The Rise of Istanbul’s Shrinking Reservoirs

As Istanbul’s water reserves quickly evaporate, everyone needs to be on board to tackle the impending crisis.

Istanbul is running out of water. A “Day Zero” scenario once feared in Cape Town and São Paulo is drawing nearer. Unless the city acts decisively, the taps of this ancient metropolis could soon dry. 

On 16 September 2025, Istanbul’s reservoirs were only at 34.27% capacity, according to data released by İSKİ and reported in Cumhuriyet. Out of the ten reservoirs that supply water to 16 million inhabitants, at least one was reported to be below 10%. Water bodies that once appeared to be vast lakes now resemble semi-arid plains. The former Izmir-Çeşme highway, long submerged due to the construction of the Alaçatı Kutlu Aktaş Dam, can now be crossed by foot.  

These figures, obtained from the city’s water authority, reflect a worsening trend that has developed over over decades. For the biggest city in Europe, they serve as a clear warning signal of systemic vulnerability and an impending water crisis. 

Climate fingerprints

The obvious culprits are reduced rainfall and prolonged drought periods caused by climate change. Indeed, the rainfall record demonstrates the climate-induced volatility that climate change brings. Annual rainfall patterns show a declining trend: between 2015 and 2018, catchment areas typically had figures of about 350 mm. This decline was sharply contrasted in 2021 when the country experienced catastrophic flooding, killing almost 100 people. “This is the worst flood disaster I have seen,” Interior Minister Suleyman Soylu told reporters at the time. 

Despite the record-breaking deluges, the reservoirs failed to recover. Decades of urban expansion, drained wetlands, and damaged catchment areas meant that Istanbul’s reservoirs were only slightly above 50% capacity in 2021, according to data from the İSKİ. It is a trend that has persisted for over a decade and remains largely unaddressed. Comparisons over time highlight the scale of deterioration. On 16 September 2015, reservoirs were above 60% capacity; by 16 September 2025, they had fallen to just a third.  

A two-week downward slide 

When we zoom in, even short-term numbers tell the same story. Between 3 September and 16 September 2025, reservoir capacity fell 5% from roughly 39% to 34%, according to İSKİ’s daily monitoring. This steady slide reflects a sustained demand that the system cannot sustainably meet. 

Much of Istanbul’s water stress is self-inflicted. Per-capita consumption remains far above the European average, driven by unchecked urban growth, luxury housing complexes with artificial lakes, and inefficient irrigation in peri-urban farms. Meanwhile, industries discharge wastewater without adequate recycling. This relentless overuse depletes reservoirs faster than rainfall can replenish them, making shortfalls a structural, not seasonal, problem.  

The cost of complacency

The policy response to this decade-long crisis has been to build more dams and pipelines, importing water from increasingly distant sources. Yet the September 2025 figures, demonstrate the futility of a supply-only approach. Furthermore, mega-projects such as the construction of Istanbul International Airport opened in 2018, and the proposed Kanal Istanbul, an artificial shipping channel that will bypass the Bosporus, threaten crucial watersheds, compounding the problem rather than solving it. 

As İlhan Akgün has argued in her article on İklim Masası, scarcity is only one dimension of Türkiye’s water crisis. Pollution and a disrupted water cycle are equally dangerous, though often overlooked. Roughly one-fifth of Türkiye’s wastewater is treated only at the most basic level, and less than half undergoes advanced treatment. This means that even when water is physically available, it is often too polluted to use, a reality that came into sharp focus during the 2021 Marmara “sea snot” disaster. 

Agriculture adds further pressure, consuming more than three-quarters of Türkiye’s freshwater while contaminating it with fertilizers, pesticides, and saline runoff. The lesson for the City on Seven Hills is clear: unless scarcity, pollution, and climate change are tackled together, reservoirs will not be enough to secure the city’s future. 

Toward resilience

Having outlined the issues, now let’s talk about the solutions. Instead of betting on rainfall or building new dams, Istanbul needs a systemic strategy for resilience. Protecting watersheds and restoring wetlands is essential, but equally urgent is reducing inefficiencies: nearly 20% of the city’s water is still lost through leaks, the equivalent of an entire reservoir wasted. 

Comprehensive research by The Istanbul Planning Agency stresses that solutions must go beyond supply. Its 2023 report calls for mandatory water-saving fixtures in homes, widespread greywater reuse, leak-proof irrigation in agriculture, and the industrial use of treated wastewater. It also warns that mega-projects like Kanal Istanbul will devastate basins already under pressure. 

Citizen’s role

Citizens also matter. Simple actions, repairing leaks, using efficient appliances, watering gardens at night to prevent evaporation, collecting rainwater, add up. These crucial behaviour changes have, in part, been influenced by public outreach. During past droughts, İSKİ’s awareness campaigns showed measurable drops in household consumption.  

Recent national initiatives underscore the importance of this civic responsibility. As Esra Karataş Alpay reports in TRT World, Türkiye’s National Water Efficiency Initiative, launched on World Water Day 2025 under the motto “Water is Homeland, Protect Water, Protect the Homeland,” has used high-profile displays, public trainings, and digital campaigns to highlight conservation as both an environmental and national duty. In Istanbul alone, nearly 36,000 citizens participated in water literacy training sessions in 2024, while public monuments like the Galata Tower and the Bosphorus bridges were illuminated to project water-saving messages. 

These efforts have been crucial in informing citizens about how they can help mitigate the water crisis while ensuring everyone takes responsibility in working towards water resilience. 

A warning, not just a number

The figure 34.27% reported on 16 September 2025 may be the last trickle before levels hit rock bottom. It serves as a stark reminder that Istanbul is approaching a potentially-catastrophic water crisis. Sustainable solutions – such as restoring natural watersheds, upgrading infrastructure, and implementing integrated water policies – driven by awareness-building campaigns are essential to ensure the city’s resilience for future generations. 

Istanbul’s history has always been tied to water, from Byzantine cisterns to Ottoman aqueducts. Today, in the era of climate crisis, water scarcity is once again shaping the city, this time as a threat. The lesson could not be clearer: the reservoirs are running dry, and so is the time to act.