Stable-isotope and solute-chemistry approaches to flow characterization in a forested tropical watershed, Luquillo Mountains, Puerto Rico

摘要: Abstract The prospect of changing climate has led to uncertainty about the resilience forested mountain watersheds in tropics. In where frequent, high rainfall provides ample runoff, we often lack understanding how system will respond under conditions decreased or drought. Factors that govern water supply, such as recharge rates and groundwater storage capacity, may be poorly quantified. This paper describes 8-year data sets stable isotope composition ( δ 2 H 18 O) precipitation (4 sites) a stream (1 site), four contemporaneous sample solute chemistry isotopes, used investigate watershed response inputs 1780-ha Rio Mameyes basin Luquillo Mountains northeastern Puerto Rico. Extreme O values from low-pressure storm systems deuterium excess d -excess) were useful tracers this tropical system. A hydrograph separation experiment performed June 2011 yielded different but complementary information data. results indicated 36% rain reached soil surface left very short time runoff. Weathering-derived solutes near-stream was displaced into at beginning event, followed by significant dilution. more biologically active exhibited net flushing behavior. d- analysis suggested streamflow typically recent component (∼25%) with transit less than sampling resolution 7 days, well-mixed (∼75%). showed an overall increase dissolved concentrations decreasing elevation related inputs, geology, slope position. considerable amount events runs off quickflow bypasses subsurface flowpaths, better shallow hillslope deeper processes require sub-weekly detailed modeling. combined isotopic approach can guide further studies comprehensive model hydrology, inform decisions for managing supply future changes land use.