City Council - workshop

The groundwater modeling of just the subbasins in the active management area. Let's see. So you will see, as I said, Dylan today. He's a senior hydrogeologist. He's a registered geologist. And I'll let him introduce himself more when his slides come up. And last, what's the city's role in all this? So we're like the layer that kind of keeps it all moving. We are gathering the data. We are moving it. We are checking things. That's our role. There's plenty of data that had to go forward to the consultants to get this work done. Okay, so our goals for the remainder of the year, the modeling and results analysis, infrastructure and results analysis, and then draft report writing. I highlighted the things in red today. Again, Dylan Easthouse with Matrix New World will be talking us through that first block, and Brian's going to take us through the last block. The timeline for the project, you know, the big red circle is what everybody wants to know. The draft report, it was decided December 2026 would be when that would be ready. And then, of course, the final report will be in July 2027 that's consistent with your strategic plan. Now we're gonna spend just a little bit of time on this slide. We talk about this project quite a bit in stair steps, but we also have landings too. So we're not at the bottom of the staircase. I don't know if that occurred to everybody, but when you look through the city's history, there has been report after report, effort after effort to maintain strong water supplies in the area. So you've climbed a lot of stairs already. What you are on right now is a landing. So you've been on a landing using the Assured Water Supply Program from 1999 to present, and you're going to keep using that, but it's time for, and there's many reasons for, why a long-term water management plan is appropriate and taking the next flight of stairs to get to where you're in a stronger position again. So your Assured Water Supply will be there, but long-term water management planning is going to advance you further. And once again, you know, of course there are many reasons, but it's also identified in your strategic plan, your 2026 to 2031. Moving along, just to see where we're at, sometimes these pictures help a lot because there's a lot of moving parts in this project. The supply and demand projections, you have been hearing about those for quite a while through your subcommittee, through your study sessions. We've had information sheets. And this was Herb's work for the most part. He needed to pull together all our supplies, our demands, project them. And then that data set has to go to two other consultants. And so one of them is your aquifer modeling team. So that's, again, going to be Matrix New World here today to talk you through the basics of that and to see where we're going. And then the other arrow dropping down is the demand management team.

Let's see.

Here we go.

This one.

Demand management modeling. So that is your infrastructure team, basically. They're going to take the supply and demand numbers and run them through some more paces for us. So this is where I'm going to go ahead and turn it over to Dylan. Again, he's coming in remotely because he wasn't, unfortunately, able to be here today. And I'm going to advance the slide to his, and then I'll just help him from up here. Dylan, can you hear us?

Yes, I can hear you fine. Can you hear me?

Yes, we can. Thank you, Dylan.

Okay.

Go ahead. Would you mind giving us a little bit of background of yourself? Sure. Thank you.

Sure. Sure. Yeah. My name is Dylan Easthouse. I'm a registered geologist in Arizona. I actually grew up in Prescott. Went to Miller Valley School. I've been doing hydrogeology now for 25 years. I have a house in Prescott. So don't let the matrix engineering scare you. We've been here a long time and we know the area. This is my backyard. So, and yeah, as Leslie pointed out, we're going to be providing the city with As far as long term management plan a summary description of the basic hydrogeology of the area and specifically of the city's well fields and and then performing the groundwater modeling. that is uh i'll get into a little bit more in a minute but the uh um it's really built upon what arizona department of water resources has made um for the area and we're utilizing that existing model to do the forward projections based upon herbs demand calculations so If it's all right with you, Leslie, I'll just dive into the basic geology of the area. This first slide that we made for you is sort of an overarching look at the surficial geology. And as we move forward, it might be easier for you to think about that the yellow area, the yellows, are alluvium, sort of sands and gravels, sands and gravels, clays, what you see on the surface out in most areas, except when you get into the higher elevations, you start to see the rocks, the pinks, the pink hues, and the purple hues that we'll get into a little bit in a bit, are the volcanic, so the thumb buttes, all the mesas, Those lava flows, those are what are lumped together as volcanics. And then the blues, the greens, and the browns, those are basement rocks. Those are the granites and the schists that you see on Granite Mountain, the delves. Those are generally mapped as greens and browns. So the city's wells are located in obviously the airport area and out in Chino Valley. This is part of a sub basin within the Prescott AMA and I'll discuss this a little bit more as we move forward with the slides. That's where all of the city water supply comes from, is from this little Chino sub-basin of the Prescott AMA. They have five wells in Chino Valley proper, and they have another three active wells in the airport area with a fourth planned for the future. Near the airport is also, if you're not familiar, the Prescott Recharge Facility on Granite Creek, where all of the Sundown Ranch effluent gets delivered there and recharged, as well as some surface water that is on Granite Creek. So I think we can go to the next. Oh, the total thickness of the aquifer. This would be something that we'll discuss a little more, too, in the next slide. The basin itself, and I say, I get a little bit technical here, and we call it a structural trough. That just means that there's faults on the edges of the basin that result in this being like a bathtub. I want to say that it is exactly like a bathtub, but it is a basin that is full of these sediments that we're showing here in this map. And the faults have formed that basin there on the edge of the basin, on the edge of the hard rock areas. And the thickness of those units is about 1,200 feet on average. There are some areas that are a little bit deeper, maybe up to 1,600, maybe 2,000 feet. We've not drilled deep enough to figure those areas out, but 1,200 feet is a pretty good number for the area of the airport well field and the Chino Valley well field. So, yeah, Leslie, we went to the cross section in the next slide. Can you set that up real quick?

So your cross section is from A to A prime. And so south, you know, this is the southern portion and this is the northern portion. So the next slide will have it's configured that way. So let me show you. Mr. Gilling has a question.

Oh, okay. Yeah. Hi, Dylan. Thanks for making this presentation. I have a little trouble following the 800-foot bottom contour. It looks like it goes through the Chino Valley Prescott Wells. Is that correct?

These contours, just a little background, these contours are based upon a geophysical survey that was conducted quite a long time ago and a surface geophysical survey. And so these are interpolated contours, not from wells or anything. They are interpolated from the different electrical properties of the soils. And so these are These are rough geometry of the basin.

Okay, that clears it up. Thank you.

You're welcome. And so I was going to point out that that cross section line, you could think of this line as essentially following 89 North to South. That's kind of how these wells line up from starting at Granite Dells approximately and going north to Del Rio Springs. And so yeah, if you think of Highway 89 traveling through there and that way we were able to capture the general shape of the Little Chino Subbasin where the city's wells are located. And going to that, yeah, this slide. So I remember I was pointing out that pinks, yellows and oranges are sands and gravels. and so we have those at the near the top of the cross section if you're not familiar with cross sections you can think of it as just like a slice of pie we've just sliced into the earth there along highway 89 straight down and then we're looking at it in profile the oranges and yellows are sand and gravels roughly speaking The purple and pink units are those volcanics that we talked about, the fumbus, the lava flows, okay? And pink and purple just signifies maybe a different source or a different chemistry, a different age. If you were all any of us for looking at them, they would all look pretty similar as lava flow and then under the lava is a little bit more sediment. It's just older sands and gravels above the green, which is, as I said before, that's really a schist in granite and sort of what we refer to as hydrogeologic bedrock. which for all intents and purposes is unsaturated. It doesn't mean it doesn't have water in it, but we don't consider it an aquifer. So getting a little into the hydrogeology here, the blue line about the center of that cross section represents the water table. And you can see the water table trends sort of left to right. which would be from South to North. It has a gradient of water. Groundwater is moving from area higher elevations at Granite Creek and the USF recharge up there to the North towards Del Rio Springs and. I couldn't think of a good way to show it on this cross section, but below that blue line. All of those sediments and rocks are quote unquote saturated. There is water present below that water table. And so that's why all of our wells that you can see that circle, those are the airport wells on the left and the Chino Valley wells on the right. They are all constructed down into those purple and pink units in the fully saturated part of the aquifer. And that's really the main part that we wanted to talk about with this figure. I will point out that I think it's easy to imagine sands and gravels as being saturated.

Excuse me, Dylan. Council Member Gamboge has a question.

Sure. You mentioned the north part. AND MADE REFERENCE TO DEL RIO SPRINGS. CAN YOU SHOW HOW THOSE TWO ARE CONNECTED?

I THINK, COUNCILMAN, THERE'S ANOTHER SLIDE THAT'S COMING UP THAT SHOWS HOW GROUNDWATER IS MOVING IN THE BASIN THAT I THINK WILL HIGHLIGHT THAT A LITTLE BETTER FOR YOU. I WILL POINT OUT THAT That the rock that comprises the volcanics that are the the pinks and purples in this groundwater is not found throughout that rock. It is found in fractures and in inner beds of the unit. So I think we can all imagine, you know, you can't squeeze water out of a rock. We have to find the areas of the volcanics that are fractured and broken up such that groundwater can move through there uh easily and so um but for all intensive purposes for our modeling and and uh how we consider this basin the eval mechanics are considered fully saturated um i just wanted to point that out um uh leslie i think we go to the next slide So this presents to you all the wells that Arizona Department of Water Resources monitors the water levels at and has been routinely or historically monitored water levels. And again, I'm just providing a basic hydrogeology discussion here. explanation of things and how we get the information we need for the model. But these wells, some of them are monitored more frequently than others. And the ones that have sort of the halo around them are monitored continuously and literally we could go online and see what that water level is today if you wanted to on some of these. As I pointed out before, the groundwater is moving in the aquifer from south to north. And we'll see that a little better when I show you the modeling slides in a couple. Depth of water is highly variable. Along Granite Mountain and the mint wash area, you've got water at tens of feet deep. As you move into the basin at the airport well field, it's 400 feet deep. So it's highly variable. But the elevation of it is something that these wells that ADW monitors allow us to get the shapes for the modeling purposes and to also track the changes to the water table in both the sands and gravels of the volcanics because those two aquifers behave very differently from one another, which we'll talk about a little bit more. I think that's all to discuss here, Leslie, unless you had something else. Yeah, so here we're getting into these. So pyrograph is just a fancy word for essentially showing water level, okay, and the history of water level.

Yes?

Jay, do you have a comment? I had a question.

It was actually on the previous graph. The water level rises about 100 to 150 feet just before you have the Krieger 644 foot. What would cause water level to rise there?

It's a very good question. Yeah, very good question. It's the same reason that Del Rio Springs exists, is that as water is moving through the basin and it gets underneath the volcanics, or maybe it even gets underneath some clay units that are in the upper alluvium, there is artesian pressure built. And that so what's happening with that rise in chima valley that you saw is that that is representative probably of water table in the lower volcanics and it's trying to get to ground surface and and these next hydrographs sort of highlight that point that those two aquifers are um behaving very differently from one another sometimes in the same location

the airport being one of those locations this hydrograph this hydrograph here shows excuse me yes remember Mary has a question thank you I'm sorry to keep bouncing you back but if you could go back to what is page 9 in your slide presentation the pie slice you didn't mention the two yellow lines that kind of track each other south to north across and in the explanation it indicates that it is the model layer bottom. What does that mean? Yes.

Yes, and we will get more into that and I'm sorry we have a lot to go over. The groundwater flow model that we'll discuss in more detail in a few slides is a simplification of the hydrogeology and in the Prescott AMA.

And- I'm sorry to interrupt, but if we're going to go into it in more detail on a later slide, I'm sorry to have short stopped you here. I can wait for the later slide.

No, it's okay. And we'll absolutely jump back to this when we're talking about that.

Thank you.

Yes. Yeah, so the hydrographs are provided here just for, again, for basic understanding of how we get to the groundwater model and how we're understanding the water table in the Little Chino. But these hydrographs here are water levels that were taken at those index wells that I pointed out. And if we were just, these are near the airport, matter of fact, this top one is right at the recharge facility. And you can see that the trend and the green dots are, well, there's two things unique about that. You see how the water table there is around 200 feet. You can also see that for the last 15 years or so, the water level in that well has been rising about two feet a year. And that is indicative of recharge that the city has been doing at their basements there. So the upper alluvial unit at the airport has been responding to all the water that is put into the ground there by rising the table up at that well in the alluvium. Conversely, at that same site, in the lower volcanics and a well that is 50 feet away from this one. There is a well installed that's only into the lower volcanics beneath the airport. It has had a decline, a decline of one feet a year. And that is because those two units behave very differently from one another. And they are responding to different stresses, the upper alluvium is responding to recharge the lower volcanic or is responding to pumping by the city wells and in proximity, so this. slide is really just demonstrating what Councilman you had asked about the water table in Chino Valley and that is these aquifers behave very differently from each other and when we are modeling the groundwater conditions, it has to account for that difference. This isn't just a simple bathtub. It's got multiple layers that have to be accounted for very differently. And they're very dramatically different, which we'll talk about in a minute. But Leslie, the next slide sort of highlights also the hydrographs for wells in the Chino Valley well field.

Before you go on, let me ask you a question. So looking at your basic hydrology chart, it looks like when we recharge, it just goes into the sandy alluvial layer. But we're pumping... the primordial glacier water from the cracked basalt that's like 500 million years old? Is that what I'm seeing here?

No, I don't think you could think of it in terms of age, Councilman. I think that there is communication between these two aquifers, by the way. It isn't that one is separate from the other. there's the upper one is leaking into the lower one uh we know that for a variety of reasons but it's just that the aquifer the lower volcanics is so much better at giving up its water to our wells that um it is you're seeing that difference um but the um But the age, I would be hesitant to tell you what the difference is in the ages there. But you're right. There is much younger water in the alluvium, especially underneath the recharge bases.

Okay. Thank you.

Yeah, also, I noticed in just after 2023, we have sort of our highest dot. And I'm assuming that's from the natural recharge or the very wet winter we had in the beginning of 2023. So is this particular well also very sensitive to the kind of precipitory events we have here?

Yeah, that is us. for artificial recharge at the USF. And so whether or not it was directly from natural recharge in Granite Creek or at the USF itself where the basins are connected to Granite Creek, you're right. That probably was a response to that. This is another hydrograph. These wells are in proximity to the cities wells in Chino Valley. I think 1 or 2 of them are actually city wells. I can't remember which ones, but. This I did want to point out that the upper alluvium in in Chino Valley doesn't have the recharge associated with it. So we don't see that dramatic rise. THAT WE SEE AT THE OTHER HYDROGRAPH, WELL, TWO FEET A YEAR. BUT THAT WILL THAT'S YELLOW AT THE TOP HERE. YOU CAN SEE THE WATER TABLE IS VERY SHALLOW. IT'S ABOUT 55 FEET. COUNCILMAN, THAT IS THE AREA THAT YOU WERE TALKING ABOUT THAT HAS THE BUMP IN THE WATER TABLE THERE. AND WE THINK THAT THAT'S ACTUALLY IN RESPONSE TO A DECLINE IN PUMPING in the upper alluvium. The majority of wells that are installed in upper alluvium are for domestic and stock water purposes. As you all know, irrigation out in Chino Valley has declined over the years. There's just not as many wells pumping from the upper alluvium, particularly in this area. And so we're seeing a small bump in the water table actually coming up in the alluvium out there. But the majority of pumping by, well, all of the pumping by the city wells and really any large irrigation wells that still exist comes from the lower volcanics in Chino Valley. And so you can see all of those are the remainder of these wells. Those are all declining at anywhere from 0.8 to 1.1 feet per year still. And so there's a a general trend of about a foot a year in the lower volcanic unit that has been very steady, very consistent for the last 15 years.

Excuse me, Dylan, I have a question. When you're talking about the water declining about roughly a foot a year, can you come up with how many acre feet that would be

over the surface of the uh of the aquifer the little chino do you can you put a number on that how many acre feet it's declining by um gosh i you know i i don't think i could put a number on it we've we've got a way to put um we've got this model um and i know that adwr does a an evaluation of um The amount of water and storage, or the amount of water that is recharging for the entire, but this study was really focused on the availability of water supply to the city and the city's wells. And so I can't really speak to what the. What the would be for the as a whole. Um, but maybe the, maybe the further explanation of the model and what we're, what we're trying to do with it will help answer that question.

Thank you. Um, uh, Mr Gary.

Has a question, thank you. Uh, Dylan. Some time ago, I spent quite a bit of time looking at the hydrographs for Prescott Gino Valley wells, 1 through 5. And those wells have been declining since 1949, and their rate of decline is quite a bit larger than the index wells is. I'm wondering if you could comment on that.

Well, certainly, Councilman, since 1949, if you look at the trend, it is much cheaper than this. But as that response to the aquifer for purposes of doing this projection period that we're doing the long-term management plan, the history of that pumping is really more important for purposes of calibrating the model, which we'll talk about in the next few slides. and the response of the aquifer to that pumping. There's a reason why those wells declined super fast in the 40s and 50s in response to irrigation pumping and municipal, but mainly irrigation. and why they have leveled off to, not leveled off, but become one foot a year instead of three or four feet a year. And we want to present the city with a reasonable projection of the future. And the history is important for calibrating the model for the future, but it's not appropriate for calculating the trend line for the future, if that makes sense. These trends for the last 15 years or so are consistent with groundwater use that we see the city having for the near term and for the long term, 50 years. And so it would be inappropriate to look at the trends from the 40s and 50s.

Okay, thank you.

HERE'S WHERE WE GET INTO THE MODEL. AND THIS IS GOING TO BE A BIT TECHNICAL. I'LL DO MY BEST TO TONE IT DOWN. BUT THE GROUND WATER FLOW MODEL FOR THE PRESKET AMA, AMA AS A WHOLE, AS A WATERSHED, IS SORT OF A MISNOMER. the active model domain, the domain that ADWR and all of us are really interested in is the pink line. And that pink line is the portion of the model that has at least 400 feet of alluvium and volcanics that represent the two primary aquifers. And so that model, can be further subdivided into two parts. It can be divided into the Little Chino Subbasin, which is everything north of 89A, excuse me, Little Chino Subbasin north of 89A, and then the Upper Agua Frida Subbasin, which is everything sort of south southeast of 89A, which is where most of the Prescott Valley wells are located. So it is a large domain, 250 square miles, but really it's not all of that. It's about half of that is that pink area. Each one of those model cells is a half mile square. It was and is constructed of two layers and we'll have another slide that explains what that means by layers. It gets back to that cross section question that Councilman had about what the yellow lines are on the cross section. But this model again constructed by AEWR is two layers, an upper alluvium and a lower volcanic unit. The model has There is groundwater present outside of this model domain. Okay. We all know and probably familiar with wells that are and, you know, that exists all along Granite Creek all the way into Prescott and same goes for east of Prescott Valley up along Menus Mountain. There is groundwater present in areas outside of this model domain. But again, this is a regional model that was built upon the idea of those areas don't have a physical supply of groundwater for 100 years or more, excuse me. And so that's why ADWR focused on this particular, these areas. And it really is back to that depth of bedrock contour that I showed you on the first slide. I think we can go to 14, Leslie. Yeah, so hopefully this maybe explains a little better about how this model is constructed, and that is that in the upper left hand corner we have a cartoon that shows essentially how the model is constructed and how groundwater moves through this area, and that is in the highest elevations, the mountains, there is precipitation that falls. That precipitation enters into the basin. It falls on hard rock primarily, enters into the basin. Some of it recharges down into, directly into, and some of it flows out along into the Granite Creek Secession and then into the basin through the creek system. As that groundwater gets into the alluvium, some of it, goes underneath the volcanics, or gets into the volcanics, and some of it stays on top of the volcanics. And that's where you get those differences in what we call head elevation, essentially those two units will end up, by the time you get to Chino Valley especially, they will have very different elevations where the water table wants to be stable. And Del Rio Springs used to flow at the surface. It still flows a little bit. But the head elevation of the volcanics is different than it is in the alluvium at the same location. This arrow on this map on the right shows how that groundwater is simulated to move in the model. Each one of those arrows is representative of a cell in the model and representative of how groundwater is moving horizontally in that cell. On the left hand side under bottom left, that is a cross section. It's another slice of pie. This one happens to be out by Del Rio Springs, where you can see that groundwater is not only moving horizontally on the right, but it's also moving vertically in the aquifer. It's moving down in some areas, it's moving up in other areas in response to pumping. or in response to a sort of uncorking if there's a well and that you've essentially released the pressure in the volcanics and suddenly all that water comes into the well and moves vertically. So, or fractures, fractures make. With respect to the difference in head.

With respect to where that connects to Del Rio Springs, I guess I got another question. Do you have an idea how much we would have to replenish the little Chino to refurbish? Del Rio Springs.

I do not get out. I'm sorry. That's not part of the long term management plan for the city. Yeah, it is. It could be something that I suppose that could be worked backwards, but I don't have an idea.

Excuse me, Dylan, I, I hate to do this, but, you know, we only have another 20 minutes left and we have some other speakers here. So if you wouldn't mind kind of giving us a little summary. I appreciate it.

You bet you bet Leslie what what were we missing left on the on the slides? think it's the uh oh the projections understand what's being added to the model or what's being modified to complete projections and a quick look at that next slide of products yes so the model will look at the herbs demands and we will assign that demand to the city's own supply wells We're also going to be adding in demands, assumed demands for all the other wells in the AMA within the model domain. And that includes all of the exempt pumping from domestic stocks in the upper alluvium and volcanics and irrigation pumping, an estimate of the future just to provide, just so that we're not, SO THAT WE'RE ACCOUNTING FOR ALL THOSE OTHER DEMANDS THAT WE KNOW ARE GOING TO GO AWAY IN THE FUTURE. AND SO, LESLIE, THE NEXT SLIDE SORT OF PRESENTS THE WHAT WE ARE ANTICIPATING WILL BE IN THE REPORT AND THAT IS A BASELINE CONDITION OF AQUIFER THICKNESS IN THE MODEL DOMAIN AND SHOWING, YOU KNOW, HOW MUCH WATER IS LEFT OVER STARTING IN 2024 AND THEN Leslie, the next slide describes the difference, and I'm sorry we couldn't show you those today, but essentially each well field will get its own map of 10-, 25-, and 50-year change in saturated thickness within the well field. And it will be accompanied by, obviously, a description, a verbal description of and a table of what that changed. That's really the basis of our report. At the moment, we have approximately 450 feet of aquifer remaining in each wellfield. And the 50-year simulation, give or take, is 80 feet in Chima Valley and about 40 feet in the airport. Give or take, don't hold me to those numbers, but the less decline in the airport will feel obviously in response to recharge, but also there is less pumping at the left field, so. I think that's it, Leslie.

Okay, well, thank you very much, Dylan. What I'd like to comment on is it doesn't really matter how much water is in the ground because we've been adjudicated legally and we have caps on how much we can pump from the Little Chino and also from the Big Chino, so I think we need to Consider that and include that in these in these studies because we could have like a trillion gallons underneath us and But we can't legally Pump it because we have caps. Is that correct?

That's a pretty big question right there so we have supplies identified in the in the city's assured water supply and You, as a community, go back every 15 years or when the state decides to reshow what's happening out there. And those numbers can go up or down. So I would generally say those are the numbers that we are tied to right now. In the future, those numbers could change up or down. MS.

Thank you.

Let me move to slide five really quick. This was just to give you an understanding that there's a technical memo number five related to the big Chino. It will not have a modeling component to it. And then from there, it's Ryan would like to share this kind of the report framework, a little more discussion if you have time.

Thank you, Dylan.

Hello, Mayor and Council. Brian Reese, Water Resources Manager for the City of Prescott here. So, yes, I wanted to, now that we talked about the groundwater modeling efforts within this study, I wanted to go ahead and kind of bring this all together so we can see how these modeling efforts will help out with our long-term water management planning. So on this slide here on the left, we're talking about supply and demand analysis. And we've talked to you before about this, and this is the work that we're doing with HERB and trying to establish all our legal supplies and getting to the mayor's question on what supplies and what water we have legally are able to tap and utilize. There's a distinction between the physical water supply that's available and the legal water supply that's available. And they're a combination of water rights that the city has and are entitled to use. And it's a combination of rules and regulations that we are obligated to work within under the Assured Water Supply by Arizona Department of Water Resources. So our our specialized consultant, Herb, looks at those aspects of separating the physical water supply or at least acknowledging the portion of the physical water supply that is legal supply. And that's what we utilize within our supply and demand analysis. We have to get that right because we're making projections and we're trying to do some long-term planning on this. So we need to know what those supplies are. So yes, 100% it is applicable to this study.

I just want to mention the reason why we have these caps is to protect the flow of the Verde River because Salt River Project has the surface water rights and they depend on that water to supply water to the Valley and they also have groundwater that they can pump and they have CAP water and recently their CAP water allocation has been reduced and they're going to want to increase groundwater pumping and want more surface water delivered so we're I can't see those caps being increased on us

Well, like you just talked about there, it's a complicated mix of water rights of 100 year supply through the groundwater legislation that led to shared water supply program and taking all of those things into account. We have to put together the best plan for our supplies so that we can move forward in the future. The city has to fight for supply. It always has to fight for supply. You have to have the vision to go out there and get supply. But just by getting it and having a water rights certificate doesn't always mean that you're not going to end up in court to defend those rights. It's part of water management. So, yes, so the legal supplies is that aspect of it. We're looking at all of our demands existing, our committed demands, those that we have in commitments and agreements and agreements. water contracts. We're looking at all of the potential support services that we need over a planning period. And in this case, that planning period is 50 years, but we're looking at also 10 year and 25 year increments within that 50 year period. Putting all that together, we take those demands and we project them in that 10, 25, and 50 year period. along with our supplies, that creates our water budget. We can look at the water supplies that we say we have legally and that we're gonna count on, and we look at those demands that we're projecting out, and how do they compare? How much of flexibility do we have between the supply and the demand? How much buffer or safety factor do we have between them? So that's what we're showing on the left there. Groundwater modeling as Dylan and Leslie just went over is how we take and we can take those projected demands, convert them into imprint, bring them into the model and see how the aquifer reacts to them based on those pumping rates. That's how we put those demands into the model. And that's how we can see how that aquifer is gonna respond over that same 10, 25 and 50 year period. And then that creates another part of the picture for us. So on the left hand side, it tells us, do we have enough water? Do we have enough water to grow and to be the community that we envision over the next 50 year period? And then the right hand of it tells us, But if we use that water, how does the aquifer react to it? And with both of those things together, that's where we can get that more complete picture of the water over that 50-year period. And that provides us that very powerful tool that we can use to make the decisions that we want to make from this plant. So on this slide, I wanted to just go over the plan components a bit. We're talking to Dylan about the hydrology and modeling. That's gonna be one of our technical memorandums that's being produced for this planning effort. We have technical memorandums covering the city's baseline conditions, The water demand projections, that's all those demands and leading up to the projections we just talked about. Our water demand practices, so what has the city been doing? What do we do from a conservation aspect? Everything from our codes that talk about landscape and about how we restrict water use at certain times of day, all the way to our rebate program incentives that we use. So we compile all of that information. together, the hydrology and the modeling. There's a Big Chinos sub-basin study that just does, it just lets everybody, it's just there to understand that we have this additional water supply, we're not using it at this point in time. But the point is, is that we have all these technical memorandums that will be provided to Corolla so that they can incorporate all that information and start creating the analysis and figuring out in the plan, what are our best ways of moving forward for water supply. Those technical memorandums are help completed by our consultants, but there's a humongous amount of work that went into them with the employees from the city. Those people have the expertise and understanding of how water management is done in the city, water policy, We have to extrapolate all that data from that and we have to give it to the consultant for them to use. On the water operation side, how our infrastructure is managed, where our infrastructure is, all the information and data we have about repairs and the conditions, all of that given to Corolla through these five technical memorandums. Corolla's then gonna take all of that information and they're gonna create a base plan for us. And it's kind of divided into these four major chapters. So chapter one starts off and it's basically executive summary and introduction, creates the physical setting, regulatory environment obligations, our rate structure, water uses. Basically, this is gonna give the clear picture of what the current situation for the city's water situation is right now. So that's what we're starting off of. Chapter two runs into those flow projection demands, given all of that information that Herb and Leslie helped create. Give it over to Corollo, and they're using the basic objective of trying to figure out strategies and recommendations that will defer the cost of major additional water infrastructure. through the use or through the concept of reduced losses on the infrastructure and what the city can do to reduce losses on their end and providing more efficient uses by our customers. So that demand, these are all the demand management strategies. So to take the data, they're gonna give us an idea of how we can take all of the things that we're doing and increase them or increase the impact of what we're doing so that we can defer the cost of having to do additional major infrastructure. Madam Mayor.

Yes, Ted.

A couple questions, Brian, and we can use any scale you want, acre, feet, or feet. From this analysis, do we know how many acre, feet are in the Little Geno?

I do not think we have a, we have some rule of thumb values from reference studies and things. From this particular study, I don't think we've quantified the amount of water in the little genome aquifer.

Do we know, okay, let's change the scale. Do we know how many feet are left in the little genome aquifer?

Same answer. We don't know. Yeah, we're looking at things from the city's standpoint and from a supply and demand analysis based on the legal water supplies that the city's had, the projections of what they think their demands are going to be, and how those things change from year to year. 6,500 to 7,000 acre feet per year is probably the last five years of usage or so. That we use, huh?

Yeah.

Or that we pump.

So earlier when you talked about supply and demand analysis, you know what demand is.

Yes, we do. We have an understanding of demand from our existing users from the pumping, and then we have an understanding of demand because we know what commitments we've made through contractual obligations.

So I asked you a couple questions about supply. How are you going to do a supply-demand analysis knowing demand and not knowing supply?

Well, we know... We will know our supply too. We break it down into our assured water supply that we have from our groundwater. We can make estimates on how much effluent return we get from our sewers, treat, and we can recharge, and we can also use that water for non-potable uses. And then we make evaluation of how much surface water on average we can get every year. And that makes up the bulk of our supply.

Excuse me. It's five minutes to three. This has been a very engaging study session, and I think we need to continue with another one. And because, unfortunately, we could talk about this all day. But I have just one question before costing.

Yeah, definitely. So we obtained a $40,000 USBR federal grant in order to defer some of the cost of this. To get us to a July 27th final report, we're looking at $245,000 worth of work to get us to that point. That 40,000 will defer some of that cost. And then when we, and at another study session, when we can discuss a little bit more about the work in the future, additional water supplies, we haven't scoped it out yet, but we, you know, we're gonna estimate between 200 and $300,000 to give us an understanding of major additional water supplies and how that will work out or what would how that works into future supplies for the city. So together we're looking at four to $500,000 for the long-term planning efforts. I looked up to see our water fund, which is made out of our water budget for our water and our wastewater is about a little over 38.5 million. So what that comes out to is about one to 1.2% of our annual water budget is what we're using for our long-term water management planning.

Okay, unfortunately, time has run out, and we'll make an effort to have a second meeting with the rest of this information. This meeting is adjourned. Thank you.