Here's Why The Highland Lakes Are So Important (And Why They Aren't Really Lakes At All)

Oct 20, 2018

Over the past few days we've been hearing a lot about the Highland Lakes and the system of dams in the area. As all of that water makes its way down the Colorado River, we thought this would be a good time to get an explanation of exactly how that system works.

So we asked KUT's Mose Buchele.

  This transcript has been lightly edited for clarity.

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When a lot of rain falls upriver in the Hill Country, what happens to all of that water? Does it literally just all come down the river?

Yeah, I mean, ultimately it does. We have a bunch of different rivers that then feed into the Colorado River. Each of these rivers – and I'm talking like the Pedernales, the Llano, the San Saba – they have their own river basins. It floods in those basins and those rivers collect water. That goes to the Colorado, and it can kind of, you know, gain steam as it moves along and create the kind of situation we had this week, which is a river flood essentially.

So those rivers all feed into the Colorado River, which goes through Austin?

I want to make a point right now: A lot of what we talk about is lakes in Central Texas, and I think a lot of people don't quite understand this maybe – especially people who have recently moved here. These things we call lakes are really part of the Colorado River. So Lady Bird Lake, Lake Austin. You might go to the shore of the lake and think of it as a lake, but actually when you get a big rain event like this, you realize - no, this is a river and it can go really fast.

So talk about this system of dams along the Colorado River that helped have helped create this system of lakes.

That's why we think of them as lakes, because they are dammed off, the rivers dammed off rom Austin on upwards into the Highland Lakes. And that system is created for a few purposes. It was created for agricultural storage, and people use it now, of course, also as a kind of recreation.

Lake Travis also has this capacity to hold flood water, and that's really what we're talking about right now. What we had was severe flooding on the Llano River, a lot of water rushing into the Colorado River, and we saw the damage that flooding created all week upstream of us and even along Lake Travis.

Now, Lake Travis is really full of water, and I think the statistic that we've been using is that in the last week Lake Travis got four times the amount of water from these floods that the City of Austin uses in a year - just to kind of give you a sense of how much water has just rushed into this one reservoir. And, now, the Lower Colorado River Authority, which is the agency that manages these things, is trying to figure out how to move that water down the Colorado River. There's only so much room in Lake Travis, so they can't let too much more water get in there. But they also don't want to exacerbate flooding farther downstream.

So it sounds like that's where the system of floodgates comes  – to start alleviating some of the pressure of that water, right? Talk about how a floodgate works.

There are different kinds of floodgates, but in its most simplest sense, what you have are a series of openings you can create in the dam to let some of that water through. So, then [opening the floodgates help] lower, or begin to lower hopefully, the water levels on the other side of the dam. So, you know, Lake Travis, I think, is at about 704 feet right now. [The LCRA has] four floodgates open, and what we've been reporting and what everyone has been talking about is the notion that there's a possibility they could open more floodgates, if the lake gets higher than that 704. If it hits 714 feet, it activates the spillway, which is something the LCRA does not want because that could endanger houses.

What's a spillway then?

Essentially, it's like a release valve for the extra water that they don't want. The last thing you want is a dam to overtop, right? So, this allows the water to kind of bypass the dam and then spill back down. But, like I said – and this is kind of a policy issue in Texas, too – in a lot of a lot of places, there are actually properties in the spillways. And so, you're dealing with people's lives then.

Then that becomes a decision of, 'Do we open floodgates? What happens with this spillway?'

Lots of factors go into these decisions. These are things that people are probably staying up late all night thinking about this last week.

If more floodgates are open, what can Austin expect to see?

What the LCRA was talking about earlier this week – and what they say they thought might still happen – is that they go to eight floodgates. If that happens, we'd see a lot of flooding along the parks along the river and more flooding along streets. Obviously, we're seeing rain today, and that could add to flooding. It's still really a fluid situation and a lot of it depends on the weather.