3-D Geologic Model of Columbia Plateau Aquifer System

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[Steven Sobieszczyk] You are listening to episode 15 of the USGS Oregon Science Podcast for Tuesday, February 8, 2011.

 

In this month’s episode we discuss how 3-D modeling is used to examine groundwater in the Columbia Plateau. USGS hydrologist Erick Burns describes how his team modeled the 53,000 mi² plateau, how this information is currently used, and what implications it has for the future. Join us, as we explore how cutting edge science today is used to solve tomorrow’s problems, only in this month’s episode of the Oregon Science Podcast.

 

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[Steven Sobieszczyk] Hello and welcome. I’m Steven Sobieszczyk. You are listening to and watching the USGS Oregon Science Podcast. Today I’m joined by USGS hydrologist Erick Burns. Erick is part of a team of USGS scientists who are modeling the aquifer system of the Columbia Plateau. Thank you so much for joining me today, Erick.

 

[Erick Burns] Thanks, Steve.

 

[Steven Sobieszczyk] First off, Erick, can you give us a little background on this study?

 

[Erick Burns] The piece I’m going to talk to you about today is actually part of a much larger study funded by the U.S. Geological Survey Office of Groundwater. The overarching goal of this study is to understand the water resources in this area. There’s been some concern over the past 20 or 30 years in this area, or even longer, because declines have started in a lot of the water wells. So water levels are declining. This area is reliant on groundwater for a lot of its industry. And to give you an example of that, last year I think it was, there was about $6 billion in agricultural production from the Washington area alone.

 

[Steven Sobieszczyk] With such a large area, how do you go about investigating water resources for the Columbia Plateau?

 

[Erick Burns] We use a couple of different tools. We collect a large amount of data, we do a lot of analyses of this data, but to really get a good look at it we use some tools called models. We use a couple of different types of models. One is a conceptual model. So the conceptual model is really just our general understanding of where water comes from and goes to. And how it might move through the ground. Beyond that you take conceptual model and move it into the next tool we have, which is a computer simulation model. And the computer simulation model…with that what we do is develop the shape of the system. And then we know how water flows through the geologic units, and so what we do is simulate the physics of how water will flow through these units and from that we can start to say, “well, is the system behaving the way that we observe?” 

 

[Steven Sobieszczyk] What geology is actually making up this Columbia Plateau?

 

[Erick Burns] So three of the model units of the four are Columbia River Basalt. The last unit is kind of what we call sedimentary overburden unit. If you want to see kind of what one of the lava flows looks like you can go into the Columbia River Gorge between Portland, and say, the Dalles, and you can see nice, nice examples of these lava flows, of these massive lava flows.

 

[Steven Sobieszczyk] Can you describe a little bit of each of these different layers, what they’re composed of, and how they function and the way its been mapped?

 

[Erick Burns] So this first surface is the older bedrock top and if you take a look at it the two things we did with it was…is you can see this top surface, but you can also see the rivers. We left them on on top of the whole thing. So the distance between the rivers and this surface is what’s actually filled with the geologic units. If we turn on a second layer here, it’s that first basalt unit. This one’s called the Grande Ronde Basalt Unit. And it’s actually the thickest of the lava flows. It constitutes about 90% of the lava of all the units we’re going to talk about. As we turn on another layer here…this is the Wanapum Basalt, which is the next unit up that we modeled. It’s another basalt. It’s pretty obviously a smaller amount of lava. And because it didn’t go as far we believe it might have a different control on flow. If we turn on the next layer its actually the last basalt. It’s the Saddle Mountains Basalt Unit. If you look at it, it’s again a smaller unit of lava and it doesn’t cover anywhere the same amount of area as the older ones. Okay. If we turn on that last piece, that’s the sedimentary overburden. And you’ll see that it doesn’t really cover the whole area. What it’s done is its really just filled in the valleys that were created in the top of these lavas. And so this is really the heart of what we’ve done…these three models.

 

[Steven Sobieszczyk] What do you envision the use for this groundwater, this aquifer model?

 

[Erick Burns] People will use it to try and figure out where they might get water, you know, which units. The states, the municipalities, use it to figure out where is the water coming from because they need to manage water in the state so they can assign water rights. But one of the fun things we did with this one that we haven’t done in the past is we’ve developed a map interface that you…anyone can play with. Basically, someone can go to this link…and here I’ll drive it a little bit to show you what’s going on. If you look at it right here its kind of faded out it’s the geologic map. Which is basically what geologic unit is at the land’s surface in our simulated model. And there is a little slider bar here that you can move up and down and you can make it darker or lighter to make it easier to see. But this is our simulated area. And the next thing you can do is anywhere in this area that you are interested in…like say maybe you wanted to drill a well. And you want to know what you will encounter and where you might encounter it. You can click on this and it will generate this well log on the left. So another thing you can do is click on another spot over on the map here and go over here to this button and hit create cross section. If you do that what it does is it draws a picture here. This is a geologist’s tool to see what the subsurface looks like. If you notice here on the cross section tool there is two windows. If you’re really interested in something in one, you can even zoom in on it here.

 

[Steven Sobieszczyk] Well, thank you so much, Erick, for joining us here today.

 

[Erick Burns] Thanks, Steve.

 

[Steven Sobieszczyk] Well, that’s all we have for today’s show. Thanks so much for joining us. You can check out all of the links we talked about in today’s podcast in our show transcripts. You can find them at our website: or.usgs.gov/podcasts. If our monthly podcast doesn’t feed your need for USGS-related news here in Oregon, you can follow us daily on Twitter at “USGS_OR.” As always, if you have any questions, comments, or complaints about the USGS Oregon Science Podcast, please feel free to email us at oregonpodcast@usgs.gov. Thank you for listening. To hear more about other research the USGS is doing around the country or around the world, check out any one of our other USGS social media outlets at usgs.gov/socialmedia. There you can listen to other USGS podcasts, as well as find links to USGS on Twitter, YouTube, Facebook, and Flickr.

 

Until next time. I’m Steven Sobieszczyk.

 

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This podcast is a product of the U.S. Geological Survey, Department of the Interior.

 

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