Hydrological Assessment for Watershed Health in a Headwater Sub-Basin of the Rio Grande de Arecibo, Puerto Rico

The Río Grande de Arecibo (RGA) Watershed is a crucial source of water for the residents of the Island of Puerto Rico, including those living in the San Juan metropolitan area that are supplied by the North Coast Super Aqueduct. It is also significant for forest conservation, with five state forests providing around 10% of the watershed’s protected forest area. However, land cover changes in the region are putting the watershed’s sustainability at risk, as is the case in many places worldwide. This study takes an integrated socioecological approach to examine environmental changes in a headwater sub-basin of the RGA Watershed over a 20-year period (2001-2021). Using the Soil and Water Assessment Tool (SWAT), we assessed the impact of land cover changes on water sustainability. Our findings indicated that the headwater sub-basin of the RGA showed a decrease in both Forest Land and Range Land and an increase in Urban Built-up Land cover 20 years later. The results from SWAT provided the information to establish a “less healthy” condition 20 years later, due to the increase in the surface runoff metric and a decrease in the lateral flow metric. The study provides a baseline for future socioecological watershed studies and sustainable management actions, and its novel approach, combining geospatial analysis with hydrological modeling, could be applied to other watersheds, particularly in the tropics, where such studies are scarce.