İSKİ Announces Completion of Istanbul Water Tunnel Project

The Istanbul Water and Sewerage Administration (İSKİ) confirmed that the Kağıthane–Bahçelievler–Sefaköy drinking‑water tunnel has been fully constructed and received its first water. The 20,630‑metre long, 4,000 mm diameter tunnel draws water from the Melen Basin, treats it at the Kağıthane Water Treatment Plant, and transports it to the European side of Istanbul. Tests of pressure, leak‑tightness and disinfection were completed before the inaugural flow.

The tunnel provides a daily transmission capacity of 1.5 million cubic metres, supplying the Eyüpsultan, Bahçelievler and Sefaköy reservoirs and strengthening the city’s main water‑distribution system against supply risks. The project was financed entirely from İSKİ’s own resources and is presented as a strategic infrastructure investment for Istanbul’s long‑term water security.