Do protected areas enhance surface water quality across the Brazilian Amazon?

Protected Areas (PAs) are pivotal instruments in natural resource conservation and maintaining or enhancing ecosystem services, including hydrological functions. In the Amazon, the impact of PAs on the quality of river waters remains largely overlooked. Therefore, this study aims to evaluate whether Environmental Protected Areas (EPAs) and Indigenous Lands (ILs) efficiently protect the quality of surface waters in the Brazilian Amazon. Water quality variables from river gauge stations distributed across the lowlands Amazon are analyzed according to baseline river hydrogeochemistry classification, both inside and outside PAs. This study found that whitewater and clearwater rivers coursing within EPAs and ILs show lower turbidity and electrical conductivity compared to those outside PAs, likely due to the buffering effect of dense forest cover within protected landscapes. Moreover, data indicate that protected areas enhance the water quality from upstream unprotected landscapes in the Brazilian Amazon. These results highlight the need to further invest on effective mechanisms of water resource conservation across lowland tropical regions, and particularly in the Earth's largest watershed.