Baseflow and water resilience variability in two water management units in southeastern Brazil

Changes in climate and water demand in densely populated regions increasingly affect hydrological systems, and, in turn, impact socioeconomic conditions. In this case study, we identify how the hydrogeological frameworks of two water resource management units, Tietê-Jacaré (TJ) and Piracicaba-Capivari-Jundiaí (PCJ) in Sao Paulo state (Brazil), control the baseflow processes and resilience in the face of streamflow fluctuations in response to anthropogenic activities and climate variation. The results reveal between 40% and 75% contributions of baseflow to total streamflow in basins overlying crystalline and sedimentary aquifers. The basins in PCJ which mostly overly crystalline aquifers, have shorter water residence times and greater dependence on surface water. Therefore, streamflow in the PCJ basins is vulnerable during the drought period and the management model affected the water resilience of the basins (transfer of water to Cantareira System). The TJ basins have greater streamflow contributions from aquifer discharge linked to the presence of important sedimentary aquifers, which improves resilience under changing rainfall patterns, these basins present a more stable situation of resilience. Ultimately, the two management units require different planning strategies with adaptive and dynamic actions to mitigate the social, economic, and environmental effects caused by the variability and reduction of water sources

Stable isotopes reveal groundwater to river connectivity in a mesoscale subtropical watershed

The Corumbataí River basin (São Paulo, Brazil) has a critical situation regarding water availability due to the intensive use to support agriculture and urbanization, requiring scientific information to face water demand. The aim of this study is to present a hydrological characterization based on the analysis of seasonal isotope variations (rainfall, groundwater, and surface water) and hydrometric data. Results indicate that baseflow contribution varies from 50 % to 70 % of the total flow, and water isotopic composition denotes a seasonal regime marked by the mixing of surface and groundwater in the wet period and groundwater discharge during the dry season. The results presented indicated the strong seasonal connection between atmospheric inputs and water movement across the basin, which poses an urgent need to diversify monitoring methods and create feasible regional and political regulations to control the effects on basin water resilience in the face of climate change and growing demand.La cuenca del río Corumbataí (São Paulo, Brasil) tiene una situación crítica en cuanto a la disponibilidad de agua debido al uso intensivo para apoyar la agricultura y la urbanización, requiriendo información científica para hacer frente a la demanda de agua. El objetivo de este estudio es presentar una caracterización hidrológica basada en el análisis de variaciones isotópicas estacionales (precipitaciones, aguas subterráneas y superficiales) y datos hidrométricos. Los resultados indican que la contribución del caudal base varía del 50% al 70% del caudal total, y la composición isotópica del agua denota un régimen estacional marcado por la mezcla de aguas superficiales y subterráneas en el período húmedo y la descarga de aguas subterráneas durante la estación seca. Los resultados presentados indicaron la fuerte conexión estacional entre los aportes atmosféricos y el movimiento del agua a través de la cuenca, lo que plantea una necesidad urgente de diversificar los métodos de monitoreo y crear regulaciones regionales y políticas viables para controlar los efectos sobre la resiliencia del agua de la cuenca frente al cambio climático y el crecimiento. demanda.Universidad Nacional, Costa Rica.Universidad Estatal de Sao Paulo, Brasil.Escuela de Químic