Publication Date

4-9-2007

Abstract

The forests of Monteverde, Costa Rica are renowned for their biological diversity and the many rare and endemic species that inhabit them. Originally protected for water supply, these forests attract ecologists and tourists to the small community on the leeward slope of the Cordillera de Tilaran. While economically beneficial, the growth associated with the rise of ecotourism has strained water resources. Water for supply is taken directly from streams and springs in these forests with little or no storage, and stream chemistry is significantly affected by the direct discharge of graywater. The community is strongly dependent on precipitation for both water supply and to ensure adequate dilution of its wastewater. Climate in this mountainous region is controlled by the migration of the Intertropical Convergence Zone, and the steep topography leads to significant spatial variability in precipitation inputs. The rainy season, May through October, is characterized by intense convective events that deliver to Monteverde an average of 2000 mm of rain during these six months. For the remainder of the year, the trade winds increase in strength and carry moisture up from the Caribbean Sea. This orographic uplift keeps the highland forests immersed in clouds and fog, and average rainfall is approximately 600 mm during these drier months. While the dominant input of water occurs during the rainy season, our stable isotope analyses indicate that orographic precipitation maintains stream baseflow during critical periods of the drier season. Combined with recent climate modeling work that predicts an increase in cloud-base height and a concomitant decrease in dry-season precipitation, this indicates a susceptibility of the water resources of Monteverde to a changing climate.

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