UNDERSTANDING CONNECTIVITY OF MEANDERING STREAMS AND SHALLOW AQUIFERS: LESSONS LEARNED FROM AN OBSERVATIONAL STUDY IN NORTHERN NEW MEXICO

The bidirectional feedback between streams and aquifers changes over several spatio-temporal scales, requiring a complex, multi-variable observational network that captures the dominant processes taking place and the response to changes in hydrologic forcing. The importance of the stream-aquifer connectivity and its dynamic nature is evidenced by its influence in the hydrologic response and the fate and transport of solutes at the watershed scale. With this in mind, and to better understand the dynamics of these systems and the effects that intra-annual weather variability has on physical and chemical processes, a monitoring network was installed at a meander bend of the East Fork of the Jemez River in the Valles Caldera National Preserve (VCNP), a snow-dominated watershed in northern New Mexico. This work summarizes two years of observations of groundwater-surface water interaction. Spatio-temporal patterns of water level, temperature, and electrical conductivity were measured in meander-bend wells and vertical fluxes to/from the stream were estimated using in-stream piezometers, subsurface thermal records, and distributed temperature sensing in the channel. A three-dimensional numerical model is used to synthesize data and draw general conclusions. The observational network has been collecting data since the summer of 2010 to present, overlapping the Las Conchas fire in the VCNP (largest wildfire on record in New Mexico’s history), and therefore representing a valuable data set to evaluate the hydrological and biogeochemical implications of wildfire events.