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: So, here's the thing. If the Brazos River Authority doesn't actually drop a play-by-play schedule for when they're going to crank the gates open or shut them at the reservoirs, how are we, the people actually living on the lake or enjoying the river downstream, supposed to have a clue what's coming? Since there isn't exactly a shared Google Calendar for reservoir releases, it can definitely feel a bit like a mystery from the outside. Obviously, these decisions aren't made on a whim, but do you have to be a hydrologist to understand the basics, or is there an easily accessible real time data you can bookmark to help you make actual smart decisions? We've invited some BRA experts in the studio today for some real clarity on what's actually happening when large amounts of water are released downstream and how you can prepare for that impact.
I'm Charlie Shugart, and this is Unpacking the Brazos River. Returning to the podcast are Aaron Abel, BRA's water services manager, and Judi Pierce, the BRA's public information officer. Welcome back, guys.
Aaron Abel: How's it going?
Judi Pierce: Great to be here.
Charlie L Shugart: So glad you came back in. I appreciate it. And joining us for the first time is Peyton Lisenby, BRA's water resources planner. Thanks for coming in, Peyton.
Peyton Lisenby: Yep. I appreciate it. Thanks for having me.
Charlie L Shugart: So, since this is our listeners' first time meeting you, tell everybody a little bit about your history with the organization.
Peyton Lisenby: Sure. I've been with BRA for about five years now, working as initially a water resource planner, now the senior water resource planner. You know, I'm responsible for a lot of our water right management, but I'm also part of the team that helps the day-to-day operations when we have to manage high inflow events at our reservoirs and plan for releases from our three projects.
Charlie L Shugart: Perfect. Perfect person to come in and talk about this with us today, then. Alright. So just a brief recap of what we've discussed on the pod before. The three BRA reservoirs are strictly for water supply. They don't have flood control storage, which basically means we can't hold extra water if the lake is already at capacity. There's literally nowhere for it to go, which obviously leads to the big question. When there's way more water than there is room, what's the actual plan? So, what are the factors that you guys, as BRA hydrologists, are looking at when you decide what happens next? Like, what's the actual thought process there?
Aaron Abel: Yeah. That's a good question. Seems, it seems so simple. Right?
Charlie L Shugart: I mean, yeah.
Aaron Abel: I think in the last podcast, we mentioned what comes in must go out in real time. Unlike the US Army Corps of Engineer reservoirs, those reservoirs have an enormous amount of storage. In BRA reservoirs, once they're full, we have to make releases. And those releases may come in the middle of the night or early in the morning, and we have to get up and react when those releases have to be made. The overall goal in making releases is we have to protect the structural integrity of the dams. We have to monitor lake levels all the time. We also coordinate and pay for a number of US Geological Survey stream flow gages and lake level gages throughout the basin. So, we monitor stream flow. So, in addition to rainfall directly on the reservoir that causes lake levels to rise, there's also runoff that occurs, you know, upstream of the reservoirs due to rainfall, and we monitor stream flow at those points upstream and make decisions off of that too. So what we do is we take the lake level data. Say, for instance, at Possum Kingdom, we have three USGS gages that are located at Possum Kingdom, one at the dam, one at Sandy Beach, and then one at McGinnis Point. So, there's the lake level gage, upper end of the lake, middle part of the lake, and then at the dam. And they can read a little bit differently.
Charlie L Shugart: Why is that?
Aaron Abel: Well, a good question. A lot of the time, the winds are from the north, say. Most of our dams are oriented east to west.
Charlie L Shugart: Oh, okay. Interesting.
Aaron Abel: So, the area of the reservoir that aligns with the wind direction causes waves. You know, there could be changes in the wind that cause changes to the lake level. There could be causes to atmospheric pressure that causes lake level changes. But more significantly, especially when it's raining, we have active inflows. It's more about the trend in the lake level in terms of how we make decisions. We calculate that amount of water storage over a certain period of time, and we estimate what we call average calculated inflows.
Charlie L Shugart: Okay.
Aaron Abel: And so those average calculated inflows are then compared to what we're actively releasing. If the lake level continues to rise and we're approaching critical elevation, you know, in terms of the top of the gates, we'll be increasing the release to manage the lake level below that critical elevation. And, you know, for instance, at Possum Kingdom, the top of the gates is elevation 1,000 feet above mean sea level, and that's relative to a certain datum that additionally, there's an uncontrolled spillway that is activated at elevation 1,000 at PK.
Charlie L Shugart: Could you just briefly explain what the uncontrolled spillway is? I don't think we've talked about that before.
Aaron Abel: Many dams were constructed to have multiple ways to release water. Possum Kingdom, at Lake Granbury and Lake Limestone, we have controlled spillways where we have specified gates that can be opened or closed to release water. So that's a controlled spillway.
Peyton Lisenby: Yeah. As Aaron mentioned, we have uncontrolled spillways at PK and at Limestone. And these are structures that are there as a kind of a last resort release capacity, should the controlled spillway, for whatever reason, be inadequate. These uncontrolled spillways are something we don't plan to use. They're not part of our standard operating procedure. It's good that they're there, and at the reservoirs they are. But under normal operating procedures, when everything is operating correctly, we should never need to use them, which is why we've never used them. The infrastructure at the reservoirs, you know, why are there five gates at Limestone and 16 gates at Granbury? You know, why are the gates sized the way they are? That's a planning decision that's made on evaluating what the probable maximum flood event for that location could be.
Judi Pierce: And that's done when they're designing it.
Peyton Lisenby: Yeah. That's in the design phase.
Aaron Abel: That's right.
Peyton Lisenby: The planning phase. So, you look at how big the drainage area is, what kind of storm events happen on these. It's a worst case of a worst case, you know, if all the dominoes are stacked up in all the wrong places. What's the biggest event that could happen here? And you need to make your infrastructure be able to safely pass that with some margin. Now that being said, the past is not a perfect predictor of the future. In the cases where an event may exceed the probable maximum flood, or for whatever reason, you have a situation where you don't have the full capacity of your facility because stuff happens during these big flood events, you need a fail-safe on the side to be able to safely pass any excess water without causing additional problems. And that's what I mean by these emergency spillways are exactly that. It's an emergency. This, despite all the planning that's gone into this, unforeseeable circumstances can create a condition where extra water needs to be passed that can't go through the spillway either because there's not room or, you know, for whatever reason. So, at Limestone and at PK, that availability is there now. As an aside, is anybody going to ask why isn’t there one at Granbury?
Charlie L Shugart: Can we? Because I would love to ask that.
Judi Pierce: I was just about to ask that. Yeah
Aaron Abel: You know, the analysis and the planning of that reservoir didn't require an emergency spillway because we have the capacity to release a whole lot of water. We have 16 gates, and we can release hundreds of thousands, you know, I think on the upwards of 500,000 plus cubic feet per second.
Judi Pierce: Wow.
Charlie L Shugart: So, when we're talking about making big releases, is it pretty much a copy-and-paste procedure between the three different reservoirs, or does it look different depending on which lake we're talking about?
Aaron Abel: Yeah. In terms of the BRA reservoirs, Possum Kingdom, Lake Granbury, and Lake Limestone are very, very different. Possum Kingdom has nine bear trap gates. Other folks call them roof weir-type gates. So, there's, I can't recall how wide those gates are. Yeah. 70 to 90 feet wide, I believe, and, you know, 13 feet tall. And so, it takes a lot of planning and time to open bear trap gates. Sometimes it could take two to two and a half hours to open a gate at Possum Kingdom. One bear trap gate at Possum Kingdom releases about nine to 10,000 cfs. At both Lake Granbury and Lake Limestone, those are very easily opened.
Charlie L Shugart: They don't take two hours?
Aaron Abel: They can take as little time as, you know, two to five minutes maybe.
Charlie L Shugart: Yeah. A big difference. So, is each gate at the Granbury and Limestone ones also releasing 9,000 cfs like PK?
Aaron Abel: No. At Possum Kingdom, they're either fully open or fully closed. At both Granbury and Lake Limestone, we open those at about a half-foot increment, so every six inches. So, at Lake Granbury, you know, one Tainter gate open six inches is about 440 cubic feet per second.
Charlie L Shugart: So yeah. It's a big difference then.
Aaron Abel: One cubic foot is, you know, a small beach ball. So, one gate opens at half a foot at Lake Limestone is around 460 cfs, and that's because their gates are a little bit larger than Lake Granbury's. And as we mentioned, there are only five Tainter gates at Lake Limestone.
Charlie L Shugart: Could you explain for everyone, I mean, I think when people hear that it takes almost two hours to open a gate at Possum Kingdom Lake and five minutes at Limestone or Granbury, why is that?
Peyton Lisenby: Infrastructure wise, they're very different facilities. Limestone and Granbury, as Aaron mentioned, both have electronic control of a Tainter Gate structure, whereas PK was built much earlier, and it's a completely different design. PK can be operated hydrostatically without electricity, if need be, but the way Possum Kingdom's dam, the Morris Sheppard Dam, is designed, it takes time to prep the gate chamber to be ready to lower the gates. The gates are made of two leaves, and these leaves are resting on one another, kind of making a triangle, almost with a chamber underneath. In order to drop the gates without them just falling, you have to fill that chamber up with water so that the gates float on top of that water, and then you'd let the water out slowly, and that eases the gates down the 13 foot, I believe, is how high they are, that the leaves collapse upon one another and slowly lower, that's what lets the water out. So, it takes time to get all that in action. Whereas at Granbury or Limestone, you push a button, and the little pulleys lift the ropes, and the Tainter gates are lifted up, and like Aaron said, we do that in half-foot increments. And another thing worth noting is the I guess the increment with which you can operate a gate also affects how finely tuned you can keep lake levels during an event. Right? So, with Possum Kingdom, it's an all-or-nothing type of deal with each gate. Each gate's, you know, on the order of 9,000 cfs. So, depending on the amount of inflows that come in, usually inflows are not exactly what your release capability is for each increment. Right? So, it's going to involve the lake level rising, making a release, the lake level dropping, and the fine-tuning nature of the lake level rise and drop is associated with the increment of the release from the gate. So, at Lake Granbury with 16 gates that we can all open half a foot each, you can actually finely tune the release a bit more to match what the inflows are. Whereas PK, it's a cruder or more rudimentary release capability. So, inflows that come into the lake may cause more changes in lake level as we're operating the reservoir because we're releasing such large quantities of water in each gate operation.
Charlie L Shugart: Okay.
Peyton Lisenby: So, you will see in gate operations at PK versus Granbury and Limestone the difference in how the lake level reacts because of that difference in infrastructure.
Charlie L Shugart: So, after making a big release at PK and you're done making the release, is the lake level typically just low after that?
Peyton Lisenby: In a simple scenario where it's not raining directly on the reservoir, let's say there's just inflows coming in from the river, once those inflows pass the stream gage, we know how much water. We can convert the rate of water from cubic feet per second. We can convert that into a volume, and we know what's going to fill in the lake. We also then know how much we need to release to keep the lake within our safe operating range. And as long as we know how much water is left to come in, we can time the closure of the gate so that it fills the lake back into the operating range afterward.
Charlie L Shugart: That's some specific math.
Peyton Lisenby: Yes. That's all part of the process mentioned earlier about the time step of when we will know what we're going to do with the release, and then when that information is going to go out to the public. And so that's kind of the tail end of the process. The time step with which we know what we're going to do starts with setting our expectations for what the inflows will be. And so, if you back that up, we only know the inflows when we can calculate them at the reservoir, when they've arrived at the reservoir. We have a good indication of inflows when they pass an upstream stream gage.
Charlie L Shugart: Right.
Peyton Lisenby: But beyond that, we're all waiting to see what amount of rainfall actually turns into streamflow. So, you start with the weather forecast. If we expect rain, we're paying attention, but at that point, we couldn't tell you what we're going to have to do for a gate operation. You look at the current lake level. Is it full already? Is it three feet low? You know? That'll affect the timing of the releases. Let's say the rain event does actually happen. It probably won't be exactly as it was predicted. In fact, it definitely won't be exactly as predicted. And even with that uncertainty, you still don't know how much of that rain's going to turn into actual screen flow. Right? If you've been doing it long enough and you know about how dry it's been, if it's been dry in the past, a lot of that rain might not turn into streamflow. If it's been wet for a while, most of it might turn into streamflow. So, we're waiting on that too.
Charlie L Shugart: Yeah.
Peyton Lisenby: We can't make a call until we realize how much water is in the river barreling toward the reservoir, and that's under simple circumstances. Even if you have that realization of what's in the river, what's coming toward the reservoir, if it's also raining on the reservoir, you've got immediate inflows that you have to deal with, regardless of what's coming from upstream. And so, our expectations as operators to what we are actually going to have to do release wise for the reservoirs might not be set until we need to actually make release decisions, depending on the timing and the location and the magnitude of the rainfall event. Like I mentioned before, the simplest scenarios are when it simply is delivered from upstream. We can see it coming miles away. We can make our plans. But if that's happening and it's pouring down on the reservoir, you have this kind of dual application of inflows, which causes us to have to react a bit more quickly.
Charlie L Shugart: When we're talking about large amounts of water, what is that like, what does that look like? What are those numbers?
Aaron Abel: At Possum Kingdom, we consider any release below a one gate to be normal routine.
Charlie L Shugart: So, anything under 9,000 cfs?
Aaron Abel: Yeah. Nine to 10,000. Yeah. One gate opens at Possum Kingdom with a full lake level is typically nine to 10,000 cfs. At Granbury, what we consider a high flow event, or you know, a flood event, is anything over 5,000 cubic feet per second.
Charlie L Shugart: Okay.
Aaron Abel: So, at Lake Limestone, it's 2,000 cubic feet per second. You know, there are downstream call notifications that actually go out when we reach those high-flow event criteria.
Charlie L Shugart: Okay. Tell me about those.
Judi Pierce: We have an automated system now that all three lakes can utilize. And the way it's programmed is if you choose to sign up, if you're a downstream landowner or if you're someone who does quite a bit of recreation on the river, you can sign up to be in this program that will automatically call you when we're making certain releases. And depending on the lake, you can specify where you'd like to be called. So that can occur during the day. It could occur in the middle of the night if that's when we're having to open gates. But we can notify you either by phone calls like they used to do years ago, or we can send you a text message, we can send you an email depending on how quickly you want to be notified for that. So, it's a good thing if it happens during the day. It might not be such a good thing for everyone if it happens at night because it, you know, hopefully it will wake you up. In the case of people living very close to the river or people that are enjoying recreation, might be camping in the riverbed, you need to know that as soon as possible so that you can make sure that you are not in harm's way of that water coming to reach you. You know, maybe it's not as important if you, you know, have a home that's further away from the water. So, you can sign up for any of those downstream call lists to be notified by filling out a form on our website, and that's www.brazos.org/downstream. And you would just indicate on there which lakes you would like to be notified of. One of the things I want to point out here though is that sometimes we have people sign up for all three of our reservoirs, which, you know, it's good to know if we're making releases, especially if you're way down south. You might want to know if you're in the Richmond Rosenberg area, and you might want to know what might be coming in your direction. I don't know if you'd want to know that in the middle of the night, when we first open gates, because it takes several days for that water to reach you. But, you know, Limestone is on a different river. It's on the Navasota, and it's definitely further away from Possum Kingdom and Granbury. So, you might want to be on the list for PK and Granbury if you're on the Brazos, anywhere, you know, up to Granbury or below. But you probably wouldn’t want to be on the same list at Limestone because they're a great deal of miles away from each other. So just kind of keep that in mind if you're interested in signing up. But it's available to anyone who would like to be on the list. We're not going to give a criteria. If you make the request, we'd be happy to include you on that, and you will be notified. A lot of times, people will realize, okay, I don't want to be notified at three in the morning. And so, they can change their notification to just be a text message or just an email, so that you see it when you get up in the morning. So that's also possible.
Charlie L Shugart: Yeah. Absolutely. So, you mentioned that it may take a while for the water to reach those living down south. I mean, do we have any stats on how long it takes a release to travel? Like, if Possum Kingdom opens a gate, how long before it's knocking on Granbury's doors?
Aaron Abel: Yeah. It takes around forty hours to travel from Morris Shepherd Dam to De Cordova Bend Dam at Lake Granbury. I will say it could be a little faster or could be a little bit slower, depending on what's happening in the watershed between PK and Granbury. So, you know, a lot of times we'll have rainfall events that come through and drop a lot of rain between PK and Granbury. So, Granbury's already opening gates, and we're releasing water. And then Possum Kingdom receives rainfall, and it's a much larger reservoir than Granbury. Possum Kingdom is around three and a half to four times the size of Granbury. So, for each thousand-acre feet of inflow that reaches Possum Kingdom, it has a really small amount of lake level rise. Whereas, you know, the same volume of water that flows into Granbury causes Granbury to rise more rapidly. And so, I think a lot of people don't realize that, you know, larger reservoirs take longer for lake levels to respond. You know, and that's why if you look at the stats, you know, we make releases at Granbury frequently. Part of that is, you know, we have the city of Granbury right there, and there's impervious cover, but there's also the watershed between PK and Granbury. It receives more rain than the watershed above Possum Kingdom. Limestone, on the other hand, it's a little bit larger than Lake Granbury, but it's in a much more rural area. Lake Limestone is configured a little bit differently because the top of the gates at Lake Limestone are two feet above our top of conservation, so there's additional room at Lake Limestone to respond to floods. Whereas at Lake Granbury, our operational full level is, you know, between 692.5 to 692.7. The top of the gates are, you know, around 693, and so you're talking about inches of vacant storage that we have to use to be responsive to changes in lake levels. So very, very different between Possum Kingdom, Lake Granbury, and Lake Limestone in terms of responding to rainfall and runoff and inflows.
Charlie L Shugart: Okay. So, essentially, these downstream notifications I can sign up for are going to come in really handy if, let's say, I live at Lake Granbury because I know if I'm at Lake Granbury and PK makes a release, then I have roughly forty hours before that water hits my area. Why I might want to….
Peyton Lisenby: A one-gate release. So, a two-gate release goes much faster.
Charlie L Shugart; Oh, yeah.
Peyton Lisenby: And so that only takes about, what, twenty-four hours or so?
Aaron Abel: Yeah. I think so.
Peyton Lisenby: To get to Granbury, partially because if you're at a two-gate release, you started with a one-gate release, and that has kind of prepped the channel, filled in all these little areas that absorb that water as it goes down, and slow it down. So now you have a prewetted channel that the second gate can just fire through. That's why it goes a lot faster.
Charlie L Shugart: Yeah. No. That makes sense.
Aaron Abel: There's a gage, a USGS gage at Dennis, that is seven to eight hours travel time upstream of Granbury when you're talking about a little bit more significant releases, not low flow, but significant releases. And it takes around thirty-two to thirty-six hours or so to get to Dennis. A lot of those folks that live on the river, they look at the Dennis gage, and they look at gages upstream to see what is coming down. But, you know, as far as travel times from Granbury to Whitney, depending on the magnitude of releases, it can take two and a half to three and a half days. And that's typically in normal releases. In larger-magnitude releases, the travel time between Lake Granbury and the Glen Rose area can range from 10 to 20 hours. So, I know, you know, obviously, the Glen Rose area is not quite halfway between Granbury and Whitney. You know, there's a lot of recreation in the Glen Rose area. With 5,000 cfs and higher magnitude releases at Granbury, it can take, you know, between one and two days to get to Whitney, you know, in those larger magnitude releases. So, you know, Whitney is a multi-use reservoir. It has an enormous amount of flood control storage. So, and a lot of folks that live around Whitney know that in big flood events and when we're making releases from Possum Kingdom and Granbury, Whitney can come up substantially. That flood control storage is almost 1,500,000-acre feet, 1,470,000-acre feet of storage. That amount of storage can essentially hold the entire volume of two Possum Kingdom reservoirs and almost the entire volume of three Lake Granbury’s.
Charlie L Shugart: Wow. That's impressive. So, I want to go back to something, Peyton. You mentioned earlier, if we know we're at capacity at one of the reservoirs, let's say Lake Granbury, and the weather app is screaming that we've got, you know, flash floods coming in two days. Do we start making, like, slow releases out of the reservoir to, like, catch the impact of that flash flood that's expected, so we don't later dump a bunch of water downstream where it may be raining already?
Peyton Lisenby: The short answer is no, and the longer answer is absolutely not. And I say that because a forecast for rainfall that's 10 or 15 miles off changes the implications for what that rainfall does dramatically. For example, if you have rainfall that falls below a reservoir, it's going to create streamflow that's not captured by anything. Right? And so that streamflow accumulates and off it goes. If you have rainfall that falls upstream of a reservoir, the reservoir kind of attenuates that a little bit as it passes through the reservoir and the release structure, and so it changes the nature of the flood wave as it moves downstream. From an operational standpoint, we have a forecast for heavy rainfall, and there are not just rainfall forecasts, but there are also flood forecasts as well. The river forecast centers do a good job in trying to use modeling to convert rainfall into stream flow, but that's very difficult. That's even more difficult than predicting the rainfall in the first place. So, we take that as kind of a general indication of be aware, pay attention. However, it is very far away from the certainty that is needed to actually plan releases based on that. And the big risk, obviously, the thing you don't want to do the most is make flooding worse downstream, which means if a forecast calls for rain, that rain could fall downstream. If you've pre-released, you've stacked additional water on the water that already fell downstream, you've essentially grown that flood wave more than it should have been. You've artificially exaggerated that flood wave.
Charlie L Shugart: Okay.
Peyton Lisenby: Essentially, the quality of forecasts we have now in Texas are not up to the standard, anywhere close to the standard, that will be needed to make those kinds of planning decisions. Everyone knows that in Texas, we have weather that changes quickly, but it also makes it very difficult to predict. It's not like that everywhere else in the country, but certainly in Central Texas. There's been a lot of research going on into how we can get better at predicting it. And yes, we can always get better at predicting it. We're a long way from getting that level of certainty.
Charlie L Shugart: Yeah. Okay. Interesting.
Aaron Abel: And if it doesn't rain, we've just lost valuable storage that would have been in the reservoir during dry periods. So, you know, these reservoirs were built to store water during wet times for use during dry times. And, you know, the three BRA reservoirs, you know, that's what they were built to do.
Peyton Lisenby: But there is an exception to the prerelease thing, and that is only at Lake Granbury, and it is only when we know exactly how much water is coming into Lake Granbury. In our operation procedures, we can draw Lake Granbury down to make room for a release that we release from PK.
Aaron Abel: We may be releasing, say, 5,000 cfs because there's been runoff, you know, immediately around the reservoir. But then we have run off upstream at PK, and we open a gate at PK. So, at that point, Lake Granbury's releasing 5,000, and then PK is releasing 9,000. So, we know that an extra 9,000 cfs is coming towards Granbury. So, we will, at that point, increase the release at Granbury, and we will draw the lake level down at Granbury and operate it below full. And then that really depends on the magnitude of an event. You know, if we have two or three gates open at Possum Kingdom, we may draw Lake Granbury down, you know, to around six ninety-one and operate it over two feet below full. The purpose of that, it's safer to have the lake level a little bit lower at Granbury. It creates additional time for us to respond because Lake Granbury, as I mentioned, it's a much smaller reservoir, and the lake levels can respond rapidly. So, in the event that we have a very significant event, I think, you know, we could operate it a little bit even, you know, below two feet full, maybe up to five feet full.
Charlie L Shugart: Once we've passed all that water through Lake Granbury, for instance, would the lake still be two feet low?
Aaron Abel: No. At the end of these flood events, the reservoirs will be full.
Charlie L Shugart: So, the big difference there is we're letting water out of Granbury earlier because the water is actually, we know for sure, already on the ground upstream versus, as you mentioned, the weather forecasts aren't always 100% reliable. And if we release beforehand, the rain might not fall, and we've released unnecessarily.
Peyton Lisenby: And the custom caveat applies here. If it's pouring down rain at Granbury, you know, if the weather's doing stuff, we'll be responding to that at Granbury as well. Again, you know, in the most ideal conditions, it's only PK that has a release. Everything's sunny at Granbury. We can make the accommodation, you know, at Granbury for that water coming down. But it never works out like that. Right? Granbury is doing its own thing. PK is doing a thing. These are operating principles we use to help us manage the lake levels as safely as possible given the prevailing circumstances of whatever flood event we happen to be in.
Charlie L Shugart: I mean, we talked a little bit about the recreation, particularly kind of like in the Glen Rose area. There's a lot of recreation below Possum Kingdom Lake. You know, if I'm camping in the river, are these downstream notifications all I need to prepare to make sure that I'm safe when I'm out on the waterway?
Judi Pierce: It's definitely important to prepare before you go out on the river at any time. You know, especially if there's rain in the forecast at all, or if the reservoir above where you're looking at going is already full. For instance, if Possum Kingdom is down like it is now, two and a half, three feet, you're probably pretty safe on the river. You know, we're not going to make a large release. It would have to be pretty large to fill up PK and then and need to make a release that way. But you should check that if you're going to be out because if the reservoirs are full, there's a chance that if you're camping in the middle of the night, you could be open to having a release come downstream. So those downstream call lists are really important if you're going to recreate. But they're also important for people who live near the river. But before you go out, it's definitely important to take a look at the reservoir levels, the river levels, the forecasts that are going to be going on. One of the biggest problems that we see with recreation on the river, and we get this pretty often, is that, hey, I have really reliable mobile service normally, but on the river, especially between Possum Kingdom and Lake Granbury, there are a good number of high walls and canyon areas that you cannot get a signal on.
Aaron Abel: If you have a satellite phone and you're going to be, you know, recreating below and camping overnight and there's chances of possible releases. Any way you can get information is good. And also, you know, I think making sure that somebody knows you're out there.
Judi Pierce: Absolutely. Having a plan ahead of time and letting people know where you plan to put in and take out is very important. Or if you have an idea of where you're going to be camping because there are established areas of the river that are sandbars and banks where you can camp, and they're pretty much always there unless we have a large release going on. And also, quite honestly, the places that rent canoes and kayaks South of Possum Kingdom and South of Granbury are pretty good about saying, “Hey, there's, you know, some pretty iffy weather coming up. You need to be aware of that.” And they will caution people before they go out, which is really great.
Charlie L Shugart: Yeah.
Judi Pierce: They know the river probably better than anyone does. But one of the things we hadn't talked about yet is, yes, we have the downstream call list. But when we're going to be making a release, we are up in the middle of the night. The hydrologists and the lake staff, but also the PIO staff, are up in the middle of the night to make sure that people are aware that we're making releases. So, the first thing that we do when we're notified that there's going to be a gate release is to put that change in stream flow on our website. So, for recreationists, that's one of the first places you can look to see whether or not there's a release going on at any of our reservoirs. So, about halfway down our homepage, www.brazos.org, you will see current reservoir levels. And one of the columns there shows the current releases. And so, we will change that release column at the time that the gate change is being made.
Charlie L Shugart: So that's real-time data?
Judi Pierce: That's real-time data. You can see it at any point, which is a little bit better than looking at USGS gages because of course it takes a while for that water to reach a gage, but the gage also is a little bit delayed in reporting where this is real time within just a couple of minutes. So, after we change that website listing for what the release is and what the stream flow will be, we also go on Facebook and Twitter or X now and place out there what the release is going to be. And if we know ahead of time, you know, we'll have a lot of people ask, you know, how long will this occur? And we'll try to put that information out there. But one of the most important things that we put, and we hope that people really take notice of this extremely important, is that recreation is strongly discouraged at any time we're doing a gate release. And there are a lot of reasons for that. First of all, you know, we don't want anybody to come to harm and just not be aware of it. But when a gate release is made, even a smaller one, you know, one gate release at Granbury or at Limestone is going to be a lot different than a one-gate release at Possum Kingdom. But if it's been dry in between, a couple of things happen. First of all, a lot of people who live on the river will have items stored near the river. They might have patio furniture. They might have their own canoes and kayaks stored right there. And if they're close to the river and there's a release, there's a very good chance that those items will be swept away. So, this gives people a little bit of time to remove items. But also, there are tree limbs and branches, and trash, and all other kinds of things that could be swept downstream in a release. We don't want you to be out there in a canoe or on a kayak when there are these things that could potentially really be harmful to you or your boat or anything else that might be on the river's edge. And if we're making releases and that, you know, the things that are moving downstream, like any type of foliage, any type of tree limbs, or even tree trunks, sometimes we get full trees that have fallen and are being swept downstream. They can already be waterlogged, so that means you may not be able to see them on the surface. They may be, you know, just inches below. So, where you think you might have a clear path ahead of you, there could be a very large tree trunk, you know, right in your path. So, you need to be aware that it's very dangerous, not just on the river but on the reservoirs as well. We have had major, major releases. I remember one at least a decade ago that was very large, that it swept things downstream that you would never think would be in the river. Metal storage buildings, 10-foot propane tanks, people's boat docks. So sometimes you might think, wow, this is great skiing conditions. I can get out on the water. It's deep, and I can take my family out, and it'll be a good time until you see something that's floating in the in the river or you may not see it and you may end up running into it with your boat, which could cause a great deal of damage to your boat. But it could also cause someone on the boat with you to be thrown from the boat. So definitely, when you see a gate release being made, recreation is strongly, strongly discouraged. One of the things that we want to bring to people's attention is that deaths have occurred in the past because of this. It's not as rare as you might think, and we want to make sure that that doesn't happen to anyone in the future.
Charlie L Shugart: Yeah. Absolutely.
Judi Pierce: So, when large releases are being made at any of the reservoirs, at Possum Kingdom Lake and at Lake Granbury, we have what's called centerline buoys. We put them out there in order to show the deepest part of that reservoir. And they're anchored down. They're anchored down very well. But during gate releases, because we have water coming in and then water being pulled out through another gate, it tends to make those centerline buoys move, no matter how well they're battened down there. So if people get out in a boat, they're thinking, okay, I can follow these centerline buoys, and I should be okay. I won't go into a stump field, or I won't have to worry about hitting anything. And that's not necessarily the case because during large releases, they can move. So please don't go out and think that you can be safe by following the centerline buoys. Now, after a gate release is finished, our maintenance crew and our lake rangers will get out there, and they will put them back where they belong, within, you know, just a number of days after the release has settled down. But don't count on them as a safety measure during a gate release. Just one more reason to not go out on the water while we're having gate releases.
Charlie L Shugart: Yeah. Especially since you mentioned that large debris could be floating through. That debris doesn't care where those buoys are.
Judi Pierce: No. And it could snag the buoys and take them entirely out. We've had them disappear before.
Aaron Abel: One thing, Judi, and I'm glad you brought this up, you know, about the website and the information that is on our website. I want to let folks know that and I know, you know, whenever it rains, especially at PK and upstream, there's a lot of questions of, like, you know, when are we going to open the gate? When are we going to open the gate? When are we going to open the gate? As soon as we know that we're going to need to open a gate, we try to put information out there that says, you know, there is a potential that a gate release at PK will be needed. And you mentioned, you know, this data, this information that's on our website is more than what you can get anywhere else because we're trying to let everybody know as soon as we can when that will happen because, you know, it is especially at PK, it's a big deal.
Judi Pierce: Especially at PK. And that actually is something we do a little bit differently, on our website, than for the other two reservoirs, because the releases from PK are so large. We try if we know ahead of time, it could be days if we know it's coming, or it could just be a number of hours. But especially for Possum Kingdom Lake we will put it at the top of our page that we are going to be opening a gate. And we try to give you an idea of when that might be. It might be today. It could be tomorrow. We're going to let people know that we're going to open that gate so that they can plan ahead. We get a lot of fishermen directly below Possum Kingdom. Good fish in there.
Aaron Abel: Stripers.
Judi Pierce: Stripers are good.
Aaron Abel: Yeah.
Judi Pierce: And it draws a very large crowd, and we want to make sure that people are not driving for several hours to get out there with a great plan to fish for the day when we're going to be opening a gate. So, you know, for any kind of recreational activities, you may not be going out with a plan to float the river, but you might be planning to go out to fish. So, you know, take the time to take a look at our website. If we know we're going to be making a release, we're going to make sure it's out there, especially for Possum Kingdom.
Aaron Abel: And alternatively, there are times and events where, you know, we may get you know, and I remember March 2020.
Judi Pierce: We do.
Aaron Abel: We had five to six inches directly on PK, and we had to open four gates within a matter of, I don't know, it was probably five to six hours. And we try to get, you know, as much information to you and your staff as soon as we know that those types of situations occur. And it's one of those things that, you know, and going back to what Peyton said, we can't be all-knowing, especially with the weather in Texas.
Judi Pierce: Well, know, that's really the great thing about social media now is that we can update people by the minute on our social media channels as Facebook and X or Twitter is what we use to let people know what's happening. So, in advance, we'll take notices from the River Forecast Center and post those on our pages so that people know, hey, there's a good chance that there may be some rainfall coming in my direction. And then if the gate changes, you know, once we announce them that they're actually occurring, we can make minute-to-minute changes on social media. So, if people are concerned, they can watch those pages to make sure that they know what's coming in their direction as the forecast or the rainfall changes and perhaps moves out. We can go on and let people know it's not as bad as we thought it might have been, and we're going to be closing gates rather than opening. So, we do that as well.
Aaron Abel: You mentioned the National Weather Service West Gulf River Forecast Center, and I want to take some time to commend those folks and explain, you know, and this may be another podcast, but the West Gulf River Forecast Center they are a group of hydrologists that are officed in the National Weather Service Fort Worth office. They oversee the forecast of the river. They take into consideration rainfall, runoff, but they also coordinate with all the reservoirs in Texas for the most part, and New Mexico and Mexico to come up with the best forecast that they can for, you know, gage points and forecast points downstream of these reservoirs. And they coordinate with, as I mentioned, with all the reservoir owners like BRA, LCRA, TRA, Sabine River Authority, just everybody. They're a group of outstanding scientists and engineers, and I can't say enough about those folks, and they are the ones that model the river and then pass that modeling data onto the forecast office that then issues the warnings, the flood warnings when a gage gets to a certain point. I think that's important to emphasize that our interagency coordination, you know, as well with the Corps of Engineers, as we mentioned, you know, in a previous podcast. Anyway, I wanted to emphasize that.
Peyton Lisenby: There's something I think is worth coming back to in relation to the discussion about how, if possible, PK specifically, when we can plan ahead of time, we'll let people know, hey, we may open gates early to give them a little bit of prep time. Part of that is, and I know we've mentioned before, that it can take some time to get a gate open at PK. But along with the planning of the potentiality of opening a gate, we can help reduce that time that it takes to open a gate at PK by floating them, as we call it. When you open a gate at PK, you first must float the gates in a filled gate chamber, and then the opening of the gate is actually releasing the water out of the gate chamber. You don't do that part, if you leave the chamber full of water, the gate's floated, you've saved yourself a ton of time should you need to open that gate later. If we do think that it's likely that we will have to open a gate, on our end, from an operational standpoint, we'll make an assessment of if we need to float one or more gates so that when the time comes, we don't actually have to take the full two hours to get the thing open. We can actually open them in a matter of less than an hour. We look at the potential magnitudes of what's forecasted and make a judgment call on how many gates we'd like to float. However, that doesn't mean those are the only gates we can drop. If we drop gates and we see that the event is going to continue, we can float gates while we're dropping gates as well. Float additional gates to maintain the timeliness of our reaction to what's happening with the rainfall event.
Aaron Abel: In events in the past where we've floated, you know, some gates, there will be folks that misinterpret that as, oh my, you know, they're actively releasing water. And, yes, we are actively releasing a little bit of water. You know? And for instance, one gate floated is roughly around 20 cubic feet per second. That's two zero cubic feet per second. Not the 9,000 or 10,000, that is a clue that we've picked up on something in the weather world that may cause us to open a gate.
Peyton Lisenby: Doesn't mean we're going to open it. Plenty of times we floated them, and then we didn’t drop them, and we put them back to their lock status. We'll drain, you know, drain the chamber and, you know, that was that. The rainfall didn't happen. That happens a lot.
Charlie L Shugart: Okay. Yeah.
Aaron Abel: Better to be prepared than not.
Judi Pierce: Well, and for the safety of our own staff that have to go out literally on top of the dam and unlock those gates manually, they literally go out there and pull pins out of the top of the gate to unlock it. So, it's better that they go out and do that ahead of time and are prepared by floating a gate rather than somebody being out there in the middle of a squall with a harness on 13 stories above the ground and unlocking those gates. So, it's for everyone's benefit that we do that ahead of time.
Peyton Lisenby: To the extent we can, when we're floating gates, you know, if we know a storm's coming, we'll try to do that before the storm gets there, you know, in daylight.
Judi Pierce: Right.
Peyton Lisenby: Obviously, we do not get to pick the time these events happen, and certainly, we have to operate at night and in inclement weather. The project staff do an excellent job managing that risk. But from our end, from a planning standpoint, to the extent we can, if we do need to unlock gates to float them, obviously, we're going to do that so that staff can do it during daytime hours. They can see what they're doing, and in good weather. And again, if the weather cooperates, we get to do that, but that doesn't always happen.
Charlie L Shugart: Yeah.
Aaron Abel: One of the things at Possum Kingdom when we really have to coordinate closely with not only internally but externally is at Possum Kingdom, once we reach two gates open, which is around 18,000 to 20,000 cubic feet per second, we start to think about that third gate being open.
Charlie L Shugart: Okay.
Aaron Abel: And that's significant because, as everybody, especially those who live around Possum Kingdom or have visited Morris Shepherd Dam, you drive across the river just downstream, the beautiful Highway 16 Bridge, that goes underwater once we open the third gate.
Charlie L Shugart: Oh, wow.
Aaron Abel: So, there's a lot of coordination that's needed between BRA and TxDOT and the other local law enforcement to prepare that. And, you know, it's a significant issue, I will say, because it does cause folks to have to go out of their way to get from one side of the lake to the other. And I think, Judi, I can't remember what the mileage is.
Judi Pierce: It's about a forty-five-minute extension of time in driving once that bridge is closed.
Aaron Abel: If it's at all possible, we try to manage releases to avoid that third gate, but sometimes we can't. And no discredit to Lake Granbury and Lake Limestone, but those are easier reservoirs to manage. And Possum Kingdom takes a lot of coordination. It takes a lot more time and energy. You know, we do that for the protection of the dam and for everybody.
Judi Pierce: For people's safety.
Aaron Abel: For people's safety.
Judi Pierce: And if I can mention something here, which is just a very good example of turnaround, don't drown. When we have that third gate open, the water will come up, just maybe, you know, six to eight inches just above the top of that low water bridge. And TxDOT comes out, and they will put barricades up on both sides of the river. Sometimes they'll even have, you know, officers standing there. And people will still go around those barricades and try to cross. It's very, very dangerous. There are no guardrails on that bridge, and it's very possible that the streamflow could wash a car, even a large SUV, off of that bridge. So please, if it's shut down, don't go around the barricades and try to cross the Low Water Bridge. It’s a 45-minute drive to go in the other direction, but it's well worth your life.
Charlie L Shugart: Yeah. Absolutely. Well, everyone has mentioned several times that people look at the USGS gages to kind of determine what the stream flow is. If that's something that I want to do, how do I go about doing that?
Judi Pierce: We have a really, really great companion site to our website. It's called BrazosBasinNow. And it's just an easier way to take a look at all the USGS gages that are located within the Brazos River Basin. So, it's all of them, not just between our three reservoirs, but all the gages that are located. They also show the gages that are available on the reservoir. So, if you're interested in looking at lake levels, you can look at that. But it also shows rainfall. And it's really pretty current information within a thirty-minute period, and how much rainfall has fallen in certain areas. So, if those are areas of interest to you, it's a great site to take a look at. It's www.brazosbasinnow.org. Good information. And you can watch stream flow at each one of those gages. The other thing Aaron mentioned earlier was the National Weather Service's Hydrologic Prediction Center. So, I think that's what it's called now. Those predictions are linked on BrazosBasinNow. So if you know an area that you're going to be in, say for instance, the Dennis gage, they actually have a prediction service that will tell you about how high they think the river will get in that area, when it will crest, and when it's expected to come down. And that's been great information for people that live in the area to know, okay, I should be okay until this point. And then at that point, the river level will start coming down. So that prediction service has been a lifesaver for many, many families that live on the river.
Charlie L Shugart: So we can just go to BrazosBasinNow and see how much it's rained over a different amount of time, the stream flow in the particular area that I'm interested in, and then the National Weather Service's hydrologic predictions graphs that show when the river's going to crest or kind of start coming down.
Judi Pierce: Yeah. Absolutely. Very good site.
Aaron Abel: And the reservoir levels. I think you probably mentioned that, but
Charlie L Shugart: I don't think I said it. And the reservoir levels. Yeah. And for everyone listening at home, don't be intimidated by BrazosBasinNow. If you get on there and you're trying to figure out where the gages are in your area, how to read that information, just even how to navigate that site, please reach out. We’re happy to help with that. It's not as scary as maybe it looks initially. And once you kind of get the hang of it, you're just going to be super grateful that that information is there and available.
Judi Pierce: Absolutely. People can call us. If they just need someone to walk them through how to use that BrazosBasinNow, give us a call. We have a toll-free number, (888) 922-6272, and we are happy to answer your questions, walk you through it, so you understand well what will help you in a flooding situation.
Charlie L Shugart: So, since we're talking about big releases, do you guys have any, stats on what some of the bigger releases we've had over the years?
Peyton Lisenby: Yes.
Charlie L Shugart: Yes.
Aaron Able: Yeah. Sure.
Charlie L Shugart: Do tell.
Peyton Lisenby: We'll start with Lake Limestone just because it was more recently made the list change a little bit. So, Lake Limestone, we recently broke the peak record peak release at Lake Limestone back in '24. Spring of '24 was a very active spring across all of our reservoirs. But at Limestone, we had a peak release of over 77,000
Charlie L Shugart: Wow.
Peyton Lisenby: Cubic feet per second. That was May 2nd, 2024. Previously, the record was 56,000 approximately cfs. So, it broke by a good margin.
Charlie L Shugart: Yeah.
Peyton Lisenby: Lake Limestone doesn't have a huge basin upstream like PK and Granbury does. But based on its location in Texas, it can get more torrential and higher magnitude rainfall events. So even though it's a smaller drainage area, the amount of rain that falls on it and the rate that that rain falls, at least in my experience, over the past five years, can be more than elsewhere. And so that event, I remember it was not only raining hard above the basin and causing all the streamflow coming into the reservoir, but it was raining many, many inches on the on the reservoir itself. So that affects not only how much we have to release, but how fast do we have to release it in order to keep our lake at a safe operating level. Granbury, it's been a bit longer since we had our record release. That was over 79,000 cfs at Lake Granbury back in 1990. The previous record or no, excuse me, the next peak release of interest, even though it's a little bit lower, I think this is what, and I've only heard of this because this happened before my time, but this was the flood that ruined Christmas.
Charlie L Shugart: Oh, no.
Peyton Lisenby: Yeah. And that was
Judi Pierce: '91.
Peyton Lisenby: Yeah. '91. So that was the peak of that was actually about 71,000 or so cfs on 12/20/1991. So anytime, you know, I see that peak in our historical files and everything, I just think of the flood, the flood that ruined Christmas.
Aaron Abel: Yeah. The flood that stole Christmas or
Peyton Lisenby: Yeah. A lot of people were up and working around the clock during the event, through the holiday.
Judi Pierce: Right. And it's interesting because some of the old timers that we've talked to down below Lake Limestone or in the lower part of the Brazos Basin will tell us that they would put out stakes as to how high the water got during that ‘91 release because it was so large that they could compare everything else to the stakes in the ground from the '91. This might be a good place to bring up something that actually, that we have absolutely nothing to do with, but in high flood, releases, a lot of times, not just the, bridge at Possum Kingdom Lake, but other bridges will have to be closed because, you know, the water gets high, that happens sometimes to the bridges that are below Lake Limestone. So, a great source to look at, you know, if you're heading out after a flood event, is a site called drivetexas.org. And they will show you which bridges are closed or which highways may be affected by flooding. So, it's a good thing to have in the arsenal for when we have heavy rain events.
Charlie L Shugart: Yeah. That's helpful.
Peyton Lisenby: It's the last reservoir, so PK on its peak releases. You know, there are nine total gates of PK. We've never had to open all nine for a flood event, which is wonderful. I'd like to continue that. But in the past, we've opened as many as six, but it has been a lot longer. So, the most recent six-gate release at PK was back in August 1978. Prior to that, it was all the way back in the fifties, the last time we had to open six gates. A gate is about 9,000 cfs. That can vary depending on lake level, but roughly 9,000. So, six gates, you're, you know, easily over 50,000 cfs in your release if you've got all those open at the same time.
Aaron Abel: You know, obviously, spring is a rainy period, you know, essentially April through June, but we also have a secondary period where it's typically in October, maybe, but, you know, obviously, we have the Gulf of Mexico. We have the Eastern Pacific, and hurricanes, decaying hurricanes, and tropical storms have probably provided the biggest flood events, especially in PK's history. And that '78 event was, you know, in August, as Peyton mentioned, and that was due to the remnants of tropical storm Amelia. Areas upstream of PK received over 29 inches in twenty-four hours.
Judi Pierce: Wow.
Aaron Abel: And that's what generated the runoff that caused that six-gate release, you know, in '78. So, floods can happen pretty much any month.
Charlie L Shugart: Alright. Well, that was a total master class. Huge thanks to Aaron, Peyton, and Judi for swinging by and dropping all that knowledge on us. I hope you guys will be willing to come back in the future for more episodes.
Aaron Abel: Absolutely. Yeah.
Judi Pierce: Whenever needed.
Charlie L Shugart: So, for everyone with this buzzing in their ear, if you have any follow-up questions or have an idea for an episode on a topic you'd like to know more about, slide into our inbox at information@brazos.org. We're always hunting for the next deep dive, so don't be a stranger. Anyway, that's the tea for today. Thanks for listening to Unpacking the Brazos River.