Building resilience in the Global South: Evidence from a decentralized water policy in Brazil

Climate change poses increasing risks to population well-being through heightened water scarcity. This threat is particularly pronounced in low-income and climate-vulnerable regions, where traditional water infrastructure may not be feasible in the near term. This study evaluates the effectiveness of a decentralized water policy as a climate adaptation strategy, focusing on Brazil's Cisterns Program, a large-scale rainwater harvesting initiative designed to build climate resilience in remote, underserved communities. The analysis shows that access to rainwater harvesting reduces severe cases of waterborne diseases by approximately 34%. Beyond these average health gains, the study assesses climate resilience by examining how the program moderates the impacts of drought shocks. Using multiple definitions of drought, the analysis shows that these events substantially increase disease burden. However, these adverse effects are significantly mitigated or fully offset by the program, indicating a sharp reduction in vulnerability to climate-related stress. Evidence on mechanisms suggests that effectiveness depends not only on water availability but also on beneficiaries' capacity to manage water safely and on program implementation. Impacts are significantly larger in more educated communities and where local civil-society organizations play a central role in implementation. These findings highlight the potential of low-cost, decentralized interventions as viable climate adaptation strategies, particularly in settings where large-scale infrastructure projects are impractical, and offer a scalable model for resilience-building development policies in the Global South.