Predicting river flow dynamics using stable isotopes to improve ecosystem health

An international scientific team has made significant progress in understanding the dynamics of river flow. The results leverage isotope hydrology techniques such as measuring stable isotopes in water molecules to elucidate the contributions of various water sources to river flow, providing essential information for ecosystem management and hydrological risk assessment.

This latest research is published in Natural water and is a collaboration of scientists from the German Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) with the International Atomic Energy Agency (IAEA), the Federal Institute of Hydrology of Germany and Stellenbosch University in South Africa.

The international scientific team analyzed stable isotopes of oxygen and hydrogen in water molecules from 136 perennial rivers and 45 large watersheds around the world. Dr. David Soto, scientist and isotope specialist at Leibniz-IZW, contributed to the modeling of precipitation isotope data and their validation for the calculation of the dynamic water retention indicator, essential for representing flow dynamics fluvial. Water retention describes the retention, storage and distribution of precipitation.

High dynamic water retention indicates slow movement of water through watersheds, suggesting a slower response to hydroclimatic events. In contrast, low dynamic water retention means rapid movement of water and a much faster response to such events. The team identified key factors influencing dynamic water retention, including land-use changes (such as vegetation and forest cover) and climate changes (such as air temperature and precipitation ). These factors significantly affect the way water moves in river watersheds, affecting the “age” of river water and their overall dynamics.

“By using models to predict precipitation isotope data, we were able to accurately calculate the dynamic water retention indicator, a crucial tool for understanding river flow dynamics,” says Soto. “Our validation of these models ensures their reliability, providing valuable information on how climate change and land use patterns affect river systems. Monitoring stable isotopes in natural hydrological systems is essential for predicting and mitigating hydrological risks in order to improve the management of our natural resources.

Rivers are essential in supporting various ecosystem services. They nourish riverine animal and plant communities, provide essential nutrients to the marine environment, provide transportation routes for commerce, generate hydroelectric power, and provide recreational opportunities. Even during dry periods, rivers often continue to flow, due to the contribution of several sources, including direct precipitation, surface runoff, intercircular flow through the ground, and base flow of groundwater.

Climate change and land use changes are significantly altering the movement of water in river catchments, thereby affecting the “age” of river water. This phenomenon, related to the aging of rivers, has profound implications on the services provided by rivers. For example, low levels of the Rhine during the European summer of 2023 disrupted the movement of goods and services as conventional vessels could no longer move, highlighting the crucial need to understand these dynamics.

Watersheds with low dynamic water retention are more susceptible to hydrological extremes such as droughts and floods. Therefore, dynamic water retention constitutes a crucial indicator for hydrological risk assessment, contributing to the prediction and mitigation of climate and land-use change impacts on river systems.

It is essential to ensure that rivers continue to provide their essential services to ecosystems and human societies. By understanding and monitoring the dynamics of water retention and flows, it will become easier to adapt and manage the challenges posed by climate change and changing land use patterns.