A multicriteria decision making framework integrating WEAP and MCDM for optimal water transfer from the Doogh River to the Gorganrud River in Iran

Inter‑basin water transfer (IBWT) is increasingly used to address water scarcity in arid and semi‑arid regions, yet these projects involve complex trade‑offs among economic, social, environmental and technical objectives. This study develops a comprehensive decision‑making framework for selecting the optimal discharge of a water transfer tunnel from the Doogh River to the Gorganrud River, upstream of the Bostan Dam in Golestan Province, Iran. A coupled simulation‑optimisation approach is employed, integrating the Water Evaluation and Planning (WEAP) model with three Multi‑Criteria Decision‑Making (MCDM) methods: AHP, TOPSIS and VIKOR. Six discharge scenarios (Q‑0.19, Q‑0.57, Q‑0.76, Q‑0.91, Q‑1.06 and Q‑2.00 m³/s) are evaluated against twelve criteria across four sustainability dimensions. The baseline scenario (without water transfer) reveals a substantial unmet water demand of 30.06 MCM/year, underscoring the need for the transfer. Results show that while the highest‑discharge scenario (Q‑2.00) performs best from a purely technical perspective, the intermediate scenario (Q‑0.91) provides an optimal balance, achieving 98% of environmental flow requirements with an estimated annual pumping cost of 0.417 billion Tomans (≈ 9,930 USD). This scenario exhibits strong robustness in sensitivity analyses under varying electricity prices and criteria weights. The proposed framework is transferable to similar water‑transfer projects in other arid regions.