Rising temperatures are making Türkiye’s snow-dependent water resources increasingly vulnerable, with earlier snowmelt and more severe warm-dry snow drought threatening water availability, according to a two-year study by Istanbul Technical University (ITU).
The study, which examined snow-dependent basins across Türkiye between 1990 and 2024, found that a shift occurred after 2007 from precipitation-driven snow drought to a period in which temperature became a more influential factor.
Researchers also found that warm and warm-dry snow droughts have become more widespread, with the latter emerging as the most severe type across the basins studied.
The study was led by Dr. Harun Aslan under the supervision of Prof. Dr. Tolga Görüm and Associate Professor Abdullah Akbaş of ITU, with contributions from Assistant Professor Seçkin Fidan of Ankara University.
Researchers analyzed 15 of Türkiye’s 25 major basins, including the Çoruh, Eastern Black Sea, Aras, Yeşilırmak, Lake Van, Euphrates-Tigris, Seyhan, Kızılırmak, Ceyhan, Sakarya, Eastern Mediterranean, Konya and Susurluk basins.
The study classified snow drought into three types: dry snow drought caused by reduced precipitation, warm snow drought caused by higher temperatures shifting precipitation from snow to rain, and warm-dry snow drought caused by both reduced precipitation and rising temperatures.
Warm-dry snow drought affected 13% of the study area on an annual average and was observed in all 15 basins examined. Its affected area increased after 2007, while the area experiencing dry snow drought declined.
The study found that snowmelt accounts for an average 44.7% of long-term runoff in the examined basins, highlighting the importance of snow cover for Türkiye’s water resources.
Runoff declined by 36% during warm-dry snow drought years, with the effects particularly pronounced at lower elevations. Researchers found that snow water equivalent losses were greatest below 2,000 meters.
Warm-dry snow drought was the most severe type identified in the study and carried the highest frequency and risk in 14 of the 15 basins.
Akbaş said the shift toward temperature-driven snow drought means water management must focus not only on how much water is available but also on when it becomes available.
"It’s no longer only about how much water we have, but also when that water is available for use,” he said.
Rising temperatures can cause more winter precipitation to fall as rain instead of snow or cause snow cover to melt earlier, allowing water to leave the natural snow reservoir sooner. Akbaş warned that this could make water management more difficult in late spring and summer, when demand for water increases.
He added that the combination of higher temperatures and reduced precipitation could intensify drought, reduce water reaching reservoirs and negatively affect hydroelectric power generation.
Aslan described snow cover as a natural reservoir that carries water from winter into the summer months, stressing that its importance should be assessed not only by how much snow falls but also by when it melts.
"Snow drought is not only about how much snow falls, but also how long the snow can store water,” he said.
Aslan called for closer monitoring of snow cover changes in snow-dependent basins to improve water supply planning, irrigation and reservoir management.