<p>The estimation of programmable water amounts under climate change conditions is currently one of the essential tenets of sustainable water management. Several factors that need to be considered for improved accuracy affect the calculation of renewable surface water and groundwater. These factors include taking into account the return flow from consumptive uses, reservoir capacities within a planning horizon, expert opinions, groundwater storage capacity in alluvial aquifers and formations, and population growth projections. Multiple stations are used for climate change assessment to minimize uncertainty, and an ensemble averaging method and various scenarios are employed to reduce uncertainty in the availability of calculated renewable water. In this study, the computation of future renewable water was carried out while considering these factors, focusing on the mid-future timeframe (2040–2060). The LARS-WG 6 downscaling model was used to analyze climate change. According to the ensemble averaging model results for the basin, the monthly mean minimum temperature will rise by about 2.2 degrees Celsius on average, and the mean maximum temperature will rise by about 4.2 degrees Celsius on average. Next, the volume of renewable water resources is determined by water balance computations. The maximum sustainable surface water retention capacity for the year 2050 was calculated by taking into account the capacities of existing and under-construction reservoirs, including planned reduction coefficients. The study examined the distribution of renewable water resources among future water demands using six bankruptcy methods. Various uncertainty scenarios from 0.5 to 1.1 were also considered. Six social choice and fallback bargaining were used to evaluate the acceptability of solutions from different perspectives of water stakeholders. The allocation based on the CEA bankruptcy method was found to be the most favorable approach, except for the unanimity bargaining method.</p>