Dams, Not Just Climate, Drive Tigris Water Loss
A four-decade study finds human interventions cause 39.3% of basin degradation, with a 10 billion cubic meter deficit projected by 2035.
Updated on Nov. 2, 2026 in Environmental
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A study led by Dr. Ali Darvishi Bolourani of the University of Tehran, with Kuwaiti, Italian, and Australian academics, attributes 39.3% of water resource degradation in the Tigris-Euphrates basin to human interventions and 13.6% to climate change. The findings were published in the journal Environmental Science and Policy and are research-stage analysis rather than a policy change.
Why it matters
The researchers integrated multi-source satellite data, hydro-climatic analyses, and water balance equations over four years, examining the basin from 1984 to 2022. The attribution points to dam construction in Turkey, resource management in Iraq, and agricultural expansion as the dominant drivers, which reframes a shared-river crisis that is often discussed mainly as a climate story.
The attribution rests on a four-decade analysis of the basin using satellite and water-balance data, with human interventions measured at 39.3% against 13.6% for climate change. The study reports that upstream reservoir storage more than doubled in thirty years, but it does not separate every contributing factor beyond these two shares.
The players
Dr. Ali Darvishi Bolourani
Lead author and researcher at the University of Tehran who led the study on Tigris-Euphrates water degradation.
University of Tehran
Iranian research university whose team led the multi-country analysis of basin water resources.
Environmental Science and Policy
Peer-reviewed journal that published the study on human and climate drivers of basin water loss.
Southeastern Anatolia Project (GAP)
Turkish regional development program comprising 22 dams and 19 hydroelectric plants on the upper Tigris and Euphrates.
The details
The team combined satellite observations with hydro-climatic models and water balance equations, a method that tracks how much water enters a basin, how much leaves, and how much is stored in between. Turkey's Southeastern Anatolia Project (GAP) includes 22 dams and 19 hydroelectric plants, and upstream reservoirs now hold substantially more water while exposing about 9,500 square kilometers of new evaporation surface. The result is that less water reaches downstream Iraq, Iran, and Syria, even where rainfall patterns have changed only modestly.
Timeline
1984 to 2022: the period of basin evolution analyzed by the researchers.
1990 to 2016: flow of the Tigris and Euphrates into Iraq fell 25%.
2025: Iraq recorded its driest year on record, with reserves below 4 billion cubic meters.
2035: projected water deficit of about 10 billion cubic meters and loss of roughly 25,000 hectares of farmland each year.
The Tech Race
The findings place upstream dam engineering and water allocation at the center of the transboundary water debate, ahead of climate attribution alone. Competing approaches to basin management now have a quantified benchmark to measure against.
Farmers and water managers in Iraq, Iran, and Syria face a projected deficit that the study estimates at about 10 billion cubic meters by 2035. Changes to upstream dam operation and downstream irrigation planning are the practical levers the study points toward, though no specific policy has been announced.
The takeaway
The study frames upstream dam management and agricultural water use as the dominant levers for Tigris-Euphrates recovery rather than climate alone. Readers should watch whether the 2035 deficit projection of roughly 10 billion cubic meters is revised as Iraq's reserves and Turkish reservoir operations are measured in coming seasons.
Further reading
For broader context on river basins and water stress, browse our Environmental coverage.
Source note: This article includes information reported by Tiredearth.
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