Importance of orographic precipitation to the water resources of Monteverde, Costa Rica

Monteverde, Costa Rica harbors montane forests that exemplify the delicate balances among climate, hydrology, habitat, and development. Most of the annual precipitation to this region arrives during the wet season, but the importance of orographic precipitation during the dry and transitional seasons should not be underestimated. Development associated with ecotourism has put significant stress on water resources, and recent work has shown evidence that changes in regional land-cover and global climate may lead to reduced precipitation and cloud cover and a subsequent decline in endemic species.Precipitation samples collected from 2003 to 2005 reveal a seasonal signal in stable isotope composition, as measured by δ18O and δ2H, that is heaviest during the dry and transitional seasons. Attenuated versions of this signal propagate through to stream samples and provide a means of determining the importance of precipitation delivered by the trade winds during the dry and transitional seasons to water resources for the region. Results from six catchments on the leeward slope indicate that topography exerts a strong control on the importance of orographic precipitation to stream baseflow. The contributions are greatest in those catchments that are close to the Brillante Gap in the Continental Divide. Differences in the temporal variation of precipitation and streamflow isotope compositions provide insight to the hydrologic pathways that move water to the streams.