气候变化领域集成服务门户

Increased sediment loading to reservoirs and, ultimately, to Guanica Bay and reef areas is a significant concern in Puerto Rico. Sediment deposition has significantly reduced storage capacity of reservoirs, and sediment-attached contaminants can stress corals and negatively impact reef health. In this study, we examined sediment yield from an upper mountainous watershed, Yahuecas, contributing sediment to Lago Yahuecas reservoir and eventually Guanica Bay, Puerto Rico, to gain a better understanding on sediment loss. This watershed was chosen because it was the only watershed where runoff was monitored in Guanica Bay basin. The Soil and Water Assessment Tool was calibrated and validated using 4 1/2 years of flow data (07/1980 to 01/1985) from the Yahuecas watershed. Five and a half years of suspended sediment concentration data (04/2000 to 09/2005) from the adjacent Adjuntas watershed were used to calibrate sediment simulation of the model because no sediment data were available for Yahuecas. After calibration and validation, Soil and Water Assessment Tool was used to evaluate temporal-spatial soil erosion and sediment yield and assess factors that impact sediment yield. From 1975 to 2011, approximately 80% of annual sediment yield occurred during the two rainy seasons (February to May and August to November). Heavy rainfall, erodible soils, and steep mountain slopes were the primary causes of sediment yield in the Yahuecas watershed. Land use that reduces the protective forest canopy (like sun-grown coffee farming) can exacerbate soil loss. More sediment per hectare was lost from areas producing coffee than forested or grass-covered areas. Conversion of coffee farming practices from sungrown to shade-grown will reduce soil erosion and sediment yield.