Thursday, April 28, 2016, 12:30PM - 1:30PM
SEEC room S225
For our last INSTAAR grad seminar of the semester, Adam Wlostowski will be presenting his work using the McMurdo Dry Valleys as the closest thing nature gets to a controlled experiment. Adam's findings elucidate the the dynamics of hyporheic water flow in these alien environments as well as typical watersheds closer to home. The talk will take place at 12:30 pm on Thursday (Apr 28) in SEEC S225. As usual, pizza lunch will be provided.
Hyporheic zone function in naked watersheds: Leveraging the unique context of glacial melt streams in the McMurdo Dry Valleys, Antarctica
The hyporheic zone is defined as the volume of mineral grains, water, and organic matter beneath and adjacent to stream channels where stream waters and groundwaters mix. Hyporheic waters are subjected to ecologically significant biogeochemical processes, such as nutrient transformations, thermal buffering, and chemical weathering. Streams in the McMurdo Dry Valleys (MDV) of Antarctica provide an unparalleled natural laboratory for studying hyporheic zones. Nearly all streamflow is generated by glacial melt, catchment hillslopes are hydrologically disconnected from stream channels, there is a complete absence of vascular vegetation, and continuous permafrost prohibits connectivity between streams and deep groundwaters. Leveraging the conceptual simplicity of the MDV hydrologic system, two complimentary studies will be presented to quantify transient hydrologic, chemical, and hydraulic dynamics of MDV hyporheic zones across disparate spatial and temporal scales. First, an end-member mixing approach is used to estimate hyporheic exchange fluxes on two streams, over 9 seasons of flow record. Model simulations reveal the 5-35% of total annual stream flow is exchanged through hyporheic zones and a greater portion of annual stream flow is exchanged through hyporheic zones on longer streams, relative to shorter streams. Further, model results help explain the chemostatic nature of silica observed MDV streams. Second, continuous water level data from a network of riparian wells are used to quantify the dynamic hydraulic response of hyporheic zones to the passage of daily melt water waves. Results reveal complex patterns of exchange between the stream channel and adjacent hyporheic aquifer. Results are used to interrogate common conceptual models of riverbank infiltration and ultimately elucidate how unsteady stream flow controls hyporheic exchange.