Hydrologic data for the effects of forest cover on base flow of streams in the mountainous interior of Puerto Rico

The U.S Geological Survey, in cooperation with the Puerto Rico Department of Natural and Environmental Resources, completed a study to determine whether a relation exists between the extent of forest cover and the magnitude of base flow at two sets of paired drainage basins in the highlands of the municipalities of Adjuntas and Utuado within the mountainous interior of Puerto Rico. One set of paired basins includes the Ro Guanica and Ro Tanam, tributaries of the Ro Grande de Arecibo. The other set of paired basins includes two smaller basins in the drainage basin of the Ro Coabey, which is a tributary of the Ro Tanam. This paired set of small basins was used to verify if basin size is a determinant in the relation between forest cover and the magnitude of base flow. The paired basins in each set have similar rainfall patterns, and geologic substrates and aspect; the only difference is the extent of forest cover and related land uses such as the cultivation of shade coffee. Data on the, hydrology, hydrogeology, subsurface geology and the stable isotopes composition of hydrogen and oxygen in rainfall, vadose zone groundwater and streamflow were used in the analysis. The principal objective of the study was the comparison of base flow per unit area for basins with different areal extents of forest cover and related land uses such as shade coffee and sun coffee.

美国地质调查局（U.S Geological Survey）与波多黎各自然资源与环境部（Puerto Rico Department of Natural and Environmental Resources）合作完成一项研究，旨在探明波多黎各山区内陆阿胡托斯（Adjuntas）和乌图阿多（Utuado）自治市高地内两组配对流域的森林覆盖范围与基流（base flow）规模之间是否存在关联。第一组配对流域为阿雷西博大河（Ro Grande de Arecibo）的两条支流——瓜尼卡河（Ro Guanica）与塔纳姆河（Ro Tanam）。另一组配对流域则包含塔纳姆河支流科阿韦伊河（Ro Coabey）流域内的两个小型子流域，该组流域被用于验证流域面积是否为影响森林覆盖与基流规模关联的决定性因素。每组内的配对流域具有相似的降雨模式、地质基底与坡向，唯一差异仅为森林覆盖范围以及遮阴咖啡（shade coffee）种植等相关土地利用方式。本次分析采用了水文、水文地质、地下地质数据，以及降雨、包气带（vadose zone）地下水与河川径流中的氢、氧稳定同位素组成数据。本研究的核心目标为对比不同森林覆盖面积占比及遮阴咖啡、全日照咖啡（sun coffee）等相关土地利用类型的流域的单位面积基流规模。