How lakes connect to groundwater critical for resilience to climate change, research finds

(Press-News.org) 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.

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