Simulation of the time of return of water supply shortages as an indicator of water resources governance in the PCJ basins

Código

I-EBHE0181

Autores

Sarah Dantas Rothéia Carvalho, José Anderson do Nascimento Batista, Evelyn Cristiane Valladares, CINTIA ELENA NICOLAU

Tema

WG 2.6: Water systems analysis for integrated planning & management

Resumo

Climate change emerges as one of the primary global challenges of the century, causing significant alterations in precipitation patterns and extreme weather. These changes have a direct impact on hydrology by transforming stationary time of return scenarios into non-stationary ones. Consequently, there is an evident need to develop water governance indicators that assess the performance of water systems under climate change. In this context, the PCJ basins (Piracicaba, Capivari, and Jundiaí) constitute a strategically important and potentially vulnerable region in terms of water availability and development for the Brazilian states of São Paulo and Minas Gerais. This study focuses on developing a methodology to evaluate the time of return of water supply shortages in the current hydrological infrastructure of the PCJ basins as a governance indicator, and on analyzing the evolution of this indicator in the study area. To achieve this, climate projections were obtained monthly over 11 sub-basins within the PCJ basins, from 2052 to 2081, following the planned implementation deadline for planned infrastructure. These projections were developed using the global climate model MIROC5 and the regional model Eta, under the RCP 4.5 climate scenario (moderate global greenhouse gas emissions), by the Brazilian Climate Projections Platform provided by the Brazilian National Institute for Space Research (INPE) and corrected using the 1977-2006 isohyets from the current Brazilian Geological Survey. Residuals of annual total precipitation were extracted and analyzed for their temporal trends across the sub-basins, adopting them as the random component of the hydrological system defining times of return. To assess the effect of precipitation on water availability, a monthly stochastic hydrological model and an annual regression of total precipitation with seven-day minimum natural flows were developed. The monthly model calibration was based on the 7Q10 streamflows of the study sub-basins, determined by regionalization. Finally, based on assumed constant water demands derived from data from the São Paulo State Department of Water and Energy (DAEE) and existing infrastructure, the time of return of water supply shortages was calculated for each sub-basin, representing the recurrence necessary for streamflow not to exceed demand. The standard deviation of precipitation residuals exhibited homoscedastic behavior, ensuring the validity of the statistical analyses of residuals. Climate projections indicated trends of annual precipitation reduction, resulting in significant decreases in 7Q10 and natural flows. Consequently, significant reductions in the time of return of water supply shortages were observed for all sub-basins over the analyzed period. It is concluded that, in such moderate climate change scenario, decreased time of returns.