SGER: How Do Hillslope-to Catchment-Scale Flowpaths Develop in Response to an Extreme Drought Followed by Record Precipitation

University Of Arizona, Tucson AZ

Investigators

Abstract

This study will take advantage of an unprecedented level of variability in precipitation in northern New Mexico to improve the mechanistic understanding of the routing and residence time of water within catchments. Northern New Mexico has been experiencing a severe drought for the last six years. The beginning of the 2006 water year continued this dry period with the lowest snowpack in recorded history resulting in first, second, and some third order streams at our study site running dry by summer 2006. The 2006 monsoon season however was characterized by the highest precipitation totals in 112 years which has reestablished flow in the formerly dry streams through the fall of 2006. We propose to take advantage of this unusual event, combined with ongoing studies in the ecohydrology of our study sites, to develop both the data and the model representations of the distributed hydrological response to variability in precipitation. Our study design includes eight nested first order sub-catchments located radially around a central mountain. These eight sub-catchments drain into three previously-instrumented streams, which subsequently join to form a single outlet from our study site. Although vegetation and parent material are similar throughout the catchments, variability in water and energy related to aspect result in very different patterns in soil depth and development. Initial stream geochemical monitoring, conducted as part of previous research efforts, suggests very different residence times of water related to these patterns in aspect. Our project will directly address the need for field data to actually test models of catchment flow path development, rather than simply match models. We expect this activity to make significant advances in understanding the controls on the spatial and temporal variation of water in the landscape. Furthermore, the physically-based, spatially-realistic representation of water movement at the hillslope to small catchment scale will allow a quantitative evaluation of how the production and export of biogeochemical cycling elements respond to variability in precipitation.