Abstract

This study provides a holistic assessment of a Complex Water Basin (CWS) at a basin scale located in the northeastern region of S & atilde;o Paulo State. The basin has undergone significant land use and land cover (LULC) changes and fluctuating surface, groundwater demands, over the past few decades. A CWS is conceptualized as a group of interconnected water components that adapt collectively in response to endogenous and exogenous factors. In this study, these components are represented by hydroclimatic, LULC, and water governance data. The assessment combines spatial and temporal analysis from 1982 to 2020, integrating hydrological and statistical methods, remote sensing and in situ monitoring data, as well as information on water management decisions, to track CWS changes and reconstruct its timeline. Due to the distinct spatial and historical LULC transitions and climatic conditions, hydrological responses to climate and LULC changes are discernible. Water governance was established in the nineties during the onset of these changes. Historically, climate change events affected the basin regionally, associated with increasing temperatures and decreasing rainfall; while LULC change events mostly affected downstream sub-basins that transitioned to agricultural use. Additionally, the frequency of drought periods has increased in recent years, which can interfere with the recharge of the sandy, unconfined aquifer. However, traditional water management faces challenges in integrating water demand and LULC changes. A holistic understanding of CWS can help reveal the status of the water resources and evaluate pathways toward water resilience.