WATER STORAGE DYNAMICS IN HIGH ELEVATION SEMI-ARID CATCHMENTS

Catchments are complex systems that evolve as a result of the interaction between climate, biota and landscape over long periods of time. Water storage capacity is a particular catchment descriptor that can provide insight on the evolution of catchments and their hydrologic and biogeochemical processes. In the snow-dominated catchments draining Redondo Peak (3432m) within the Valles Caldera National Preserve, New Mexico, precipitation seeps through highly permeable volcanic soils. In this area, perennial streams are sustained by subsurface water contributions as overland flow is almost negligible. As part of the University of Arizona Critical Zone Observatory four small catchments (<3.5 Km²) with similar bedrock and physical characteristics, but with main differences in aspect were instrumented for the determination of water fluxes and water chemistry. The main objective of this research is to understand the role of aspect on the temporal and spatial variability of storage dynamics in high elevation snow-dominated catchments. Data collected during the last four water years were analyzed using various methodologies: a water balance, a streamflow recession analysis, and tritium analysis of springs and streams. A daily water balance provides estimates of total storage changes. The recession analysis defines the characteristics of storage of the draining streams and a mean residence time is estimated with tritium measurements in springs and the catchment’s outlets. During the last four water years, annual precipitation ranged from 500mm to 680 mm. The water year 2008-2009 was the wettest and 2010-2011 the driest. Annual runoff ratios in the catchments (discharge/precipitation) varied between 0.07 to 0.25 showing northern facing catchments the higher values.