Interbasin river mapping between Californian and Turkish rivers for climate change assessment

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A climate change assessment for streamflow availability of the selected rivers in Turkey is presented. Using an Index Basin Mapping (IBM) approach, climate change information is transferred across hydrologically similar rivers. This approach maps rivers of interest without downscaled climate information to index rivers where climate projections are available. Then, monthly perturbation ratios of index rivers, conveying projected climatic changes, are applied to the mapped rivers. Climate change effects on monthly streamflow availability and timing in eight selected rivers are evaluated under 20 scenarios produced from 10 General Circulation Models (GCMs) under medium and high emission cases. Results show that winter streamflow availability will increase due to more precipitation falling as rainfall rather than snowfall. Spring and summer streamflow availability will decrease due to reduced snowmelt runoff. Monthly streamflow variability will increase in all evaluated rivers. Out of eight selected rivers, the Çoruh, Yeşilırmak and Zamantı Rivers will be the most affected by climatic changes, with 14.6, 4.1, and 5.6% reductions in overall water availability under the high emission ensemble scenario. Overall water availability is projected increase in the Ceyhan and Göksu Rivers with climate change. Increased monthly streamflow variability can complicate water management in the region.