Innovative Technology Reveals Past, Present and Future of Water Resources (Part 2)
USGS Scientists Jim Cannia and Jared Abraham discuss the use of geophysics, a powerful new tool, in water resources studies in Nebraska
Rachael McLeod: You’re working with fairly cutting edge technology. To what extent are you still vetting the technology and to what extent are you actually collecting data for water-resources investigations?
Jared Abraham: I’d say we’re doing a mixture of both. All of these technologies were developed for mineral exploration and what’s happened over the past two decades is the US Geological Survey and some other groups throughout the world are saying, “You know, these technologies are evolving to a point we can use them for very accurate mapping of hydrogeologic environments, environmental hazardous waste sites."
What that requires is very good calibration, very good control on instrument drifts. The advancements and microcircuitry and computer technology has really lead that. So on one side, we’re applying technology that has been applied since the 50s.
On the other side, we’re pushing the limits of the technologies, saying “We need to know more accurately how well is this drift being taking care of.” The system drifts that’s fine, we need to characterize that. The use of the HEM technique, which is a frequency-domain technique, has truly become effectively routine. It’s used throughout the mineral industry. It’s not used throughout the hydrology side of work but we hope to increase its use and its acceptance in the community.
Rachael McLeod: Part of your job Jim is communicating with the public what you do and I’m kind of curious to know what the response has been. I mean, is there any disbelief that this actually works? It seems like the kind of information you collect is very important to a lot of people in the state. What’ve their reactions been?
Jim Cannia: The answer is, quite honestly, a picture is worth a thousand words. It’s a cliché but in this case very much a truism. The type of diagrams and maps, cross sections, 3D images that Jared produces in concert with us, where we apply the geology due to resistivity is quite overwhelming in its precision, accuracy and presentation.
People can look at this and understand intuitively where their aquifers are and where they aren’t. They can understand whether something can be hooked into a stream or not. It’s been fabulous to work with and I think Jared and I have spent a lot of time going around Nebraska presenting this information and it’s been very, very nice to do that.
Rachael McLeod: Did you have anything you wanted to add?
Jared Abraham: What I'd like to add is the thing that is ubiquitous across the state is presenting this information to the public, to the boards, the people who are sponsoring this, the people that have the groundwater issues. You go in very tactical side and there is some disbelief but it’s truly about the pictures and at the end of it you show them this. This is where this channel goes and you’ll get input, “Oh yeah, my well’s there. That makes sense." Or, “Well, you know, I drilled the well and I saw a hundred feet of gravel and then there was silt at the bottom.” You pull out the geophysical images and say, “Well, yeah, that’s exactly what we’ve seen.”
And those are the things that earn people confidence. I’ve had farmers and ranchers come up to me and say, “Thank you for doing this.” As an applied scientist, that’s why I’m out here doing this.
Rachael McLeod: Can you explain a little bit about what a groundwater model is and how the data you collect is plugged into those models and makes them work?
Jim Cannia: Everything in a groundwater model works in three dimensions and it is draped over this hydrogeologic framework, that’s what we describe this work as and that accuracy of the model is strictly related to that hydrogeologic framework.
If you have that incorrect in three dimensions, it’s not going to give you an answer in any dimension that is correct. The better we get those fundamentals down, the better we input data into a groundwater model, the more confidence we have in it. The questions that we ask of it and the answers we receive back.
Rachael McLeod: What are some of the challenges in collecting some of the geophysical data - I’ve heard weather is one, sometimes are flying visibility wind. What kinds of issues do you face when trying to conduct a survey like this?
Jared Abraham: For the airborne surveys, the biggest thing we have to look at is safety. Safety is number one. We have aircraft with crews flying and nothing is worth risking the loss of life or the equipment. There’s also some very strict rules on how you can fly these sorts of surveys around urban areas. We don’t fly over houses, cities, schools, areas of dense agriculture like stock yards, pig farms, etcetera.
Everything is videotaped as we go so we know where we’ve been. Community involvement. We really try to hit the media and the papers and involve the local NRDs in what we’re doing. Those are definitely the logistic challenges. The tactical challenges really derive around making sure we’re applying the right tool and what we’re doing here in this team is, it’s not a geophysics project, it’s a hydrogeologic framework project. Meaning, the geologists are working with the geophysicists, who are working with the hydrologists, who are working with the geologist to solve a complex problem.
That is truly the challenge. Bring everyone to the table and solve the problem and these can be very intense discussions. In the sense I want to see this, I want to see this channel that’s these characteristics. We cannot do this. This is not a feasible thing to do. Can you see the edges of it and well maybe, what are the edges look like. Oh, well they’re characterized by this geologic condition. This is the interaction that is allowed this to be successful. Imaging the things that matter.
Rachael McLeod: And what about some of the advantages, cost, time, invasive nature of some of the other technologies?
Jared Abraham: Well, the way the geophysics is collected, especially the airborne, you’re not drilling a hole in the ground etcetera. So, we can collect a township of data which is in the post of about a hundred thousand virtual boreholes, looks into the earth, in less than a day.
Rachael McLeod: And Jim, you’ve got a great figure on how much it costs, I think it’s per acre.
Jim Cannia: Based on our previous work here in Nebraska, it is been averaging between seven and ten dollars an acre. The costs are not constant. Simply because of mobility, destination, type of survey, all of those things that going to a contract with the private contractor to fly these.
This equipment is not owned by the USGS. The science teams actually contract out to get these things flown and then we interpret the data. So between seven and ten dollars an acre which compared to drilling a borehole every nine feet which was an example that Jared was giving just a minute ago, it is incomparable in economics and cost benefit ratio.
Rachael McLeod: Is there anything either the two of you would like to add before we conclude?
Jim Cannia: I’d like to add that the state of Nebraska has been in the forefront of a lot of this work. There’s a good reason to be. Water resources, water resource management is in the front of everybody’s mind especially the panhandle which has been in a nine-year drought.
Where we go with this in the future? We feel pretty confident that we’re getting feedback from the folks out there that they want to see this continued. I hope that it does. It seems to be the way that we’re going to ride in to the future.
Jared Abraham: What I’d like to add is, we’re sitting here myself and Jim talking with you. There are literally a cast of hundreds behind the scenes. Universities, University of Nebraska - Lincoln is a huge player. Colorado School of Mines, Stanford, all the NRDs and then many people on our team.
A team of very good geophysicists that are trying to answer this both numerically, making these figures, these 3D diagrams, companies that are adjusting and tweaking their technologies to give us the right answers. Hydrologists, hydrotechs out there collecting the information we need, logging the core. It’s hard to even put in, get your arms around, the size of the effort and how many people are involved.
Rachael McLeod: Well, Jim and Jared I’d like to thank you very much for taking the time to talk to me.
Jim Cannia: Thank you.
Jared Abraham: Thank you.