The Quebrada Negra wetland study: An approach to understand plant diversity, hydrology, and hydrogeology of high-Andean wetlands

Abstract

High-Andean peatlands are high-altitude wetland ecosystems found throughout the arid central Andes of South America. They form through the establishment of specialized grasses and cushion sedges that are well-adapted to cold temperatures, in areas where groundwater emerges. The Silala River is a groundwater-fed high-Andean fluvial system, which emerges in various springs that generate wetlands, the Cajones and Orientales (Bolivia), the river’s headwater sources, and the Quebrada Negra (Chile) being the most important. This article reviews detailed monitoring undertaken in the undisturbed Quebrada Negra wetland to provide insights into wetland processes, and to compare its functioning to that of the Bolivian wetlands, which were channelized a century ago. Vegetation composition was found to be similar among the three wetlands, and their spatiotemporal vegetation cover distribution showed strong seasonal and interannual variability. The channelized Bolivian wetlands have the highest annual actual evapotranspiration values (similar to 700 mm, due to their higher vegetation vigor), as estimated using remote sensing, similar to 10% greater than that obtained in the undisturbed Quebrada Negra wetland. For the Quebrada Negra wetland, groundwater monitoring revealed that hydraulic head contours are consistent with the topography, although water sources to the wetland are complex to identify. While significant groundwater inflows arise at the wetland edges, upwelling and downwelling conditions are observed at various locations within the wetland, similar to other high-Andean wetlands. The observations suggest that while the underlying groundwater discharge sustains the saturated conditions of the wetland, the spatial variability of groundwater inputs results in a negligible impact of channelization on wetland evapotranspiration. This article is categorized under:nWater and Life > Stresses and Pressures on EcosystemsnScience of Water > Hydrological Processes