Water Resources Research Act Program

Details for Project ID 2017MT313B

Exploring Hydrologic Connectivity Between Shallow and Deep Groundwater Flow Systems in Upland Catchments

Institute: Montana
Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-10-01
Total Federal Funds: $20,520 Total Non-Federal Funds: $41,497

Principal Investigators: Payton Gardner

Abstract: The partitioning of water between surface, soil and groundwater reservoirs, determines the volume of storage and the rate of transmission of water through a watershed. Surface water and shallow soil water reservoirs have lower storage volumes and faster response times than groundwater reservoirs, and the partitioning of water between these reservoirs will exert primary control on watershed response to weather and climate. Little is known about the connection of soil flow and deep bedrock groundwater systems in mountainous areas where these interaction are complicated by high slope angles and complex topography and geology. In this project, the primary goal will be to investigate the interaction between shallow soil flow and deep bedrock groundwater in upland catchments, and to determine the dominant physical processes controlling their interaction in space and time. In order to physically measure hydrologic connection of soil and deep groundwater systems, we will drill and complete nine coupled shallow soil (<2 m) and deep groundwater (> 10 m) well nests on an upland hill slope in the Lubrecht Experimental Forest, Northwest of Missoula. These wells will be drilled across a variety of landforms including convergent and divergent zones. Soil moisture, saturated water level, soil temperature and conductivity probes will be installed in soil wells. Water level, temperature and conductivity transducers will be installed in groundwater wells. These physical parameters will then be collected continuously over the fall and winter of 2017 and spring and summer of 2018. We will augment physical hydraulic measurements with chemical and isotopic samples of soil and deep groundwater wells. We will then compare the relative timing and magnitude of soil water saturation and deep groundwater water table response. Correlation and magnitude of hydraulic response provides a first order measure of the hydrologic connectivity between the soil and deep groundwater at each location. Chemical and isotopic signals will be used to constrain fluid fluxes, water age and provenance. Relationships between the degree of connection and landscape position, bedrock and soil material properties will be explored using full Richards equation numerical modeling of hillslope flow and transport. The final products will include: 1) the workflow and technological expertise for drilling deep groundwater wells on rugged, remote hillslopes 2) the establishment of a long-term hydrologic monitoring location and a seed dataset for increasingly complex investigation and interpretation of soil water-deep groundwater connection and 3) an outdoor laboratory to bring students and classes to learn about hillslope hydrology, streamflow generation and groundwater recharge. This project will allow two young faculty members to develop expertise in an area of need in the hydrologic community, provide a seed data set from which write future large proposals to answer fundamental questions in watershed and groundwater hydrology, advancing hydrology and hydrologic education in Montana and throughout the world.