The impacts of climate change on water availability, a case study in Tietê river basin, Brazil.

The main purpose of this study is to discuss how assessing climate change impacts on water availability can drive new adaption links between three types of water uses: irrigation, urban and industrial water supply, and energy generation. This is a case study for the Tietê watershed, Brazil´s most populated region. The study quantified how water availability in the Tietê river basin behaves under two climate change scenarios (SSP-RCP 2-4.5 e 3-7.0), in two-time horizons - 2030 and 2050 - using the outputs of four Global Circulation Models (MRI-EMS2, MIROC6, GFDL and NOREMS2). All model data were bias-corrected, and the flow catchment was measured by a distributed hydrologic model, carried out by the Hydrologic Engineering Center-Hydrologic Modelling System (HEC-HMS). For energy generation the operation plants were simulated using the hydropower optimizer model, seeking to assess the impact on hydroelectric generation. Combined results suggest that the total mean yearly amount of water intend to increase in 2030 and 2050 (11-8% under 2-4.5 scenario and 16-14% under 3-7.0 scenario), but this water is concentrated in the rain season (up to 26% in February and 27% in March and April combined). All climate models also point to rate increases by 93% in peak flows. Climate change’s expected impacts indicate an enhancement in energy fluctuation, an increase in the product in spilled flows, and a higher risk of damage to nearby infrastructure, crop fields, and cities placed along the river. It is important to strengthen the synergy between users to guide responsible institutions to prioritize coordination, participation, and collaboration at the local level.