next several years, then, yes, we would probably offset the drought. But we’re still probably a long ways from having offset the five or six-year deficit. We’ll have to do the best we can with what we have, particularly with the snowpack and being able to move that water to places where we can store it.

We have a good snowpack as a result of the rains, but what is the impact on groundwater supplies?
There have been media reports about banner years up north, but the groundwater basins haven’t recovered. First of all, it’s going to take a while for the natural rainfall to penetrate down into the ground and manifest itself in increased levels. Also, most of our groundwater basins, particularly here in Southern California, get their replenishment from two sources: natural rainfall and imported water. The county flood control district in Los Angeles owns and operates the percolation basins, and in the wintertime, they prefer taking native run-off as opposed to bringing imported water and spreading it. If we were able to take imported water during the wintertime, of which this year there has been ample water available, then that water could’ve gone into the basins to be spread. But that isn’t always possible, due to the restrictions on their operations. So over the summer, when we don’t have any native rainfall to spread, they’ll bring down captured mountain run-off but also imported water will come in and the basins will come up. The basins in San Joaquin Valley will probably come up as a result of the farmers coming off of groundwater and using surface water. That will bring up the groundwater basins because we’ll stop pumping and the natural replenishment will come back.

 

Where does imported water come from?
Imported water comes from the Colorado River and the Owens Valley Aqueduct, which had a record year due to the snowpack on the eastern side of the Sierras. So there will be plenty of water for city of L.A. to use and spread. The rest of it will come from Northern California, which had a bonus year also, through the California Aqueduct.

The Oroville Dam in Northern California was under great pressure this rainy season; what does that tell us about storage capacity in California?
There was a structural failure on the spillway, quite catastrophic. To avoid using what we call the service spillway, because they were concerned about the damage, they allowed the lake to fill, which went over the emergency spillway. The emergency spillway functioned pretty well as designed. When you design an emergency spillway, you hope that it is never used. This was the first time it was used in 50 years.

It’s interesting to think about the water that was lost in Oroville. They were discharging 100,000 cubic feet per second out of that spillway, and that amounts to 200,000 acre feet of water in one day. The Metropolitan Water District of Southern California typically takes out 2 million acre feet a year out of the Sacramento Delta. So, in a week and a half the water that was lost equals what Metropolitan takes out in a year. Where did that water go? That water went out to ocean, so it was lost. Why was it lost? Well, we don’t have enough storage capacity in Oroville and a lot of the other reservoirs.

Oroville had to be maintained for flood protection and in anticipation of the snowmelt. The rules of operation say that the water levels at a certain time of year, like the springtime, shall be maintained below a certain level. If it gets above that, they have to discharge water, and if there’s not place to put that water it’s going to go out to the ocean. The San Luis reservoir, which is an off-stream reservoir near Los Banos, was nearly empty at the start of this rainy season and is now essentially full. Castaic and Pyramid Lake are essentially full. Most of the reservoirs in Southern California if not full are certainly nearing full. There’s just no place to put the water. And it’s going to get worse in the future due to climate change.

Right now, we have a very nice snowpack. It’ll run off in traditional fashion, and the reservoirs should be able to capture much of it, though some will be lost. These reservoirs that were built in the 1960s, and some before then, were designed for snowpack. With climate change, we’re not going to have snowpack. Our precipitation will be in the form of rainfall, and that’s going run off immediately. There’s no place to store it. The reservoirs aren’t designed for that. So in the future we’ll have more severe storms and greater run-off. It’s imperative that additional storage be developed as well as the ability to convey some of these high flows to places where we can store or percolate the water into the ground. It would be great if we could get this water out of the Sacramento Delta and into Southern California where we can spread it. To get water out of the Sacramento River also would reduce flood potential by easing the pressure on the levees, which are near the breaking point.

Do you see any evidence that lessons have been learned by those whose decisions affect the state’s water system?
First, we’re realizing this was a wake-up call to the fact that we don’t have storage and we’ve wasted an opportunity to store a lot of water. Who knows what the rainfall will be like next year? It would be nice to have that several million acre feet that probably wasted out to the ocean this year.

Another thing being considered is the revision of reservoir operating rules. All dams have to have operating rules concerning what levels must be maintained during certain times of the year, particularly multi-purpose reservoirs that serve water supply and flood control. With a water supply reservoir, we want to maximize storage, yet with flood control we have to be careful because if we let the water level rise too much we won’t be able to effectively control floods. Operating rules were developed some 50 years ago when our weather forecasting wasn’t as good as today. With a more effective understanding of meteorology, hydrology and weather forecasting, we might be able to do a better job of operating the reservoirs to maximize storage and maximize flood potential at the same time. Those are things that scientists and dam operators and owners are looking at.

The key is the state legislators coming to the realization that we need more storage. Until this year, there was a lot of talk such as “Why do we need more storage? We don’t have enough water to fill the existing storage.” That’s true. If you looked around, every reservoir was drained. But with climate change, we’re going to see more extremes both at the precipitation end and at the drought end. So how can you accommodate that change through storage? We’re going to need more storage. Yes, there probably will be more reservoirs that will be low, but there also will be more reservoirs that will be full when we get a chance to capture the water.