At the National Water Research Institute’s Drought Response Workshop, October 8, 2013, John Leahigh, Principal Engineer for State Water Project Operations at California Department of Water Resources, gave a briefing on the outlook for operations of the State Water Project in the coming year. During his presentation, he discussed the challenge of the newer, variable regulatory requirements in planning for operations of the project, as well as how water allocations are determined.
John Leahigh began by saying he has been involved with water management activities for the State Water Project for the last 15 years, and the project has had shortages for all but two of them.
The big difference between the State Water Project and the Colorado River supply is the large amount of uncertainty that is associated with the State Water Project, said Mr. Leahigh, noting that about the only thing that is known are storage conditions, which is relatively small compared to the storage available Colorado River system.
“California’s system is highly integrated and I think that is one of our big advantages,” he said. “It does allow for water transfers and water exchanges throughout the system with the customers having multiple sources from both the Colorado River and the State Water Project.”
“The integration really starts up in the project at the largest dam in the U.S., Oroville Dam, impounding 3.5 MAF of storage in Northern California,” said Mr. Leahigh. “We operate in conjunction with the Bureau of Reclamation with Shasta and Folsom reservoirs, and we’re jointly responsible for meeting all the flow and salinity requirements in the Sacramento-San Joaquin Delta.”
State Water Project customers include contractors up near Oroville, urban contractors in Solano and Napa County, the Santa Clara Valley Water District, Kern County Water Agency and Tulare Lake Basin, with the majority of the water going to Southern California and in particular, the Metropolitan Water District.
Close to half of the State Water Project water goes to the Metropolitan Water District, and about a quarter goes to Kern County Water Agency; close to two-thirds are for urban supplies, said Mr. Leahigh, noting that the State Water Project provides at least a portion of the water supply for 25 million Californians and irrigates over 750,000 acres of cropland in the Central Valley.
There are two types of uncertainty in regards to State Water Project operations: hydrologic uncertainty and regulatory uncertainty, he said.
California’s variable runoff is a big factor, he said. “We have spatial inequity and we also have temporal variability with our supply in California,” he said, displaying a chart of the history of precipitation for the Sacramento Valley. “My hope is that the wet years are underrepresented in the last 10 or 12 years, so its gambler’s folly, but I am going to go for a wet year next year.”
Seasonal variation is also large, said Mr. Leahigh, presenting a chart displaying how Delta inflow varies month by month throughout the year. “Most of the runoff occurs in the spring period, February and March, so to the extent that we’re not able to capture it either upstream, due to capacity constraints or flood control requirements, or we’re not able to export it because of environmental restrictions in the Delta, that’s a loss of that volume of water to the project.”
He then presented a graphic which showed the standard deviation of annual precipitation versus the mean annual precipitation. “California is uniquely variable as it relates to the rest of the country … you can see that by far, California’s supply is the most variable. We rely on 10 to 15 days in the winter to produce 50% of our water supply.”
So what was the story this year? He then presented a graph of the Northern Sierra 8-station index, noting that the wettest year is in green, the driest in brown, with the year 2012-13 shown in red. “What we’re showing here is the dichotomy that we saw as far as precipitation in Northern California this year,” said Mr. Leahigh. “It was a very wet fall in 2012 – November and December were actually in the top 10% for those months in the historical record, and then it just shutoff completely. For awhile there, it was the driest calendar year. June turned out to be a little wet, and September was actually about 200% above normal, but it did bring us above the 1924 year, so second driest calendar year, to date. It made a big difference. You can see we almost ended up average, but the runoff was well below average, in fact it was classified as a dry year for the Sacramento Valley and a critically dry year for the San Joaquin Valley.”
The other big variability for the State Water Project is regulatory. “We are conveying our water through the largest estuary on the west coast of the Americas with a degraded and collapsing ecology of the Delta; a number of the species continue to be listed,” he said. “New regulations have been put on the project and its ability to export water in that fishery sensitive period which is the spring and is also when most of the runoff is occurring into the Delta, so it is in direct conflict between the water supply and the protection of the fish.”
The State Water Board’s Water Quality Control Plan establishes the salinity and flow requirements that the Department of Water Resources is jointly responsible with the Bureau of Reclamation for meeting, said Mr. Leahigh. It was last significantly updated in 1995, and is currently under review. “There could be some pretty major changes that come out of this current review process. There’s talk of looking at requiring much larger flow requirements and requiring a certain percentage of full natural flow to pass through the reservoirs so that’s in a process that will take at least a couple of years to get through. But the standards that we do operate to now under the water quality control plan are fairly prescriptive standards. They vary by month, they vary by hydrology, they vary by year type, but we can plan to them.”
However, the newer requirements that have come as a result of the biological opinions in the last few years are different, he said. “The new regulation is to mitigate the reverse flows on the Old and Middle River in the Delta. These flow requirements are not prescriptive; they are highly variable and they are dependent upon ecological triggers, so for example, turbidity in the Delta or the actual distribution of fish that are found in the surveys of the spring. The range of targets for the Old and Middle River flow requirement is highly variable – it can vary by up to 4000 cfs on any given day. … These flow requirements are set by the two federal fishery agencies on a week to week basis from about late December through June, so we don’t know from week to week what flow requirements the projects will need to meet.” He said that extrapolating the range of 4,000 cfs over the entire six month period gives a range of 1.5 MAF for both the state and federal projects, or about 750,000 acre-feet of variability for the State Water Project that is associated with the new regulation.
“The more prescriptive standard fits very neatly in a model – it’s prescriptive, it’s a certain value, per month, per year type so that one we can model very well,” said Mr. Leahigh. “The NMFS and FWS biops regulations are a real challenge to get a handle on how it will affect the supplies of the project from year to year. Much of this is for the Old and Middle River flow requirements.”
Determining the State Water Project Allocation
“There’s enormous uncertainty associated with both the hydrologic and the regulatory components of project operations,” said Mr. Leahigh. “The only thing we do know is what our starting storage is coming into 2014,” noting at the time of the conference (Oct 2013) that Oroville, the largest reservoir on the State Water Project, was about 70% of average to date.”
He presented a graph of storage levels in Lake Oroville and noted that the reservoir is a couple of hundred-thousand acre-feet behind last year. “We were actually able to fill Oroville last year. We didn’t fill this year. You can see also the red line [2012 storage] take a dramatic increase in December which was that very wet fall period that we saw last year … that’s really what saved us, we were able to store some of that water early on. We’d be lucky to see that kind of increase towards the end of this year in storage and so it looks like storage is going to be fairly low going into 2014.”
It is the carryover storage in Lake Oroville that allows us to mitigate for the first year of drought, but by the second year, we’ve pretty much depleted that carryover storage, he said.
He then presented a similar graph for the state’s portion of storage in San Luis Reservoir. San Luis Reservoir, a joint federal and state facility, is cycled through on an annual basis and isn’t really used for carryover storage, he noted. “We really never made much progress in filling San Luis this year,” said Mr. Leahigh. “Those first big rains in November-December, there was a significant amount of runoff. Unfortunately with the additional flows, the turbidity triggered an earlier Old and Middle River restriction action than we would typically see. This really prevented us from any significant export in that crucial spring period where typically we’d be filling San Luis. … This is where maybe a couple of tunnels under the Delta would have come in handy potentially.”
The Department of Water Resources initial allocation is a very conservative one, given the hydrologic and regulatory variability, he said. “It’s based on the 90% exceedance, so we’re always very conservative on those initial outlooks.” As time goes on, we’re getting a better handle on how the newer environmental constraints from the biological opinions affect project operations, he said. “We know that we’re not going to be restricted to the most restrictive action for the entire 6 month period and it’s likely not to be the least, either, so over time we’re getting a better handle on maybe what’s the most likely level of control for these new environmental constraints and we’ll factor that into our allocation decisions. The big known would be the initial storage conditions and unfortunately, going into 2014, the one known factor is not very good.”
Other factors considered when making the allocation decisions are the actual demand pattern from the contractors and other physical regulatory constraints, such as flood encroachment space in Lake Oroville or pumping constraints in the Delta.
He then displayed a graphic of a sample run of the Cal-Sim model that they use for estimating the allocation. “We run [the Cal-Sim model] in position analysis mode where we actually take a look at our starting initial storage conditions; we then run 82 years of historical hydrology starting with those particular storage conditions and see what kind of allocation we may come up with,” he said. “We haven’t run it yet for 2014 until we get a better idea of where we’re headed as far as initial storage; but this gives you an idea of the uncertainty. On the horizontal axis is the hydrologic uncertainty – this is anywhere from very extreme years of getting close to no allocation … The vertical axis represents the regulatory uncertainty, so even within an average year, there could be a big difference even based on what type of regulatory constraints we might see in that particular year.”
“By contract, we provide an initial allocation for the SWP contractors by December 1st; we update that as we step through the winter as far as how much snowpack is accumulating in the northern Sierra,” he said. “We receive updated runoff forecasts from the Division of Flood Management within DWR; typically the final allocation is made by May or June.”
He then presented a graph of State Water Project allocations for the past 15 years. “You can see that shortages are really par for the course as far as SWP allocations are concerned,” Mr. Leahigh said. “The prior 30 years, from 1969 to 1999, there were only 5 years where we shorted the requested deliveries. Since then, there’s only one year out of the last 14 where we actually met all of the requested deliveries of the State Water Project. That’s for a number of reasons, one of them being that the demands on the project have been increasing over time, so the requested amount is much larger than it used to be. The requests are coming in close to that 4 million acre-foot mark since about 2000; it’s been commonplace that we’ll have the request for the full 4 million whereas earlier, in the 90s, it was more like 2 to 3 MAF, so we were able to more often meet those requests.”
“We’re getting higher demands and we’re getting squeezed on the supply side as well [from regulatory constraints] and so that accounts for the normal shortage that we are experiencing, drought or no drought, for the most part,” he said.
Outlook for 2014
What is the outlook for 2014? Mr. Leahigh began by recapping the last four years. Well, we can kind of recap what’s happened in the last four years. “In 2011, we came off of a below-normal year in 2010, so we had fairly low storage to begin with. Our initial allocation was 25%, again that’s a conservative estimate of the coming year. Turned out, it was a very wet year and so the final allocation was actually 80%, so a big improvement over the year.”
“In 2012, because the previous year was so good, we had very high initial storage and so we had a very high initial allocation at 60%. It turned out to be a little sub-par as far as hydrology, so we only inched up a bit on that initial conservative estimate so we could finish the year at 65%,” he said. “In 2013, this past year, we had low initial storage because of the below normal conditions. Oroville can only mitigate for the first dry year, so that’s why we got a decent allocation that first dry year, 2012, but storage was depleted in 2013 so it was a 30% initial allocation. Initially we did increase the allocation to 40% in December as a result of the very wet conditions early on in the water year, but then when things turned around on us, we did have to actually have to drop the allocation, even though we made a conservative estimate, because it was near driest on record. We did have to reduce that allocation later in March, and so our final allocation ended up at 35% for this year.”
“So what do we know, going into next year? Really the only known is that we’re going to have even lower initial storage going into 2014 because it represents the third dry year,” said Mr. Leahigh. “The assumption is again that it will be dry. That’s always the assumption, as far as the initial allocation is concerned. So we are expecting a very low initial allocation on the SWP. You’ll be hearing that by December 1st exactly what that number is.”
For more information:
- Click here for John Leahigh’s power point presentation.
- Click here for all videos and presentations from the workshop.