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.