HR: 16:45h
AN: H54C-03    [Abstracts]
TI: Importance of Dry-Season Precipitation to the Water Resources of Monteverde, Costa Rica
AU: * Guswa, A J
EM: aguswa@email.smith.edu
AF: Picker Engineering Program, Smith College, Northampton, MA 01063 United States
AU: Rhodes, A L
EM: arhodes@email.smith.edu
AF: Department of Geology, Smith College, Northampton, MA 01063 United States
AB: 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. Changes in regional land-cover and global climate may lead to reduced precipitation and cloud cover and a subsequent decline in endemic species, and a boom in ecotourism has put stress on water resources. A recent attempt to withdraw water from a local stream led to a standoff between conservationists and business developers, and there is a clear need for hydrologic data and understanding in support of policy. Through signals observed in the stable isotopic composition of precipitation and streamflow, we seek to understand how precipitation from the drier seasons propagates through the hydrologic cycle. In precipitation, δ¹⁸O and δ²H are heaviest during the dry and transitional seasons and light during the rainy season, consistent with the condensation mechanisms and degree of rainout typical of these periods. The signal in d-excess indicates a contribution of recycled water to precipitation in Monteverde from late in the rainy season through the dry season. Attenuated versions of these seasonal signals propagate through to the stream samples and provide a means of determining the importance of dry-season precipitation to water resources for the region. Results from six catchments on the leeward slope indicate that the Brillante Gap in the continental divide exerts strong control on the input of orographic precipitation to the region. Disparities in the temporal signals of precipitation and streamflow isotopes indicate non-linear behavior in the hydrologic processes that move water through these catchments.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1840 Hydrometeorology
DE: 1860 Streamflow
DE: 1884 Water supply
SC: Hydrology [H]
MN: Fall Meeting 2005