How lakes connect to groundwater critical for resilience to climate change, research finds
Research presented at the Goldschmidt Conference in Prague
European Association of Geochemistry
image:
Rimov reservoir in the Czech Republic.
view moreCredit: Petr Znachor
Understanding whether lakes are fed predominantly by groundwater or rainwater is critical to managing our water resources in the face of droughts and shortages, new research has found.
The study drew on data from 350 lakes across 18 European countries, collected between 2022 and 2024, to provide a comprehensive picture of how the continent’s lakes are coping with climate change. The research is presented today [Wednesday 9 July, 2025] at the Goldschmidt Conference in Prague.
The researchers, from the Czech Academy of Sciences, analysed the proportions of stable hydrogen and oxygen isotopes (18O and 2H) in the lakes’ water. These isotopic signatures help reveal the influence of rainfall, assess the potential connection between groundwater and lakes, and determine the extent to which incoming water offsets losses from evaporation.
The team combined these variables with open access environmental data, including meteorological variables (mean annual temperature and precipitation, climate type, relative humidity), percentage of land use (bare land, cropland, forest, grassland, snow, urban), and catchment characteristics (lake type, size, maximum depth and altitude). Using a machine learning model, they identified the key factors sustaining a healthy water balance for each lake and predicted the impact in 2050 of changes in rainfall and temperature linked to climate change.
The study found that lakes with high potential connection from groundwater maintain more stable water levels and are more likely to be able to buffer the impacts of climate change. Shallow lakes, which tend to have a high surface area in relation to their volume, experience high evaporation rates compared to inflow, making them more vulnerable to rising temperatures and reduced rainfall.
The modelling highlighted that lakes in lowland areas are the most likely to reach critical evaporation to inflow ratios by 2050, leading to water scarcity and contamination, with artificial lakes such as reservoirs most at risk. This is because lakes in lowland areas tend to be shallower and often less connected to groundwater, which destabilises the balance between evaporation and inflow. Additionally, these lakes are more likely to be located in regions of intensive agriculture, where runoff from fertilizers and other inputs can lead to elevated nutrient levels and degraded water quality.
Lakes in higher-altitude or alpine areas were found to be most resilient, benefiting from lower temperatures, reduced evaporation rates, and often better connections to groundwater inflow. These lakes are currently less exposed to surrounding agricultural activity and so face fewer issues related to nutrient runoff. However, the researchers caution that agricultural land use is migrating to higher altitude, which could affect the water quality and availability of these lakes in the future.
Dr Ma. Cristina Paule-Mercado, from the Biology Centre, at the Czech Academy of Sciences, is presenting the research at the Goldschmidt Conference. She said: “We initially expected the same controlling factors to apply across all lakes, but that wasn't the case. While we can draw some general insights from the analysis, we also observed how each region has different dynamics driven by the interaction of multiple variables. This highlights the importance of considering all these factors – and particularly groundwater-lake connectivity – when designing sustainable management strategies to address climate change and water scarcity.”
The team continues to expand their dataset – now incorporating over 400 lakes – with an ambition to make this a global resource. While some of the environmental data come from open-access sources, the researchers also collect samples annually from hundreds of lakes, collaborate with other scientists, an engage in citizen science initiatives. These efforts help broaden their coverage and strengthen community involvement.
The Goldschmidt Conference is the world’s foremost geochemistry conference. It is a joint congress of the European Association of Geochemistry and the Geochemical Society (US), and over 4000 delegates attend. It takes place in Prague, Czech Republic, from 6-11 July 2025.
WSU study provides detailed look at the declining groundwater in regional aquifer system
Washington State University
PULLMAN, Wash. -- Groundwater is declining across Eastern Washington’s complex, interconnected aquifer system, as people draw on it for irrigation, drinking and other uses at a pace that threatens its sustainability, according to a new study by a Washington State University researcher.
In certain “hot spots” – such as the Odessa region and the Yakima Basin – the rates of decline are particularly significant, with groundwater levels dropping two to three feet a year or more.
The data is built upon a new metric of water vulnerability; rather than simply calculating how much groundwater there is, it measures how much is actually accessible with current wells.
“With these numbers we can say, ‘Hey, this is a problem now,’” said Sasha McLarty, an assistant professor in the Department of Civil and Environmental Engineering at WSU and the corresponding author of the new study. “It’s not a problem in the future, it’s a problem now.”
The research, published in the journal Groundwater for Sustainable Development, provides a detailed new picture of the Columbia Plateau Regional Aquifer System. Although not all areas in the system showed declines, the study lends urgency to the need for increased water supplies, for example through water conservation, additional use of surface water, and aquifer-recharging projects.
The paper focuses on a little-studied element of the aquifer system – its variability in both geographic location and depth below the surface. The system underlies the Columbia River Basin in Washington, Idaho and Oregon, providing a quarter to a third of irrigation water across the region.
It is comprised of four main geological layers—three basalt layers formed at different periods in history, and a top layer of sedimentary materials.
“Imagine a layer cake, where you have these chunks of actual cake, which is mostly fractured basalt in this case, and then there’s frosting in between, the parts where water moves more easily,” McLarty said. “That’s our aquifer.”
Unlike a layer cake, however, the layers don’t sit atop each other in a neat, orderly pattern.
“From location to location, that layering looks different,” she said. “Our paper is the first to really quantify that variability, based on observations, in both trends in water level and vulnerability across the entire aquifer.”
Previous groundwater studies have compared the rate of water usage with the volume of water in the aquifer layers, a metric known as saturated thickness. But a lot of that water lies below the depth of current wells. McLarty’s paper measures the water accessible to the current well infrastructure, which they define as available drawdown (ADD), and is a more useful metric to assess how vulnerable groundwater users may be to declines.
“If you have groundwater 15,000 feet deep, that doesn’t help anybody,” McLarty said.
Using state Department of Ecology data collected from nearly 3,000 wells drawing water from the aquifers, researchers calculated trends in the four aquifer layers. The thickest basalt layer—known as the Grand Ronde—had the steepest declines in groundwater, at 1.86 feet per year on average and up to about 7 feet per year. The top layer of sedimentary materials, known as the Overburden layer, had the smallest annual decreases, at 0.22 feet per year.
But the Overburden layer is still vulnerable because it has less available drawdown, the study shows.
Most but not all are in decline
McLarty focused on 15 geographic subareas within the state, which highlighted the points of greatest concern. One of these is the Odessa area in Eastern Washington, which is on a pace to consume 10% of available drawdown by 2040—and half within 70 years.
Wells in the Yakima Basin showed a similar trend to those in Odessa, and most subareas showed a pattern of declining groundwater. However, not every area did. The Spokane Aquifer is gaining water, one of three subareas with a positive trend. McLarty said that this is thanks to very active management and monitoring efforts, including a designated Aquifer Protection Area. Other areas are more complex with some layers declining and some increasing even in the same area, like in the Rock Glade Water Resources Inventory Area. The study shows that you can’t just view groundwater as a single bucket.
McLarty hopes that the new research will encourage efforts to improve groundwater sustainability.
“What I care about most is will people and ecosystems have groundwater in the future to the extent that they need it?” she said. “I hope these data can be used to help prioritize investments in improving water security, by showing where that effort is needed.”
McLarty partners with conservation districts in the aquifer area for groundwater monitoring. If you are interested in having your groundwater monitored, please reach out to McLarty (sasha.richey@wsu.edu) to learn more.
Journal
Groundwater for Sustainable Development
Method of Research
Data/statistical analysis
Article Title
Variations in vulnerability across aquifer layers in a heterogeneous aquifer system
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