Study finds that by building new storage and integrating their operations with existing storage would increase water delivery by 400 TAF/year on average and over 700 TAF in dry years
In July of this year, the Association of California Water Agencies (ACWA) released a study, 21st Century Water Infrastructure: New Approaches to Create Flexibility and Resiliency, which examined how the state’s water supply system could operate more flexibly and effectively with the addition and integrated operation of new storage capacity. At the August meeting of the Delta Stewardship Council, ACWA’s David Bolland provided an overview of the study for council members.
“The study was prepared by MBK Engineers for ACWA, and is one of the only storage studies which analyzes the integration of existing and potential new storage projects and their operations,” said Anthony Navasero, Senior Engineer with the Delta Stewardship Council. “This study is another tool to assist decision makers to evaluate and prioritize storage projects and their benefits.”
David Bolland, Director of State Regulatory Relations for ACWA, began by noting that the Association has been working on this issue for some time. “The Association has 430 or so public water agencies up and down the state of California, many of which are heavily involved with storage projects and individual projects, as well as systems operations considerations,” he said. “We’re engaged in a lot of levels with state policymaking on storage as well as water management in general, and so in that context, we wanted to zero in on this question of potential and do some analytical and quantitative work to get at this premise that an investment in new storage could really help us out.”
This winter, we he had a lot of precipitation across the state, but one of the criticisms was all of that water moving through the system and out to the ocean when it was needed for groundwater recharge, he said. “We have a lot of work left to do in terms of groundwater recharge and water management in general, moving water around the state and using it more effectively, and that was the policy context for why ACWA undertook this study.”
The overarching considerations and the policy context for the study was that ACWA and the water agencies in California recognize the fact that water remaining in the ecosystem has value and water flowing through the ecosystem provides benefits, such as salinity management, water quality, and ecosystem values, and that has statewide implications as well, said Mr. Bolland. “When water is abundant, we think we can manage it and if we do manage it in an effective way, we can add significant value to both the supply side as well as the ecosystem.”
Mr. Bolland said that the study does not presume that all water would be going to consumptive uses for cities and farms, but that it would be used by state effectively to meet all of the goals, specifically the coequal goals that are in the center of the Delta planning process, but that concept of coequal goals has been brought to a larger scale in statewide water management.
“It’s pretty much an assumed conclusion on the part of the agencies I work with and the Association that the coequal goals are kind of the rules that we’re going to be living by henceforth in all kinds of management decisions,” he said. “We also wanted to emphasize that we’re studying a potential here, based on a suite of projects, some of which are the existing system and some of which are being proposed on this existing system, and we wanted to look at how those projects interact with each other, how they interact with the existing system, and then what can be done with conveyance improvements, so we have a with or without conveyance improvements in the Delta, and then this idea that we can make some progress on groundwater recharge is the context as well.”
Many policy documents by ACWA and the state have called for storage improvements as part of a robust, ‘all of the above’ management scenario, such as the ACWA Blueprint in 2005, the Delta Plan, ACWA’s State Water Action Plan, and the California Water Action Plan. Then Prop 1 passed in 2014, which had $2.7 billion for storage. ACWA provided some policy direction and recommendations for storage investments in their 21st Century Storage Policy in 2015. ACWA’s integration study is intended to inform the Water Storage Investment Program process, as well as other policy contexts such as the Delta PlanConveyance, Storage, and Operations Amendment and other decisions that the state is making.
The Water Storage Investment Program funding decisions will occur in 2018, with funding allocations anticipated by 2022, Mr. Bolland said. “I think what we’ll find as we look at this study is that no matter what the WSIP program does, and no matter what we do with that Prop 1 money, there certainly is a larger mission that California is on to increase storage above ground storage, as well as increase the value of and the sustainability of our groundwater storage aquifers.”
The study looks at comprehensive solutions for water quality and water supply challenges in California – not only surface storage and groundwater storage, but also with and without new conveyance, stormwater capture, recycling and desalination, conservation, demand management, transfers, and even the significant need for investment in forest management and our headwaters.
“The hypothesis is if you add a whole suite of new storage, some above the Delta, some below, some surface, some groundwater, some big, some little, some regional scale and some potentially statewide scale, that there’s a benefit that will be derived that is bigger than the sum of the parts,” said Mr. Bolland. “There’s an integration benefit and an ability to measure that and lay that on the table … We wanted to make sure that the discussion was out there because there’s a tendency in the policy arena to try to pick winners and losers, which project’s the best, where exactly should we spend a certain amount of money, and to be kind of more narrowly focused, and the point here is that we want to focus on the big picture statewide.”
There are eight projects evaluated in the study; six of those have submitted applications for Prop 1 funding. “The way we’re looking at this list is that we’re not here to try and promote any particular projects; the emphasis is on this integration and the results of integration with this suite of projects that we had a year ago that we could analyze as part of our modeling,” he said. “The key theme is the fact that each of the projects bring specific attributes, but the magic is the way those attributes are managed in an integrated way.”
The operational assumptions in the modeling were existing regulatory requirements, existing management responsibilities, flood flows, storage operations, and all of the assumed status quo; they added the projects, and then performed the analysis with and without the California Water Fix.
Mr. Bolland presented a slide showing the locations of the eight new storage projects considered in the study, and noted that if all eight projects were built, it would add 3.5 MAF of storage to the system.
The first step in the analytical process and the modeling process was to determine whether or not there was any water in the system to actually fill these reservoirs, he said, noting that the arrows in the boxes point to different kinds of water years in different parts of the system. “That is where the water is in the system geographically and then temporally by water year types, and one theme that’s going to come up time and again is variability,” he said. “This system is extremely variable and as we did the hydrology and actually modeled this; it was all based on historical, 82 years of hydrology in the system, and you’ll see tremendous variability by water year and then by geography.”
One of the questions was the possibility of Delta outflow above existing requirements, and the variability is the thing that jumps out here, he said. “We did the top chart, which shows a monthly averaging; of course, averages are interesting but not necessarily applicable in terms of water management. Even more eye-opening are the annual totals and you can see the variability in the system.”
“We identify the fact that there is some existing available export capacity that could be integrated into the system,” he said. “Then the idea was to link the facilities that are north of the Delta to the south of the Delta.”
“The results, after we layered in all these projects, is that things range from about 22 MAF in wet years to about 1 MAF only in critical years, and there’s an average of 10 MAF across the entire 82 year analytical period. Again with 3.5 MAF potential addition to the system.”
“The big yields come from the idea of additional flexibility and reliability and the ability to actually manage the water in a way that leads to increased coequal goal benefits,” Mr. Bolland said. “So what we have to work with essentially is a new additional carryover of about 1.9 MAF on average. That carryover can be used in a lot of different ways … An example is cold water. A very specific example that our modeler identified was in the 2015 water year, if we had had these reservoirs in the system, we would be able to preserve a lot more cold water in the Shasta system and the move water for other purposes that was warmer and further down in the system, move that through for salinity management and other regulatory objectives, and then we would have been enable essentially to achieve our temperature objectives through the entire year, even though 2015 was a drought year.”
Adding new storage and integrating operations of new and existing storage would increase water deliveries by about 400,000 acre-feet south of the Delta for various purposes, much of which would probably be moved into groundwater, he said. “In dry years, up to 700,000 acre-feet, and even in critical years up to 400,000 acre-feet, and that’s pretty important,” he said.
“It’s the result of having the capability of storing that water when we can get it – the big gulp, little sip or the idea of storing the water when its available and then moving it through the system when there’s capacity in the system which is actually in the dry and critically dry years, and that’s why that dry year number looks so big. How can you get water out of the system in the dry years? You’re using the capacity and storage, so you’re using water that was actually captured in the previous years and moving it through the system in the dry years.”
Mr. Bolland presented a graph showing the results with and without improved Delta conveyance, noting that the graph on the left shows without Delta conveyance improvements and the graph on the right is with Delta conveyance improvements. “On the left, it’s just adding storage to the system and using existing conveyance that we have in the Delta and operating it just like it currently operates, and then if we have the Delta fix, you can see it almost doubles the numbers in almost all the years. The one interesting thing is that it doesn’t change things in the critical years, and again that’s about capacity in the system; just there isn’t really a lot of water to move through. But it substantially improves wet and normal year deliveries.”
Another question was how much available water are you moving into storage that wouldn’t be for ecosystem flow values. “We wanted to quantify that and so this shows the stored and delivered water under this sort of modeled scenario as a relatively smaller proportion of the total, and so in all year types, significant amount of water remains in the system and is moving through the system, and we’re just taking a certain percentage in every year type,” he said. “Of course those percentages are relatively larger in the dry and critically dry years, which is a policy question that would need to be answered by some rigorous management, because it’s up to 20 or 25% of available water in those years.”
Mr. Bolland then presented a graph showing the potential for improved groundwater conditions. “Basically with existing conveyance but this new suite of storage, we get the red line over 80 years, and at about 250,000 acre-feet per year, you end up with a fair bit of water in time,” he said. “Of course, that does not alleviate the groundwater overdraft problem we have entirely by any means, and it makes it clear that there are going to have to be other means used in terms of groundwater management as a whole, but with conveyance, you again get almost double the amount of water, 460,000 AF per year, and the key again is you can move that water from where it is to where it could be much more effectively with improved Delta conveyance.”
Mr. Bolland then gave some examples of the benefits of integration. “The CVP-SWP reservoir operations process and protecting storage north,” he said. “And then creating benefits in cold water, and the projects can be operated conjunctively to do that – the Sites, Centennial, and American River conjunctive projects. Basically what’s that about is capturing water that currently is going through the system below the Shasta system, moving it across the valley, and then moving it down through Folsom. Folsom is capacity challenged, so the idea is you operate that in a just-in-time way, moving water now that we would have to discharge when we won’t need it into the Delta, moving that into groundwater storage at a regional scale, and then pumping and using that and running it down the American River system and into the Delta when it is needed for temperature or salinity requirements, and so it provides that additional water resource where it needs to be at the right time.”
With integration within the export service area, water can be moved through the Delta, or it can be moved into Los Vaqueros or into San Luis Reservoir, and then over the longer term, be recharging those groundwater basins, he said. “There’s been a policy question of why can’t we just have all groundwater recharge storage type projects, but you need both,” he said. “You need surface storage to capture it when we’re in the peaks, and then you need to be able to move it into storage when we’re not in the peaks, and so that’s how this system operates.”
Mr. Bolland then gave the study’s key conclusions. “There is significant water available, even though some have suggested that at an ideological or a conceptual level that there’s no more water to be had,” he said. “We think we can manage water more effectively and more efficiently with an improved system, one that is designed to be managed in an integrated way, as opposed to kind of a system that we have now that has evolved at a regional scale over time. If we add storage strategically and we operate it in an integrated way, we think we can generate significant additional water for all kinds of purposes. Ecosystems, fish, and wildlife are beneficiaries of this, and water supply, groundwater management, are all beneficiaries, and then the idea that we’re increasing resiliency and therefore able to meet this challenge of climate change.”
Mr. Bolland acknowledged that the study did not model climate change, noting that climate change modeling is rather complex, and the WSIP projects will have to do it on a project by project basis. “There’s going to be a lot more work to be done I guess on this question of what types of scenarios to model under changed conditions in the future, but there are some qualitative conclusions we can make about the result of this study as it relates to climate,” he said. “One of them is the biggest reservoir that we have in the state of California is shrinking, and it will be shrinking, it’s just a question of how much. The other conclusion that is a little more difficult is that a lot of that water may or may not continue to fall into the system as rain and come through in flashier flows earlier in the winters, and middle of the winters, and the question is do we have a system that can opportunistically use that water, capture that water and use that water, and the answer is that we don’t now, but we could.”
“This storage and conveyance approach can provide us the tools that we need to manage for those new challenges that we’ll be facing,” he said. “Of course there are a number of other related questions about water quality and water management related to climate change that do need to be addressed and can be addressed on a project by project basis; then part of this larger policy question is about how much emphasis to put into surface storage north of the Delta, south of the Delta, groundwater recharge and so forth, but we think this study does demonstrate the fact that additional flexibility has its benefits.”
During the discussion period, Vice Chair Susan Tatayon asked if any of the projects in the study should come online first in order to open the doorway to more flexibility in the future?
“There’s a serious answer and then there’s the joking answer,” said David Bolland. “I’ll say the joking answer first: these are all our children; none of them are better or smarter than the others, they are all equally important to us and we love them all. I say that jokingly, but that’s how we tried to manage this project is that we weren’t trying to sort or identify or hone in on how you could unpack the different kinds of attributes and the different kinds of projects in order to identify optimal projects or optimal operations. … Some people just really hate surface storage, period. Other people have a different view of that in that off-stream storage is okay, but on-stream storage is to be hated. We have a project suite here that includes some on-stream projects in some parts of the state and other off-stream projects in other parts of the state, and some existing projects that involve raising dams, at the margins increasing the size of the reservoirs, and then other ones that involve conjunctive management and developing groundwater banks and so forth. We wanted to focus on that diversity, we wanted to look at the value of the integration, but we purposely, frankly, steered clear of trying to identify winners and losers or prioritizations, and we are optimistic that the process that is going forward with the WSIP public benefits identification, has a lot of elements in terms of the applications that come in that will be used to sort through at least what the Water Commission thinks in the end is how California ought to think about investments in the public benefits side.”