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Water levels in five of Istanbul’s 10 main reservoirs have dropped below 20% capacity amid a sharp decline in rainfall in Türkiye’s Marmara region this year. According to the Istanbul Water and Sewerage Administration (ISKI), the city’s overall reservoir fill rate has fallen to 20.29% as of Nov. 21, marking the lowest level recorded in the last five years for this period.
The data shows a concerning trend, reflecting both regional rainfall deficits and increasing water demand. Storage volumes at individual reservoirs were measured as follows: Istrancalar at 20.78%, Terkos at 22.61%, Sazlıdere at 19.76%, Alibey at 12.5%, Büyükçekmece at 22.13%, Ömerli at 17.83%, Darlık at 22.99%, Elmalı at 50.68%, Pabuçdere at 3.89%, and Kazandere at a critically low 1.97%.
The city’s reservoirs and ponds collectively have a maximum water storage capacity of approximately 868.7 million cubic meters (229.5 billion gallons), but currently hold only about 176 million cubic meters of water, raising concerns over sustainability if dry conditions persist.
Historical data from ISKI reveals reservoir levels on Nov. 21 over the past decade have generally been higher. The fill rate was 35.27% in 2016, peaked at 55.09% in 2017, and was 48.61% in 2018. Since then, the levels have shown a downward trajectory with rates recorded at 37.13% in 2019, 26.43% in 2020, 41.95% in 2021, 35.4% in 2022, 23.08% in 2023, 27.49% in 2024 and culminating in today’s 20.29%.
Among the reservoirs, Kazandere has experienced the most drastic decline, dropping from 7.85% at this time last year to just 1.97% now. Similarly, Pabuçdere’s fill rate fell from 5.26% last year to 3.89%, and Sazlıdere’s dropped sharply from 38.53% to 19.76%. Terkos Reservoir’s level decreased from 35.14% in 2023 to 22.61% this year. In contrast, Elmalı Reservoir has shown a slight increase from 49.9% last year to 50.68%, and Alibey rose from 6.45% to 12.5%.
Istrancalar’s water level has halved, dropping from 40.52% last year to 20.78% today. Darlık Reservoir showed a marginal decline, from 29.38% to 28.99%. Ömerli Reservoir’s fill rate plunged from 24.85% to 17.83%, marking the lowest level recorded there in the past decade.
Dr. Güven Özdemir, meteorology engineer and faculty member at Istanbul Aydın University, emphasized that the drought affecting Türkiye has been evident since April, with rainfall across the country failing to meet expectations.
“We were hopeful for rain in September and October, but unfortunately, most areas, including central Anatolia, Marmara, Aegean, Mediterranean and some western Black Sea regions, saw little to no precipitation. Only the eastern Black Sea region recorded significant rainfall,” Özdemir explained.
He warned of escalating risk as reservoir levels continue to drop. “With Istanbul’s reservoirs hovering around 20% and some below that threshold, the danger is serious and growing. When reservoir capacity falls below 10%, the water becomes increasingly unusable due to sediment and bottom-layer water, complicating treatment and driving costs higher.”
Looking ahead, Özdemir stressed that precipitation in December and January, especially snowfall, is critical for replenishing water reserves. “If these rains and snows do not materialize, Istanbul and the wider region face serious water shortages.”
He also highlighted the importance of water conservation measures that extend beyond reducing household consumption. “Energy consumption must also be managed carefully because a significant portion of Türkiye’s electricity comes from hydroelectric plants, which depend on reservoir levels.”
On agricultural practices, he urged a shift from traditional flood irrigation methods to drip irrigation, which is far more water-efficient. “Current irrigation systems waste vast amounts of freshwater that must be conserved,” Özdemir said.
Recently, Istanbul has experienced a major issue with water discoloration and unpleasant odors, raising serious concerns about water management in the city. The Republican People’s Party (CHP)-led Istanbul Metropolitan Municipality (IBB), responsible for overseeing ISKI and water services, has been criticized for missteps in handling these problems.
