University of Granada researchers have deployed the first floating platform with eddy covariance technology in Spain to continuously monitor greenhouse gas emissions from a reservoir—revealing critical climate vulnerabilities.

The eddy covariance (also known as eddy correlation and eddy flux) is a key atmospheric measurement technique to measure and calculate vertical turbulent fluxes within atmospheric boundary layers. The method analyses high-frequency wind and scalar atmospheric data series, gas, energy, and momentum, which yields values of fluxes of these properties. It is a statistical method used in meteorology and other applications (micrometeorology, oceanography, hydrology, agricultural sciences, industrial and regulatory applications, etc.) to determine exchange rates of trace gases over natural ecosystems and agricultural fields, and to quantify gas emissions rates from other land and water areas. It is frequently used to estimate momentum, heat, water vapour, carbon dioxide and methane fluxes.

Continental aquatic ecosystems occupy less than 2 percent of Earth‘s surface yet generate 40-50 percent of global methane emissions. However, uncertainty about their true greenhouse gas output has persisted because most data comes from one-off, point-in-time measurements that miss crucial patterns.

That changed when an interdisciplinary team from the University of Granada installed a measurement tower on a floating platform in the Cubillas reservoir. For the first time in Spain, the installation uses eddy covariance technology—a sophisticated micrometeorological technique—to continuously measure carbon dioxide and methane emissions from water surfaces.

Key Findings with Alarming Implications

Over two years spanning diverse hydrological conditions, researchers discovered that methane emissions spike dramatically during droughts when water levels drop. Lower water accelerates biogeochemical processes in sediments, intensifying methane production and bubbling.

Carbon dioxide emissions remained stable, but methane fluctuated unpredictably—changing abruptly over hours or days in patterns that traditional sampling completely missed. Wind speed and eutrophication amplified these swings.

“The detected daily fluctuations and episodic emission events would be invisible with conventional methods,” the research team noted.

Climate Urgency

Methane’s global warming potential is 80 times stronger than carbon dioxide over 20 years—making even small emission increases significant. Mediterranean reservoirs face a compounding crisis: climate projections show increasing droughts and intensifying eutrophication, both of which dramatically boost methane release.

Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; i.e. the process of too many plants growing on the surface of a river, lake, etc., often because chemicals that are used to help crops grow have been carried there by rain.

Published in Global Change Biology, the research warns that Mediterranean reservoirs could substantially amplify greenhouse gas contributions under future climate scenarios, reinforcing their role as accelerating climate threat rather than climate-neutral infrastructure.

With nearly 90 percent of Earth’s rivers projected to have dams by mid-century, understanding and controlling reservoir emissions is now urgent for climate policy.