The Caspian Sea is the world’s largest endorheic water body and has experienced substantial fluctuations in water level during the twentieth and twenty-first centuries. Recent climate projections indicate that increasing temperature, enhanced evaporation, and changes in riverine inflow may intensify the long-term decline in Caspian Sea level. This study builds on the mathematical and geometrical framework presented by Ghorbani (2025) for assessing shoreline and geometric changes along Iran’s Mazandaran coast and applies a 3-m water-level decline by 2035 as a regional scenario for the entire Caspian Sea. The main objectives are to estimate the potential changes in the total surface area and water volume of the Caspian Sea and to assess the potential consequences for coastal geometry, navigation, ports, and offshore oil and gas infrastructure in the five littoral states: Iran, Kazakhstan, Russia, Turkmenistan, and Azerbaijan. The present Caspian Sea surface area is approximately 389,000 km2 and its volume is approximately 78,000 km3. Because the relationship between water level and surface area is strongly nonlinear, a 3-m decline cannot be converted into an area loss using a simple linear relationship. Nevertheless, historical observations and recent bathymetric studies suggest that a decline of this magnitude could result in the loss of several tens of thousands of square kilometers of water surface, particularly in the shallow northern Caspian. In this study, an initial scenario range of approximately 30,000-45,000 km2 of surface-area loss is proposed, while the corresponding reduction in water volume is estimated at approximately 1,000-1,200 km3. The consequences are not spatially uniform. Kazakhstan and Russia are expected to face the greatest direct risks to shallow-water offshore energy infrastructure because of fields such as Kashagan and Vladimir Filanovsky. Turkmenistan may also face substantial risks because of offshore developments in the Cheleken area and the shallow eastern Caspian. In Azerbaijan, major fields such as Azeri-Chirag-Gunashli are located in considerably deeper waters, making their direct exposure to a 3-m reduction relatively limited; however, ports, coastal terminals, navigation routes, and logistics infrastructure may be affected. In Iran, the principal impacts are expected to involve shoreline retreat, ports, wetlands, fisheries, tourism, and coastal infrastructure rather than large-scale offshore hydrocarbon production. The results indicate that a 3-m decline, although substantially smaller than the 8-14 m best-fit projections and the upper-end projections of up to 21 m by the end of the twenty-first century, should be considered an important early-warning scenario for regional infrastructure and energy planning. The study further demonstrates the potential value of extending the mathematical shoreline framework developed by Ghorbani (2025) toward a basin-wide model of energy-infrastructure vulnerability.
| Published in | Hydrology (Volume 14, Issue 3) |
| DOI | 10.11648/j.hyd.20261403.12 |
| Page(s) | 64-71 |
| Creative Commons |
This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited. |
| Copyright |
Copyright © The Author(s), 2026. Published by Science Publishing Group |
Caspian Sea, Water-level Decline, Shoreline Retreat, Oil and Gas, Offshore Infrastructure, Mathematical Modeling, Climate Change
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| [2] | Samant, R., & Prange, M. (2023). Climate-driven 21st century Caspian Sea level decline estimated from CMIP6 projections. Communications Earth & Environment, 4, 357. |
| [3] | Court, R., Lattuada, M., Shumeyko, N., et al. (2025). Rapid decline of Caspian Sea level threatens ecosystem integrity, biodiversity protection, and human infrastructure. Communications Earth & Environment, 6, 261. |
| [4] | Chen, J. L., Pekker, T., Wilson, C. R., et al. (2017). Long-term Caspian Sea level change. Geophysical Research Letters. |
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| [6] | Moradi, M., et al. (2020). Impacts of variations in Caspian Sea surface area on catchment hydroclimate. Journal of Geophysical Research: Atmospheres. |
| [7] | Akbari, M., Baubekova, A., Roozbahani, A., et al. (2020). Vulnerability of the Caspian Sea shoreline to changes in hydrology and climate. Environmental Research Letters. |
| [8] | Lahijani, H. A. K., et al. (2023). Tracking of sea level impact on Caspian Ramsar sites and potential restoration of the Gorgan Bay on the southeast Caspian coast. Science of the Total Environment. |
| [9] | De Smedt, M., et al. (2025). Data-driven resilience analysis of dynamic port operations at the Amir-Abad port (Iran). Journal of Imaging. |
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| [11] | Rabbani, A. I., Al-Hajri, S., Hussain, K. S., et al. (2023). Reservoir characterization of the Pliocene Red Series, LAM field and surrounding areas, offshore western Turkmenistan. Journal of Petroleum Geology, 46(1), 77-102. |
| [12] | Oppo, D., Capozzi, R., Nigarov, A., et al. (2014). Mud volcanism and fluid geochemistry in the Cheleken peninsula, western Turkmenistan. Marine and Petroleum Geology, 57, 122-134. |
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| [15] | Huang, G., et al. (2021). Caspian Sea and Black Sea Response to Greenhouse Warming in a High-Resoloution Global Climate Model. Geophysical Research Letters, 48(11). |
APA Style
Ghorbani, M. (2026). Caspian Sea Level Decline by 2035: Mathematical and Regional Assessment. Hydrology, 14(3), 64-71. https://doi.org/10.11648/j.hyd.20261403.12
ACS Style
Ghorbani, M. Caspian Sea Level Decline by 2035: Mathematical and Regional Assessment. Hydrology. 2026, 14(3), 64-71. doi: 10.11648/j.hyd.20261403.12
AMA Style
Ghorbani M. Caspian Sea Level Decline by 2035: Mathematical and Regional Assessment. Hydrology. 2026;14(3):64-71. doi: 10.11648/j.hyd.20261403.12
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Download@article{10.11648/j.hyd.20261403.12,
author = {Majid Ghorbani},
title = {Caspian Sea Level Decline by 2035: Mathematical and Regional Assessment},
journal = {Hydrology},
volume = {14},
number = {3},
pages = {64-71},
doi = {10.11648/j.hyd.20261403.12},
url = {https://doi.org/10.11648/j.hyd.20261403.12},
eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.hyd.20261403.12},
abstract = {The Caspian Sea is the world’s largest endorheic water body and has experienced substantial fluctuations in water level during the twentieth and twenty-first centuries. Recent climate projections indicate that increasing temperature, enhanced evaporation, and changes in riverine inflow may intensify the long-term decline in Caspian Sea level. This study builds on the mathematical and geometrical framework presented by Ghorbani (2025) for assessing shoreline and geometric changes along Iran’s Mazandaran coast and applies a 3-m water-level decline by 2035 as a regional scenario for the entire Caspian Sea. The main objectives are to estimate the potential changes in the total surface area and water volume of the Caspian Sea and to assess the potential consequences for coastal geometry, navigation, ports, and offshore oil and gas infrastructure in the five littoral states: Iran, Kazakhstan, Russia, Turkmenistan, and Azerbaijan. The present Caspian Sea surface area is approximately 389,000 km2 and its volume is approximately 78,000 km3. Because the relationship between water level and surface area is strongly nonlinear, a 3-m decline cannot be converted into an area loss using a simple linear relationship. Nevertheless, historical observations and recent bathymetric studies suggest that a decline of this magnitude could result in the loss of several tens of thousands of square kilometers of water surface, particularly in the shallow northern Caspian. In this study, an initial scenario range of approximately 30,000-45,000 km2 of surface-area loss is proposed, while the corresponding reduction in water volume is estimated at approximately 1,000-1,200 km3. The consequences are not spatially uniform. Kazakhstan and Russia are expected to face the greatest direct risks to shallow-water offshore energy infrastructure because of fields such as Kashagan and Vladimir Filanovsky. Turkmenistan may also face substantial risks because of offshore developments in the Cheleken area and the shallow eastern Caspian. In Azerbaijan, major fields such as Azeri-Chirag-Gunashli are located in considerably deeper waters, making their direct exposure to a 3-m reduction relatively limited; however, ports, coastal terminals, navigation routes, and logistics infrastructure may be affected. In Iran, the principal impacts are expected to involve shoreline retreat, ports, wetlands, fisheries, tourism, and coastal infrastructure rather than large-scale offshore hydrocarbon production. The results indicate that a 3-m decline, although substantially smaller than the 8-14 m best-fit projections and the upper-end projections of up to 21 m by the end of the twenty-first century, should be considered an important early-warning scenario for regional infrastructure and energy planning. The study further demonstrates the potential value of extending the mathematical shoreline framework developed by Ghorbani (2025) toward a basin-wide model of energy-infrastructure vulnerability.},
year = {2026}
}
TY - JOUR T1 - Caspian Sea Level Decline by 2035: Mathematical and Regional Assessment AU - Majid Ghorbani Y1 - 2026/09/28 PY - 2026 N1 - https://doi.org/10.11648/j.hyd.20261403.12 DO - 10.11648/j.hyd.20261403.12 T2 - Hydrology JF - Hydrology JO - Hydrology SP - 64 EP - 71 PB - Science Publishing Group SN - 2330-7617 UR - https://doi.org/10.11648/j.hyd.20261403.12 AB - The Caspian Sea is the world’s largest endorheic water body and has experienced substantial fluctuations in water level during the twentieth and twenty-first centuries. Recent climate projections indicate that increasing temperature, enhanced evaporation, and changes in riverine inflow may intensify the long-term decline in Caspian Sea level. This study builds on the mathematical and geometrical framework presented by Ghorbani (2025) for assessing shoreline and geometric changes along Iran’s Mazandaran coast and applies a 3-m water-level decline by 2035 as a regional scenario for the entire Caspian Sea. The main objectives are to estimate the potential changes in the total surface area and water volume of the Caspian Sea and to assess the potential consequences for coastal geometry, navigation, ports, and offshore oil and gas infrastructure in the five littoral states: Iran, Kazakhstan, Russia, Turkmenistan, and Azerbaijan. The present Caspian Sea surface area is approximately 389,000 km2 and its volume is approximately 78,000 km3. Because the relationship between water level and surface area is strongly nonlinear, a 3-m decline cannot be converted into an area loss using a simple linear relationship. Nevertheless, historical observations and recent bathymetric studies suggest that a decline of this magnitude could result in the loss of several tens of thousands of square kilometers of water surface, particularly in the shallow northern Caspian. In this study, an initial scenario range of approximately 30,000-45,000 km2 of surface-area loss is proposed, while the corresponding reduction in water volume is estimated at approximately 1,000-1,200 km3. The consequences are not spatially uniform. Kazakhstan and Russia are expected to face the greatest direct risks to shallow-water offshore energy infrastructure because of fields such as Kashagan and Vladimir Filanovsky. Turkmenistan may also face substantial risks because of offshore developments in the Cheleken area and the shallow eastern Caspian. In Azerbaijan, major fields such as Azeri-Chirag-Gunashli are located in considerably deeper waters, making their direct exposure to a 3-m reduction relatively limited; however, ports, coastal terminals, navigation routes, and logistics infrastructure may be affected. In Iran, the principal impacts are expected to involve shoreline retreat, ports, wetlands, fisheries, tourism, and coastal infrastructure rather than large-scale offshore hydrocarbon production. The results indicate that a 3-m decline, although substantially smaller than the 8-14 m best-fit projections and the upper-end projections of up to 21 m by the end of the twenty-first century, should be considered an important early-warning scenario for regional infrastructure and energy planning. The study further demonstrates the potential value of extending the mathematical shoreline framework developed by Ghorbani (2025) toward a basin-wide model of energy-infrastructure vulnerability. VL - 14 IS - 3 ER -
Department of Mathematics, Azad University, Tehran, Iran
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