An invasive plant on the shores of Utah's Great Salt Lake is causing an unexpected problem – it's draining freshwater from a system already under drought stress and potentially turning the lake even saltier. Hear from two scientists with expertise in hydrogeology working together to find out exactly how much latent heat, or evapotranspiration, is in flux over this incredible wetland habitat.
Transcript
Jess: Utah's Great Salt Lake is the largest saltwater lake in the Western Hemisphere, caused by weathering and runoff of rainwater and snowmelt from the nearby Rocky Mountains. These wetlands offer crucial breeding grounds for pelicans, incredibly biodiverse habitat, and are an important stop for migrating birds on the Pacific Flyway. Why does Utah have a flux measurement network? What motivated you to measure these fluxes around the Great Salt Lake?
Paul: I think Danyal is best suited for addressing why we're monitoring the Great Salt Lake because he's leading the charge there. My background is in hydrogeology. My main interest was understanding water vapor moving into and out of basins and understanding them as part of a greater groundwater budget. So, we're focusing on pteridophytes and plants that use groundwater and looking at consumptive use from crops.
A major way that water leaves the arid state of Utah is evapotranspiration. The only way that water leaves the Great Salt Lake predominantly is from that evapotranspiration (ET). We as a state are very interested in understanding that component, and it seems to be one of the most poorly constrained components of the water budget. There have been some really great advances in remote sensing technology and estimates of evapotranspiration from space using assumptions about the amount of heat available at the land surface with Landsat and Sentinel data, especially Landsat because it has a thermal band. We can estimate ET. That is a great tool, but Utah had very little ground truthing or checking those estimates. And there's a lot of interest in expanding.
With my experience in doing water budgets, estimating ET based on those, the state assigned me to work on doing some of this ground truthing and setting up a network. Most of our supports come from the Colorado River Authority of Utah, which is another state agency. They represent Utah in the Upper Colorado and Lower Colorado River Basins as a multi-state arrangement. That was kind of our main task, but these are fantastic research instruments. Each one of these stations has a massive array of different instruments for measuring heat and gas flux.
In the meantime, we're also trying to leverage them for valuable agricultural and arid ecosystem research. That's what led us into working with Danyal's group at Water Resources around the Great Salt Lake, and I'll let Danyal elaborate.
Danyal: Thank you, Paul. The project started under a bigger project, which we call the Great Salt Lake Basin Integrated Plan. The Great Salt Lake (GSL) Basin Integrated Plan was related to ensuring a resilient water supply for all uses in the GSL Basin. One of the major components of that plan was to quantify the water resources in the Great Salt Lake Basin. The Great Salt Lake Basin is a terminal basin. All the rivers and the groundwater flow to the Great Salt Lake, and there is no outlet, except for the evaporation. Evaporation is the only way that water can leave. The range of evaporation that happens from the Great Salt Lake and the surrounding wetlands can be anywhere between 2 to 5 million acre-feet. It's a very huge quantity.
We started looking for other examples, how people have dealt with determining the evaporation from an environment like the Great Salt Lake. We also found some studies, such as the Dead Sea evaporation study, that was done by some others from the Geological Survey of Israel and other institutes. We thought we can test the eddy covariance instruments in this environment.
The phragmites tower is actually one of the three towers that we have worked around the Great Salt Lake. There are two other towers. One is on the mudflats which we call the Great Salt Lake playa, and another one is on the Great Salt Lake mineral ponds. It's a study where we are trying to assess the water budget. In this case, since the outgoing component is the evaporation, and it's the least understood aspect. So, we have put these three towers as a pilot study to see how the eddy covariance can perform in this challenging environment.
Paul: We've been collaborating with the University of Utah. They are the ones who operate the mineral ponds and the playa site. John Horel's group, he has a couple students and Colin Johnson working on that site and they've been doing a really great job and teaching us some stuff about working with data. My understanding is this is a pilot to branch out a little bit more, try to measure more ET around the lake.
The lake is a very heterogeneous system. It's very large and complex. Water resources has broken it into some major groupings of ecosystems, wetlands being one of that, playas, mineral ponds. Open water is one that's really important and equally complex, especially when you think about [that] the Great Salt Lake could potentially be stratified because of density and/or temperature, and it has many different depths and different salinity. All of these factors play into the amount of evapotranspiration or evaporation we're seeing on the open water. Yeah, it's really complicated, and we're trying to better understand this major way that water is leaving in a huge potential range of potential loss of water.
Jess: Is that a challenge with the imagery from space?
Paul: OpenET does a fantastic job. Most of their models have been tuned to measure agricultural evapotranspiration very effectively. So far, our measurements in the flux network have indicated that it's very accurate measurements for agricultural settings. Now, when you get into open water settings and mountainous settings, which both exist in this state, it gets much more complicated. It's hard to measure ET in a mountainous setting, let alone estimate it with satellite, just because of aspects, all the interesting turbulence occurring. And open water is especially challenging. We're still trying to hone in, and we don't have any actual measurements of completely open lake water yet so it's going to be interesting to see how that compares - other than the playa site, which is periodically inundated, and the evaporation ponds used to evaporate water and produce salt, [which] are kind of open water.
There's a lot of important industry: brine shrimp, mineral ponds, and it's a hub for migratory birds, a major flyway. So, there's a lot of different interests at play here. And then, there's been some very concerning evidence that some of the dust, if the lake bed dries out and mobilizes from wind, could be detrimental to people's health. A big part of the population of Utah is adjacent to the lake.
Jess: The decisions made by surrounding states, are those important?
Danyal: The Great Salt Lake is in the Great Basin Region. So, it's not hydrologically a part of the Colorado River, but a lot of the Colorado River is imported to Great Salt Lake Basin. Hydrologically, there is no connection, but the Colorado River water does come to the Great Salt Lake Basin through the Central Utah project and others. There are reservoirs which supply water to the M&I (municipal and industrial) uses in the basin. That water after use ultimately goes to the Great Salt Lake as well.
Note: Although the GSL Basin is not physically linked to the Colorado River Basin, water is imported from the Colorado River through the Central Utah Project. About 27% of the water used in Utah originated in the Colorado River. Additionally, research suggests that the water level in the GSL could be used to predict water supply in the Colorado River Basin due to strong links in climate and hydrometeorological variations across the two basins.
Paul: Salinity is an important factor. There's a lot of different things at play here. The major contributing river that feeds the Great Salt Lake is the Bear River. It starts in the Uintas, which is in Utah, and it goes through two different states before it comes back into Utah and enters the Great Salt Lake. It goes through Wyoming and Idaho. Then the Colorado River starts in Colorado, but there's a lot of tributaries. So, there's a lot of different interstate-type dealings and agreements that are way above my pay grade. It's really important to understand measurement and states are trying to strategically come up with ways to optimize efficiency of water application. And, that's especially true with the Great Salt Lake, right?
We are trying to manage this system which we don't want to dry up, and if it does drop to a certain level the salinity does increase, which is bad for some of the things living in it, like the brine shrimp. The DNR has created these different thresholds of salinity and lake level that are ideal for these different ecosystems around the lake, and kind of give it these values, so people can understand: What are the consequences when the lake drops to here, versus here? There's a lot to unpack there with policy and also with the science. Our work feeds directly into policy decisions. It's cool to see the science get applied so rapidly, be so useful to people.
Jess: How do you know that phragmites australis, or common reed, is an invasive species? What qualities make phragmites australis harmful?
Danyal: If we just look at the terms of the water loss, it's really harmful, as far as the evaporation. The wetlands are connected to the Great Salt Lake, right? The inflows from all the three major river basins that end up in the Great Salt Lake is routed through the wetlands. So the phragmites vegetation, if it is a lot of vegetation, then we will have a lot of ET losses and less water ending up in the lake. We want more water to go to the lake to prevent the lake going down because it has ecological consequences as well as, even, economic. It is definitely harmful.
Paul: It's different from some of the native vegetation in the sense that it prevents certain types of nesting necessary for some of these waterbirds, and other things that typically live around the shores of the Great Salt Lake. The water component is definitely what we've been focusing on.
Jess: So, are you going to compare the flux data over the phragmites to a site where there are no phragmites? Are there even sites without phragmites on the lake?
Paul: We got really lucky. Another division within the Department of Natural Resources, Forestry, Fire, and State Land, they are in charge of dealing with this invasive species and trying to mitigate it. They reached out to us, and we picked a site that we knew that they were going to treat in the near future. We're going to measure prior to their treatment, and then after, and during, of course, trying to get an understanding of how the hydrology and the gas flux and the energy flux varies from this treatment. We do also have a number of sites all around the margin of the lake that have been treated already or haven't had this level of encroachment. We can supplement our understanding with some of this remote sensing data, assuming that it's validated with our ground-truth and use that to help us inform how much water is being saved and how this change is affecting the hydrology.
Jess: How are you treating the phragmites? Herbicide has been used. What about any other methods, like hand removal or fire?
Paul: Forestry, Fire, and State Land collaborate with The Nature Conservancy, which also has big parcels of land around the lake. They found treatments of herbicide with mastication, so churning up the plant material and cutting it down, doing that for several years in a row, after several iterations of that, they're able to take it out. It's a very hardy plant. Once they know that they've eliminated the phragmites, they can go in and reseed with native species. Other approaches that I've heard of are burning, though there's pluses and minuses with that. I've seen cows used. They'll eat phragmites, but I don't know what amount that has been applied yet. The most common approach is this herbicide and mastication combination, iterated over several seasons.
Jess: Who is going out and do you have enough people, or do you need to involve the community in order to quash all of the phragmites?
Paul: Most of that work is done by Forestry, Fire, and State Land (FFSL), one of the divisions of our department, in collaboration with The Nature Conservancy. They've both been working together. They have a Marsh Master - a tank-like device that can float and drive through this stuff. They'll attach a device that chops things up on the back, and they can just plow it over.
Jess: Wait, so, you just have one of them, the little tank?
Paul: The state owns several. We've been using the one from The Nature Conservancy. They've been kind enough to give us rides to help us transport our station out there, get out there when it's too muddy to drive any kind of vehicle close.
Jess: They have this issue in Las Vegas, where they have phragmites australis, and it does catch fire, and it travels really quickly because it's so dry and the reeds are very flammable. Maybe that's why it's not being used as a treatment technique? It could get out of control if you don't have water. Also, if it's using more ET, it probably has more extensive root systems.
Paul: It's very much like a grass where all of the root system is connected, which is part of what makes it so hardy. You have to pretty much kill off the entire colony of it in order to eliminate it. It has a lot of interconnected roots. So far, our measurements have shown that it pretty much uses as much water as it can get its hands on. Some of the largest amount of ET of any of our sites has been measured at this phragmites site, upwards of 48 inches per year.
Danyal: One reliable and excellent partner that I think we should mention, the USGS. The University of Utah is helping us, and the UGS and Water Resources, we are under the same department. USGS is planning to put buoys in the lake that would help us when we are at the stage that we would put an eddy covariance tower. We will also need the lake profile temperature and related meteorological variables.
Jess: What would be the difference in the Dead Sea system versus this ecosystem?
Danyal: The big difference is the wetlands. So, we have these huge wetlands around the Great Salt Lake. That's not the case in the Dead Sea. Also, no mountains compared to like what we have here. What we have here in the Great Salt Lake is much more complex if we compare it with the Dead Sea, especially in relation to using the eddy covariance systems to measure the evaporation. It is still a very useful study for us. It was done in an environment like a hypersaline environment. They did put a tower inside the sea itself, which was highly challenging, and which is something that we are learning a lot from.
Jess: Was it also focused on common reed?
Paul: I think they were focusing mainly on just measuring ET of a saline system. Salt Lake is complicated because you have an urban-rural interface right up against this very unique ecosystem. There's a lot of different interaction between people and this lake system. In some places, the development comes almost right up against the lake. There's a state park that goes into the lake. It's the namesake of Salt Lake City. The Dead Sea equivalent, I think they were mainly trying to measure just open water.
Danyal: They were just measuring evaporation because it's open water. Nothing related to transpiration or vegetation.
Jess: Maybe you could talk about funding - why is there so much effort around this project? Is this something that people in the state are going out and supporting?
Danyal: I would go back to the Great Salt Lake Basin Integrated Plan, which was the bigger project. It had funding specifically reserved for the evaporation study. The Great Salt Lake Basin Integrated Plan was led by the Division of Water Resources. Now, we are in the stage of [asking] what should we do about measuring the evaporation and evapotranspiration from the lake and the wetlands?
We reached out to our partners at the Utah Geological Survey because the UGS had already been doing these studies using eddy covariance systems around the state, mainly in agricultural fields. We then also reached out to a group at University of Utah led by Professor John Horel. We had the funds, but we were looking for partners who had the experience.
Paul: Besides the wonderful collaborations we've had with the great scientists of Water Resources, and USGS, and the U of U, there's been a lot of really great collaboration with the brine shrimp industry. The mineral pond site is on private property owned by Compass Minerals. They've been an essential collaborator in understanding the ET of the site. They get the benefit of understanding how much evaporation is coming off of their pond. They're also allowing us to share the data and use it to benefit all the people of Utah. We've been doing a lot of work with farmers and agricultural growers. They're just as interested in conserving water while trying to maintain their livelihood.
There's definitely a lot of interest in the rural communities, finding ways to optimize water use and application. In many cases, the amount of water you use equates to how much it costs to produce the product that you're making. It's an important part of business for growers and operators. It's definitely… it can create conflict sometimes, in terms of perception. Understanding where water is going, and where isn't it going is really important, and there's been some important policy changes in terms of water right law, to help give farmers and water right holders tools to benefit the lake and still maintain their livelihood.
Jess: What kind of feedback do you get from these communities?
Paul: It's a broad spectrum of opinions and viewpoints. Generally, it is supportive and cooperative. There's a genuine interest in the data, in understanding how water is moving through these systems. Most of the people I've dealt with are very well-informed. They see the changes in the amount of snowpack. They see the changes in the climate and temperature.
Jess: How should younger scientists get involved in collaborative research with positive public outcomes?
Danyal: This one project is a specific example where you can, like, really talk about the impact. We talked about the U of U team. We have this brilliant graduate student, Misha, who is working on the project. There is a chance to interact with agencies at the state level like Water Resources, UGS, FFSL; at the federal level, the US Geological Survey. Also, contributing to the society as a whole, like, this research has a lot of impact. It's not just related to finding some data and then developing a model and then that's it. It goes beyond that.
Paul: Learning how to summarize the benefits of whatever research they're working on effectively and how that contributes to the big picture is a really good place to start. Look for a common denominator. It's easy for us because a lot of people in Utah care about water. Once you start that conversation with anybody, it's an easy conversation to have. Finding that commonality in the big picture of benefits of that research is a really good place to start.
Jess: Paul, you've been interviewed by Newsweek about your work on evapotranspiration, and Danyal, you have an interest in scicomm as well. [For] young scientists whose work might have some tangible application outside of the scientific realm, how do you get that work out there?
Danyal: With these highly technical things you can publish a paper and it's out there. But, what I really like to see from research is how you can convey what you discover to the general public. There is the importance of science communication. You break it down to that level. Recently, I have been seeing a lot of newspaper articles which are synthesizing the research articles that are coming out. The general public is not reading the journal articles, but they are reading newspapers and the media. I don't think we ourselves will be writing press releases, but do have people here, for example, we have public relations officers.
Paul: Each division in the Department of Natural Resources generally has a point person. It's generally encouraged for us to provide content for social media outreach. I think it's really important, as government employees of the state, to show the people of Utah the value that we bring with their tax dollars and how we're benefiting people. We have to find ways to communicate that value and help them understand technical projects, how they're bringing some kind of return on investment.
Danyal: We also have a social media specialist who is very good at creating these posts of the work that we do. That's also a very good way to communicate. For these eddy covariance measurements that we are doing, there was a lot of interest in the comments. You can see that.
Jess: Do you see people picking up your research findings and writing policy recommendations based on them?
Danyal: The Great Salt Lake Basin Integrated Plan started when the Great Salt Lake hit the lowest level ever in 2022. The funds were made available by the state legislature. So, it was policy that asked the Division of Water Resources to develop this plan. Within this plan, then, we had these multiple projects. Once we have completed our analysis, we publish a report with the recommendation that, “Here is what we discovered: X, Y, and Z. Here is what we think needs to be done.” Again, it goes back resistant legislature and they can make informed decisions.
Jess: When the lake hit its lowest level, how did people find out?
Danyal: We have a very good monitoring network, thanks to the US Geological Survey. They have two points in the lake where they measure water level. It's real-time data from the National Water Information System website of the USGS. So, you can actually look at the lake level every day. Since we have a very long-term record spanning over decades, we know what was in the past and what it is currently. The lowest was in 2022. That was actually a result of the 20-year drought, so that was expected.
Paul: The lake level record goes back to the mid-1800s, not too long after some of the pioneers got here. The National Water Information System, NWIS, is available on USGS' webpage, so anybody can view lake levels over time.
Danyal: The lake has not just economic and ecological significance, but cultural value as well and people do realize it here. Even the name of our city is tied to the lake itself – we are the Salt Lake City. People are really interested in preserving it for the future generations.
Paul: When it comes to state politics, I think it's a non-partisan issue. People see the value in the lake. There have been some pretty significant efforts from the legislature and the government to take action on these rapidly declining lake levels. The governor just recently announced a drought emergency order for the state. It's all tied to management of the water resources here.
Jess: How does the work being done at Lake Powell compare? And then, how are you expecting your results to vary based on water depth, salinity, and heat distribution?
Paul: Lake Powell is different in the sense that they had a pontoon setup with flux measuring devices. They're using IRGASONs (infrared gas analyzer (IRGA) and sonic anemometer (SON)) or something similar. They have a depth profile of temperature where you can see an attenuation of temperature response with depth. They were able to measure heat transfer. That's a similar approach that the USGS is attempting with these buoys. They also did work in Bear Lake on the boundary between Idaho and Utah.
The Great Salt Lake is complicated because, near the edges of the lake, the lake gets deeper very slowly. You can walk very far before you're in over your head. The lake is actually split into two different major parts. There's the north arm, which is much saltier, and then the south part of the lake. So, there's all these different things to account for, and that's part of what spurred this pilot study. [In] some places it's 20 feet deep. You're gonna put a bunch of metal, metallic instruments in a very, very salty environment. Just see how they hold up. How are we going to get to those lenses and clean those lenses? [These are] logistics that we just have to think about.
Danyal: When we were working on the proposal, we reached out to the group who did the Dead Sea evaporation study. We had a similar idea, like, putting one tower in the lake and one offshore. They sent us some images of these huge salt deposits on their instruments. It's challenging enough to do it in a water body, but it's even more challenging to do it in a saline water body. In our mind, we started with the simpler ones, the playa, the wetlands, and the mineral ponds.
Paul: The idea with a platform in the lake is that that could be a research hub where multiple agencies can equip whatever they need to based on what research they're working on; hydrology, lake ecology, salinity. We have a group who study minerals. Depending on the temperature and the lake level, they could be solid or dissolved. There's recent interest in lithium, which also exists in the lake in some concentration. So, understanding all these different things, having central hub would be really beneficial.
Jess: Would you expect that there would be some photosynthesis happening in the lake?
Danyal: I would be surprised if there is any known vegetation that could survive in this highly saline environment.
Paul: There is some duckweed in the paths that we've cleared. The only thing I think that might photosynthesize in the lake is microbialites.
Jess: Are you measuring methane?
Paul: At the phragmites site we're measuring methane and CO2, and then we also are collaborating with a researcher at Brigham Young University. She's looking at the microbial diversity in the soil and how that changes with treatment. The instrument that we're using is a loaner instrument from the AmeriFlux Network.
Jess: The AmeriFlux Loaner Program can also help people who have lost an instrument due to a lightning strike while they're waiting for a replacement, so they don't have a huge gap in data. What aspects of this work are most important to communicate with the public? I was thinking: not growing phragmites australis in their garden, cleaning off their shoes, emptying out their ballast water.
Paul: There are marinas. Water Resources has some really great programs in terms of preserving and conserving water and municipalities.
Danyal: We have conservation programs where there is an incentive if you can transform your traditional landscape into a water-wise landscape. That's not directly related to the lake or the wetlands. You can still argue that it is still related. Like, we want to conserve as much water as we can, because then it ultimately goes to the lake.
Jess: So, you're talking about groundwater recharge from nearby residential areas, [that it potentially] could help improve the status of the lake water. Is there monitoring of groundwater.
Danyal: The USGS does that. We have the water pumpage data for various uses like M&I and irrigation and water level data. One recent endeavor of the USGS, they are developing a MODFLOW model for the Great Salt Lake Basin. They are doing a lot of stuff related to the groundwater.
Paul: There's also been a lot of work by the University of Utah and Utah Geological Survey to measure the lake bed, shallow groundwater tied to these shallow aquifers, because there's a lot of interest in understanding the amount of groundwater contribution and how much diffuse flow there might be occurring through the lake bed, and just understanding the subsurface hydrogeology. Is there a big saline lens of groundwater right underneath the lake, how are springs contributing to the lake, trying to quantify that because that's another big question mark.
The USGS has done a great job measuring the inflow of surface water. They've been maintaining a great groundwater level network around the state, but understanding the nuanced flow of groundwater into the lake is still something we are working on. That, with the model that the USGS is doing, should help significantly.
Jess: Are you also having to go around and measure what percent of the plot is covered by phragmites australis, and how that's changing?
Paul: It's so thick that it is a hundred percent of the plot. It is almost impossible to walk through. It is a very unpleasant experience. Part of the UGS is the State Wetland Coordinator Office in our Groundwater & Wetlands Group. They are in charge of mapping out the vegetation around the lake. They have used air photos and a lot of boots-on-the-ground work to map these out so they can assist us in our work with understanding how the vegetation community has changed before and after treatment.
Jess: Are you still waiting for it to be treated?
Paul: Yes. We just have one plot, so before and after measurements at one site.
Jess: When it's treated, are you expecting it to be a mudflat for a little bit?
Paul: There's some question of whether they're going to remove the litter from the treated material or not. There's been some studies that show eliminating some of that will help reinstate the natural plants. They're also doing a lot of impoundments adjacent to this site, which is another way to mitigate areas by flooding. We're just going to bag the tower right before treatment to make sure it isn't contaminated with the herbicide.
Jess: What data is already available from this study?
Paul: I think it'll take some time. We're generally kind of slow-moving when it comes to getting stuff published. There will be a thesis from the U coming out soon related to this work. We release our data as soon as we can. We make it available on our website. It's preliminary, obviously, and then we refine it and publish on it is quickly as we can. Maintaining such a large network of this many flux sites, it's always a balance between doing the fieldwork and doing the research. And, we've been doing cradle to grave for all of that. It delays some of our research that we really want to be attacking.
Danyal: The playa station and the Compass Mineral station, the final report, and the data, everything, should be available and ready by January 2026.
Jess: For people who don't know what a playa is, it's an area of flat, dried up land, especially a desert basin, from which water evaporates quickly.
Danyal: When the lake level rises up, you can see that station submerged, and when the lake recedes, it is dry.