The Shrinking Caspian Sea: Eco-Hydrological Responses to Human and Climate Pressures

Authors

• Jesse Duku, Samueli School of Engineering
• Mohammad J. Tourian, Universität Stuttgart
• Marzi Azarderakhsh, New York City College of Technology
• Rovshan Abbasov, Khazar University
• Ali Mehran, San Jose State UniversityFollow
• Ali Torabi Haghighi, Oulun Yliopisto
• Stefanos Xenarios, Commonwealth Scientific and Industrial Research Organisation
• Azara Boschee, Samueli School of Engineering
• Salih Babagiray, Samueli School of Engineering
• Mojtaba Sadegh, Boise State University
• Nima Shokri, Hamburg University of Technology
• Ali Nazemi, Concordia University
• Alireza Farahmand, California State University, Los Angeles
• Samaneh Ashraf, University of Montreal
• Temur Khujanazarov, Disaster Prevention Research Institute
• Elmira Hassanzadeh, United Nations University Institute for Water
• Dalal Najib, National Academies of Sciences, Engineering, and Medicine
• Daniel Placht, National Academies of Sciences, Engineering, and Medicine
• Shamshagul Mashtayeva, Farabi University
• For full author list, see comments below

Publication Date

6-5-2026

Document Type

Article

Publication Title

Earth S Future

Volume

14

Issue

6

DOI

10.1029/2025EF008028

Abstract

The Caspian Sea, the Earth's largest inland water body, faces water level decline, drawing comparisons to the collapse of the Aral Sea. Unlike the Aral Sea, the relative roles of climatic variability, hydrological changes, and anthropogenic pressures on the Caspian Sea remain poorly understood. Here, we integrate satellite observations, in situ hydrological records and reanalysis data to examine recent drivers of the Caspian water loss. We show that total river inflow to the Caspian Sea has declined significantly, primarily due to reduced discharge from the Volga River. At the same time, precipitation over the basin has remained broadly stable, while evaporation over the sea has shown a modest upward trend. These findings point to compound anthropogenic and climatic influences on the regional water balance. We also detect a long-term increase in chlorophyll-a concentrations in the shallow Northern Caspian, signaling growing ecological stress associated with ongoing hydrological change. Avoiding further ecological disruption requires coordinated international action and policies to mitigate shrinkage by optimizing water allocation and environmental releases, as well as prioritizing long-term ecosystem resilience. Without urgent intervention, the Caspian Sea risks following the trajectory of other desiccating inland water bodies, with long-lasting ecological and socioeconomic consequences.

Funding Number

2114701

Funding Sponsor

National Science Foundation

Keywords

anthropogenic water use, Caspian Sea, climate variability, inland water bodies, water level decline

Comments

Full author list:

Jesse Duku, Mohammad J. Tourian, Marzi Azarderakhsh, Rovshan Abbasov, Ali Mehran, Ali Torabi Haghighi, Stefanos Xenarios, Azara Boschee, Salih Babagiray, Mojtaba Sadegh, Nima Shokri, Ali Nazemi, Alireza Farahmand, Samaneh Ashraf, Temur Khujanazarov, Elmira Hassanzadeh, Dalal Najib, Daniel Placht, Shamshagul Mashtayeva, Ekaterina Rets, Hamid Norouzi, Kaveh Madani, Manoochehr Shirzaei, Hossein Shafizadeh-Moghadam, Chiyuan Miao, Ali Mirchi, Shuo Wang, Amir AghaKouchak

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Civil and Environmental Engineering

Recommended Citation

Duku, J., Tourian, M. J., Azarderakhsh, M., Abbasov, R., Mehran, A., Haghighi, A. T., et al. (2026). The shrinking Caspian Sea: Eco-hydrological responses to human and climate pressures. Earth's Future, 14, e2025EF008028. https://doi.org/10.1029/2025EF008028