Conservation Policy Changes in Protected Areas on Hilltops in Brazil: Effects on Hydrological Response in a Small Watershed

Public policies affecting land use/land cover also have an impact on water resource availability, and hilltop protected areas are a relevant factor in ensuring continued availability of water resources. The legislation ruling the delimitation of protected areas on hilltops has changed at the Brazilian national level in 2012 and in Rio de Janeiro state in 2014. However, these environmental legislation changes did not take into account the feedback effects of restricting protected areas to hilltops on the regularity of hydrological responses in watersheds. As such, this manuscript sought to analyze the contribution of hilltop-only protected areas to continued water availability. We analyzed hydrological responses in the São João river watershed, which provides water for domestic, industrial, and agricultural uses in the Região dos Lagos municipalities of Rio de Janeiro state. Our results show that designating only hilltops as protected areas, as prescribed under the new pieces of legislation, does not prevent abrupt changes in hydrological responses that can lead to changes in streamflow volume and regularity as well as increases in sediment flows, which may compromise drainage systems and continued water supply due to reservoir silting. Therefore, we conclude that protecting hilltops only, as established under current Brazilian legislation, is not sufficient to safeguard the environmental function of maintaining water resource availability.