Clay Sellers: Got questions about the Brazos. No more unknowns. Ever wonder where that water comes from or where it goes? We're Unpacking the Brazos River.
Charlie L Shugart: Welcome back to Unpacking the Brazos River. I've convinced the Brazos River Authority's water service manager, Aaron Abel, and lead hydrologist, Chris Higgins, to return for another episode because we took one too many side quests during the last episode, and we didn't finish our main mission. So, here's part two. If you're listening out of order, you might want to go back one or don't. Live your best life. Chaos is a valid choice. Welcome back, guys.
Aaron Abel: How are you doing?
Charlie L Shugart: I'm good. I'm so glad you guys were willing to come back.
Aaron Abel: Absolutely.
Chris Higgins: Yeah. Thanks for having us.
Charlie L Shugart: So, we're just going to dive right back into where we left off. We talked about how many reservoirs there are in the state and the Brazos River Basin. We talked about the different types of reservoirs being water supply, flood control, and in Whitney's case, a multipurpose reservoir because it also includes hydropower. And while we talked extensively about water supply reservoirs and a whole bunch of other things, we didn't get to flood control reservoirs. So, with that in mind, what is a flood control reservoir? What does that look like?
Chris Higgins: In general terms, a flood control reservoir is a reservoir that has a flood pool, which can store two to four times the amount of water that it typically has in conservation pool. And the conservation pool is generally like when you see the lake is full, that means the reservoir is at the top of conservation. It's a full lake. I'll give you an example, like Lake Whitney stores over 600,000-acre feet in its conservation pool, but it can hold up to an additional 1,400,000-acre feet of water during a flood event and hold that back. Back to the general description, these flood reservoirs store water during the flood, and they attenuate it over time. They release it over time to reduce downstream flooding.
Aaron Abel: Within these flood control reservoirs, when they enter a flood event, you know, it may be at top of conservation. So, the flood control pool volume, that two to four times the volume of the water supply, is available for inflows to enter the reservoir and the lake level to rise and rise greatly. Like, sometimes, you know, we'll see 20 to 30 foot rises in these reservoirs during flood events. And the Corps, when they plan these reservoirs and BRA was part of that planning process, we actually provided funding for the actual capital improvement at some of these dams. So, we are a part of the flood control aspect through that. But in the planning of those reservoirs, the Corps actually purchased a lot more land that allows them to inundate a lot more property than the BRA reservoirs can. Because all of our reservoirs have property owners right up to the shoreline in a lot of times.
Charlie L Shugart: So, when we talk about inundations, you're talking about, like, the parks, the literal property that surrounds the lake.
Aaron Abel: Yes.
Charlie L Shugart: Okay. And that they can basically flood?
Aaron Abel: They can flood, you know, at Lake Waco or Lake Whitney. It was, I guess, in 2021 and in 2007 and 2015 to, you know, 2017, those were all wet years in the spring and in in parts of the summer. And a lot of the recreational facilities were out of service because they were underwater. And the flood control reservoirs were doing their job by capturing that floodwater and preventing that water from going downstream. If those reservoirs weren't in place, downtown Waco would be inundated in certain flood events. You know, the lower portion of the basin in Fort Bend County, there's over 800,000 people that live in Fort Bend County that live behind levees and are protected by levees. The flood control reservoirs are extremely important as well for a different reason - to mitigate those impacts. So, at the end of a flood event, Lake Whitney or Lake Waco or Lake Belton, you know, they may be twenty, thirty feet above top of conservation. But all the rain has passed, the flows in the river downstream have lessened, and the Corps makes decisions on how to release that two to four times the volume of the water supply that's stored in the flood control to release slowly over the course of sometimes up to two to three months or more depending on, you know, if it rains on top of reservoirs that already have water that's stored in the flood control pool. So, it's very, very different.
Charlie L Shugart: Yeah.
Aaron Abel: And it's essentially contrary to what water supply is. Water supply wants the reservoirs as full as possible at the end of a wet period. Flood control reservoirs, they would like to have all their flood control pool completely evacuated to prepare for the next flood.
Charlie L Shugart: When you say top of conservation, is that an imaginary line?
Chris Higgins: No. It's defined, it's usually based on mean sea level, elevation from mean sea level.
Charlie L Shugart: Yeah. I guess I don't mean it's imaginary. I guess I mean, is it, it's not like if you're looking at the lake and it looks full, does that mean it's top of conservation?
Chris Higgins: No. They'll have lake elevation gages and then also staff gages. And so, there's a specific defined elevation for top of conservation at each reservoir.
Charlie L Shugart: Okay.
Aaron Abel: For our three reservoirs or at least some of our reservoirs, BRA reservoirs, we have operational full levels. And operational full levels are not necessarily top of conservation. If it looks full, it may be close to conservation, but it may be the operational full level.
Chris Higgins: Because we don't have a flood pool, if we kept our reservoir at the very top of the gates, if you went out there and you look at the reservoir level and you looked at where it was on the gate and it was at the very top, we wouldn't have any time to react to any type of flood event. As soon as there was additional inflow, it would begin overtopping over our gates. So, we have to build in a cushion.
Charlie L Shugart: Right.
Chris Higgins: In order to manage our lake safely and effectively. And so that's why we have these operational full levels.
Aaron Abel: Yeah. So, at Lake Granbury, you know, we only have about three inches of vacant storage when it's operationally full.
Charlie L Shugart: Gosh. That doesn't feel like a lot.
Aaron Abel: Yeah. Between the operational full level and the top of the gates. At Possum Kingdom, we call our operational full level at elevation 999, Top of the gates, and the emergency spillway is at elevation 1,000, so we have a one-foot buffer. And sometimes at large flood events, the lake level will get above 999. Conversely, at Lake Limestone, those gates were designed such that the top of the gates are actually two feet above the top of conservation. So even if the lake level is at top of conservation, we still have what's called a two-foot surcharge to temporarily store water during large flood events. I know we have some educational videos out there that explain this in more detail, but I think we've gone down a rabbit hole a little bit, but that's fine.
Charlie L Shugart: So, is what we have, like, our three, Possum Kingdom, Lake Granbury, and Lake Limestone, is them being water supply a permanent thing? Could it ever be, like, reprogrammed or restructured to also act as flood control?
Aaron Abel: No.
Charlie L Shugart: Why?
Aaron Abel: Every bit of water that is stored in the reservoirs, and when I say every bit, all the water that is stored below the top of conservation levels, we have water rights through TCEQ. So, the water that you see in the river and the reservoir is held in trust for the people of Texas with TCEQ, and we have entities like BRA and others that go to TCEQ and permit to use that water. We have contracted the water that is under our water rights. So, if we were to change or some people call reallocate from water supply to flood control, that would essentially lessen the amount of water that we can provide, and those contracts would be null and void. So, we cannot, just at the whim, change from water supply to flood control. Legally and structurally and operationally, we just can't do that.
Chris Higgins: When you originally design a reservoir, you choose your location based on what you need that reservoir for. The terrain has a big part in selecting where you construct these reservoirs and then where you set the top of conservation pools and the different pool levels.
Aaron Abel: The reason why we can't convert from water supply to flood control is we don't own the land that would be able to be used for flood control. And, of course, the dam has to be completely reconfigured, so that's cost-prohibitive. But even if you could do that, there's private property that is owned from the top of conservation upwards. BRA does not have the authority to inundate certain parts of the land around the reservoirs that are already owned by private citizens.
Charlie L Shugart: We're not going to intentionally flood people's homes to make it a flood control reservoir.
Aaron Abel: Yeah.
Charlie L Shugart: Yeah. I mean, that makes sense. So, we can't go up. We can't go out. Why can't we go down? Can we not dig out the bottom?
Aaron Abel: Oh, very good question.
Charlie L Shugart: Of a lake and make it deeper.
Aaron Abel: That question comes up all the time. And what you're talking about is dredging. And we've looked at that. Many of our customers in certain areas of the system have asked the same question. It's like, well, you know, it appears like there's so much mud and silt that is flowing into the reservoir. Can't we just dig it out and recoup the volume that was lost through sedimentation? So, sedimentation occurs in all reservoirs and, you know, what happens, you know, once you construct the dam and you have run off, you can see the muddy Brazos, you know, it can be full of silt sometimes and in mud. And that water will flow into a reservoir and then the silt settles out. And so, you have a loss of volume due to sediment load, and that does happen. It's cost-prohibitive because it takes so much diesel, and there's permitting involved. What do you do with the silt? How do you transport it, or do you transport it? And we've looked at the cost. And, you know, data collected over the last several years, we've seen costs of upwards of 25 to almost a $100,000 per one acre foot. In many of the reservoirs over the life of a reservoir, say for instance, you know, at Possum Kingdom, when it was first planned and developed back in the mid to late thirties, we thought we could store about roughly 720,000-acre feet of water. We've done surveys over the years, but some of the more recent surveys, you know, suggest that there's only about, you know, a little over 500,000-acre feet of water stored. Part of that could be the uncertainty in the in the technology of determining volume of reservoirs back then, but part of it is sedimentation. And so, you're talking about tens of thousands of acre feet, and that's just the storage amount that you could remove, but that doesn't equate to, you know, how much water you can actually use based on the recovered storage. And so, it's really cost-prohibitive to go down that route. You know, there are certain areas in the country, I know at Kansas, they have some reservoirs and some sediment control projects where they're actually, they're releasing the sediment downstream. If you can stir up the sediment, you could release it downstream. There are some pretty major environmental impacts to that, but nothing has been talked about like that in Texas, to my knowledge.
Chris Higgins: They've had some dredging projects, but they're very small bodies of water. They're not these, what we called earlier in the podcast, big waters
Charlie L Shugart: Big Waters
Chris Higgins: I think there's a small reservoir in in San Angelo. The whole reservoir was about three feet. You could walk out in the middle of the reservoir and just stand there, but it's a small, like, terminal storage top reservoir.
Aaron Abel: There have been several reservoirs where, over the years, we've noticed some increased sedimentation. We've done some studies, you know, determined that, well, there's been some land use changes or there could be land use changes to prevent the sedimentation. So, it kind of depends on the future. You know, right now, we don't have any reservoirs that we're monitoring that show significant sedimentation, above and beyond what has been considered normal.
Charlie L Shugart: Oh, okay.
Aaron Abel: But again, like Chris said, what we're talking about is big water, big reservoirs, not your stock tanks or not your smaller reservoirs that dredging could be feasible on a much smaller level.
Charlie L Shugart: Yeah.
Chris Higgins: So roughly every ten to fifteen years, we have a volumetric survey performed on our reservoirs. And so, we can compare past volumetric surveys and be able to make an assessment of the amount and volume of sediment that has been deposited in our reservoirs over that time. And it'll give us a good idea of what the sediment rate is. And it can vary because one big, large storm can bring in a lot of sediment. So, it depends on, you know, the magnitude and then the number of large storm events that you've had over time. So, we make this determination on, like, an average annual sediment rate, so we can do future projections and plan for that. And like Aaron said, none of our reservoirs, what we're seeing, have a significant sedimentation issue. We've seen changes over time. Lake Granger used to have a pretty high sedimentation rate, but I think that was a result of land use changes. They used to have a lot of row crops and farming up in the watershed of Lake Granger, and I think there's been a lot of development over the years. And so, you know, you've seen a reduced sed-rate Into Lake Granger.
Charlie L Shugart: Yeah. And let's go back to the water supply a little bit. We talked a little earlier about if I was super downstream or in the lower part of the basin and I needed water and there wasn't water in the river, I would reach out to us and say, send me water. If we're working with our water supply system of reservoirs, which is our three and the eight US Army Corps of Engineer reservoirs, how do we decide who is sending me water downstream?
Chris Higgins: I can take a stab at that one, Charlie. This is one of those topics, like some of these others, where we could spend this whole podcast on. Well, I actually, for like this one, we could do a whole series of podcasts.
Aaron Abel: I don't think she's gonna invite us back, Chris.
Chris Higgins: I'll try to summarize it as best as I can. We have 11 reservoirs in our water supply system, as we stated. The biggest driver in our water supply release decisions is our lower basin customers and their demands and their need for water. So, when the streamflow in the lower basin gets down to a level where they physically can't divert the water, where their pumps will start cavitating, where they can't take the water, they need to augment that stream flow with releases of stored water. And so, the call is made by our customers. They have eyes on the ground. They have the contracts with BRA for that water. They make the call on the water. BRA doesn't make that decision. And another large component of managing the Brazos Basin and its water supply system is the Brazos Watermaster. So, the Brazos Watermaster is involved, our lower basin customers are involved, and BRA is involved. And we have frequent meetings with that group to assess conditions and make determinations on the need for water supply releases throughout the year. Even when it's wet, we maintain a relationship with those guys, with those customers and the Watermaster. When we get to that point, number one, there's several reservoirs in our system that we would never use, that we would never release water from because they're smaller reservoirs and they have high local demand, and we use those reservoirs predominantly for that local demand. And so, you got Lakes Aquilla, Granger, Lake Georgetown, and Lake Proctor. Those are kind of four reservoirs you can kind of take out of the BRA water supply system of 11 reservoirs. The other major component of it is - what is the current climate? What are the conditions in the basin? Is one part of the basin experiencing a drought and the other is not? But with the Brazos Basin being so large at 42,000 square miles, roughly the same size as the state of Tennessee, and that's kind of a luxury for the BRA. With having such a large drainage basin, it kind of has built in drought resiliency. So, you can be experiencing drought in one part of the basin, where you're not in other parts of the basin. A good example is that this is the last drought. The 2022- 2023 drought was a pretty severe drought, but that impacted the Little River Basin. The upper part of the basin, the main stem with Granbury, Possum Kingdom, and Whitney, those lakes fared fairly well through that drought. It allows us to leverage the wetter parts of the basin. And we're also looking at multiple other factors. We're looking at intake elevations for our lakeside customers. We're looking at the implementation of our Drought Contingency Plan, which part of the System is in some level of drought stage or is in the worst level of drought stage. We're looking at firm yields. A firm yield is just, you know, the reliable supply of that reservoir, and we take into account the local demand. So, BRA, when we're looking at this, we're ensuring that when we do release stored water from a reservoir, that we are also going to be able to supply those local demands and get through this drought. So, when we start making decisions on which reservoirs to release from and how much, all those factors are considered. Typically, what we'll do is leverage Lake Whitney and Lake Sommerville. We have one customer in Lake Sommerville. It's a fairly large reservoir. Lake Whitney, we have essentially no local demand. There's one lakeside customer. It's a very small customer. We'll use those reservoirs first. And then, as we propagate through the drought, we have modeling tools. We have forecasting tools that we're constantly running. We're constantly looking at the impacts to our reservoirs of making these downstream water supply releases, essentially trying to optimize the system. We're trying to manage it the most effectively, be able to efficiently and effectively supply all of our customer base with the water that's under contract, you know, throughout the basin. And so, there's a lot of decisions, a lot of factors, and it's not just one person. You know, we'll go in and draw up scenarios, then we'll get together, and we'll bounce these ideas off, and we come up with a plan. And the plan is constantly being adapted, and it's constantly being adjusted, and Mother Nature is a big driver in that. That's pretty much the process like in a nutshell. To be able to sit down and really explain it, like I said, would take some time. But I think that kind of captures the essence of how we manage our Water Supply System during droughts.
Charlie L Shugart: Yeah. No. I thought it was a good recap.
Aaron Abel: Yeah. The Brazos Watermaster program is a program within the Texas Commission on Environmental Quality. That program manages the diversions and all the constraints that are within everyone's water rights. So not just BRA's water right, but all the other water rights from Possum Kingdom all the way down to the coast. That program was implemented in 2015, but we coordinate really, really closely, as Chris said, with both the Brazos Watermaster staff and our customers in the Lower Basin, specifically for the releases and demands that are associated with that part of the basin. Now we also coordinate with other customers throughout the basin as well. And as Chris said, Lake Proctor is an area that is different than, you know, Lake Aquila. So, Lake Proctor, we have a group of 20 to 25 farmers that are immediately downstream, and we release water for them. We have lakeside customers at Proctor. At Lake Aquila, we have other customers that divert directly from the reservoir. So, all of the use of our water gets funneled through the Watermaster.
Chris Higgins: They're the final say in how the water resources in the Brazos Basin gets utilized among the water rights and the BRA contracts.
Aaron Abel: They're the regulatory entity that oversees the water rights within the basin, including the BRA.
Charlie L Shugart: So, it's during these conversations that we would tell the US Army Corps of Engineers, for instance, hey, we need you to release water from Lake Whitney downstream.
Chris Higgins: When our lower Basin customers and the watermaster determine what the needed magnitude of release is going to be. We determine which reservoir to release it from and how much, because we also have to account for channel losses. So, if they request, say, a 100, we have to release more than a 100 to account for the water that's gonna be lost when it's released from the lake down to their diversion point.
Charlie L Shugart: Wait. Why is water being lost?
Chris Higgins: For a multitude of reasons. You have evaporative losses. You have vegetation that's sucking up water. You have, bank storage losses. And there's also riparian rights, domestic and livestock, so there's smaller diverters that have superior rights, senior rights to that water. There are various different reasons why you're gonna experience channel losses. When our Lower Basin customers make a call for water, we determine the magnitude and the timing of that release, and we determine which reservoir that we're going to release from, kind of based on that whole scenario that I just went through.
Charlie L Shugart: So, we have people taking water who are living right next to the lake. We have those who are 40 miles from a lake. We have those immediately downstream of a lake. How are we, I don't know, keeping receipts? Like, how are we tracking every gallon that gets pulled out of the river by a city or factory?
Chris Higgins: It's changed over time. Before the Watermaster program was established in June 2015, our customers', their water reporting was defined in their water supply agreements with the BRA. The customers would have to report, all the customers, up and down the basin would have to report how much they used by the 15th of the following month. Now it's a lot more complicated post Watermaster. Our lakeside customers still report in that manner, but our lakeside customers, we're in constant coordination with them because they have to provide estimates of what they're gonna divert, and then they have to provide what they actually diverted within seven to fourteen days after they diverted it. We're constantly getting these water reports from our downstream customers. We have to manage them a little bit differently because they're co-mingled with other water rights in the basin. And so, in order for the Watermaster to be able to effectively manage the water supply system, they need to know who's taking water and when. So senior water rights and downstream water rights aren't impacted and impaired. And so that's kind of the main function of the Watermaster program is to manage those contracts and water rights and make sure that we're abiding by the prior appropriation system. The first in time, first in right, and the water right holders are getting the water that's afforded to them through their water rights.
Charlie L Shugart: Yeah. Okay.
Aaron Abel: You mentioned receipts. We probably take multiple receipts almost every hour.
Chris Higgins: Yeah.
Aaron Abel: We have multiple tools that are required for the Watermaster process and, you know, it's basically data management. We convey, like Chris said, all the projections and all the estimates and the actual use. And then the Watermaster takes that information, and they have their own Watermaster database that they use to track and document. So, there's a lot of data management, a lot of phone calls, and a lot of emails. As Chris said, it's gotten way more complicated over the years, and it'll continue to be more and get more complicated over the years.
Charlie L Shugart: Is that good that it's getting more complicated?
Chris Higgins: It has its positives, definitely. I mean, our system is being looked at under a microscope now when before it wasn't. They have boots on the ground. The Watermaster is a team. It's a group of people, like Aaron said, under the umbrella of TCEQ. They have, you know, the Watermaster and the Watermaster Deputy, but they also have the field deputies that go out and have boots on the ground that are checking meters, making sure there are no illegal diverters. The efficiency of managing our water supply system has probably improved under the Watermaster.
Charlie L Shugart: Yeah.
Chris Higgins: When there are illegal diverters or when there are circumstances where there's a dispute over whether someone should be diverting or not diverting, now we have someone in our basin that can come in and manage those resources, and I think it's positive.
Charlie L Shugart: Well, you mentioned, you know, that this puts more of a microscope on the water supply in the Brazos River Basin, and, you know, I feel like that has a negative connotation. But the problem is, the reality is that we have this huge population increase that is continuing to happen across the basin. And if we're not monitoring every little bit of water that's happening out there, how do we not better ensure that everyone's getting the water that they need and are depending on for them for their day-to-day stuff? So yeah. No. I could see how that would be really important.
Chris Higgins: Yep.
Charlie L Shugart: Have the BRA and the US Army Corps of Engineers always worked together in this capacity?
Aaron Abel: Yeah. Chris and I have only been here, you know, eighteen to twenty years. But, obviously, over the course of that time, we've had a very close relationship with the Fort Worth District Army Corps of Engineers. The Corps of Engineers is divided among districts, divisions, and then the headquarters, which is in Washington. But, you know, we work with the Fort Worth District. You know, honestly, I think with our development of Possum Kingdom in the late thirties and early forties, there were conversations between BRA and the Corps of Engineers then. They were in the midst of planning Lake Whitney at that time. And Lake Whitney was the first Corps reservoir to be constructed. And my understanding is that we've had a good relationship with the Corps for almost ninety years.
Charlie L Shgugart: Yeah. Yeah.
Chris Higgins: And you almost have to. I mean, because eight of our reservoirs in the BRA Water Supply System are Corps reservoirs. We share reservoir data daily with them. We have for, and I don't know how long that goes back. They collect all their releases and evaporative losses and inflows into their reservoirs, which is an important component and data that we need to be able to manage our system effectively, and we share our data with them.
Charlie L Shugart: Yeah.
Chris Higgins: And so, it's more than just requests and releases. We pay O&M (operation and maintenance) for those eight reservoirs.
Charlie L Shugart: Okay.
Chris Higgins: And so, we meet frequently. They give us updates on projects and repairs to their dams and dam structures because those impact us. There's very close coordination with the BRA and the Corps on multiple different levels.
Charlie L Shugart: Yeah. You know, earlier, we talked a little bit about the lake levels fluctuating, whether it's in drought or during rainy season. Does this mean there's no such thing as a lake that stays at the same level all the time?
Chris Higgins: There may be what you consider constant level lakes in certain areas, but not in the Brazos Basin. There are no constant-level lakes in the Brazos Basin. And there was a big misconception with Lake Granbury for years because we did have hydropower at Lake Possum Kingdom all the way up until 2007. Those hydropower releases helped keep and maintain Lake Granbury at a fairly constant level, although it fluctuated some, but it never was a constant level lake. In order to have a constant level lake, you would have to have a large water supply upstream of your reservoir, which, in some cases, we do, but these are water supply reservoirs. They were built and intended for water supply. You know, I don't want to get kind of off track, but LCRA, they've been mistaken for having constant level lakes. But, no, the Brazos River Basin does not have any constant level lakes and never has and never will.
Charlie L Shugart: Okay. We've talked about a lot. Is there anything that we've left out that you guys, you know, feel is really important for people to know about water supply reservoirs, flood control reservoirs, or just …
Aaron Abel: I think this podcast, I know there's twists and turns to this podcast, but it gives, I think, it'll give the listener a really good idea of, I mentioned this before, how I wouldn't say complicated, but how much communication, how much coordination, and how much effort it takes for raw water stored in a in a BRA reservoir or flowing down the river to get to your faucet.
Charlie L Shugart: Yeah.
Aaron Abel: Hopefully folks will tune in.
Charlie L Shugart: It's got a lot of really good information.
Chris Higgins: You know, there's a whole lot that we didn't have time to really fit in or discuss, and kind of the things that we do, the other things that we do to help maintain and manage the BRA Water Supply System.
Charlie L Shugart: Oh, I've made a list. I've mentioned, like, three or four different things that I was like, this might be good individual podcast episodes.
Aaron Abel: Yeah.
Chris Higgins: Yeah. And we didn't even get into our System Operations Permit. And the level of staff effort, in maintaining
Aaron Abel: Yeah.
Chris Higgins: The water accounting plan, and as Aaron said, coordination, and coordination with your department, Charlie, with the public information office, and all the questions that y'all field to help keep the BRA transparent. And we're not hiding anything. We lay everything out on the table, and you can pick up what you can, what you want to, leave it on the table, ask us anything, and we'll give you a straightforward answer. So and so, I appreciate what your department does too in getting this message out and the other ways that y'all get information out to the public. So, thank you, Charlie, for having us.
Charlie L Shugart: Yeah. No. I appreciate you guys both for coming on and being a part of this. It's easy to look at receding shorelines and think the world is ending, but a dropping lake level isn't a failure. It's the sound of a system doing exactly what we built it to do, keeping the lights on and the taps running when the Texas sun is trying its best to bake us into a crisp. The Brazos is a wild, moody stretch of water, and we're just the ones lucky enough to borrow a sip. Next time you're out on a boat, take a second to look at that dam. It's not just a wall. It's the reason we're all still here. Catch you next time on Unpacking the Brazos River.