Transboundary water allocation and environmental flows (Ural River basin case study)

This study focuses on developing scientifically grounded approaches to transboundary flow allocation in the Ural River Basin, considering ecosystem needs and international approaches to aquatic ecosystem conservation. Amid increasing competition for water resources and climate change, there is a growing necessity to shift from allocating fixed water volumes toward more flexible, ecosystem-oriented solutions. Based on an analysis of international practices, the provisions of the existing agreement on the joint use and protection of water bodies in the Ural River Basin, and an assessment of the current state of its aquatic ecosystems, the study highlights the need to revise established water allocation mechanisms. Methods. The research is based on analyzing international approaches to transboundary flow allocation, statistical processing of reconstructed hydrological observation series, and a comprehensive assessment of aquatic ecosystems using abiotic and biotic indicators. It also applies methods of critical hydrological conditions and ecohydrological normalization for calculating environmental flow. Results. The study proposes an approach to justify environmental flow as a key element in the system of transboundary water resource allocation. Based on an assessment of ecosystem conditions in the Ural River Basin, the objectives for implementing environmental flow have been formulated, including reserving a portion of the flow to maintain and restore ecosystems, adapt to climate change, and preserve biodiversity. Estimated environmental flow volumes near the Russia–Kazakhstan border have been identified, which may serve as a basis for planning joint decisions on water resource allocation that take ecosystem needs into account. The results can be applied by intergovernmental commissions and expert groups in refining transboundary water allocation mechanisms.