Ongoing energy development in the northern Green River structural basin necessitates information about groundwater resources that supply water to the basin’s wells. Many human activities in that area, including pumping water from the aquifers for agricultural, domestic, and industrial use, and penetration of the heterogeneous (that is, complex intertonguing of layers) aquifers (see Bartos and others, 2015) during deeper drilling for natural gas, have the potential to impact the aquifer system that supplies water to most wells in the area. We initiated this study in FY2012 as “A Retrospective Assessment of Groundwater Occurrence in the Normally Pressured Lance Formation and a Field Reconnaissance of Existing Water Wells in the Study Area.” The assessment was completed in 2012, but in 2013, ownership of the mineral rights to develop the Normally Pressure Lance Formation changed. Therefore, to assist agencies such as the BLM with upcoming development, the emphasis of the study was modified and previously collected data were used to develop a potentiometric-surface map (a visual representation of aquifer-water levels) for the lower Tertiary aquifer system that underlies the Green River Basin.
During 2010-2013, groundwater levels (depth to water and shut-in well-head pressure [the above-ground elevation to which groundwater would rise if released from a confined aquifer]) were measured according to USGS methods (Cunningham and Schalk, 2011) in 77 wells throughout the basin, including the proposed Normally Pressured Lance project area (Sweat, 2013). In 2014, depth to water was measured in 12 wells and shut-in water pressure was measured in 4 flowing wells. The 2014 water levels were used to augment the previously collected data for constructing a generalized potentiometric-surface map (a representation of groundwater-level altitudes in multiple hydrologically connected geologic units) of the Green River Basin lower Tertiary aquifer system.
The draft map indicates that groundwater in the study area generally moves from north to south, but this pattern of flow is altered locally by groundwater divides and by groundwater discharge to the Green River, Fontenelle Reservoir, and possibly to a tributary (Big Sandy River) and a reservoir (Big Sandy Reservoir). The final report and potentiometric-surface map will provide decision-makers with updated groundwater information and document groundwater levels for evaluating any future changes in the aquifer system. In combination with other WLCI monitoring activities, the groundwater-level data directly address the WLCI management objective to develop inventory and monitoring approaches for evaluating the overall effectiveness of WLCI habitat projects and supporting assessments of cumulative effects from changing land uses and other changes. These products also will support the BLM and other land and resource managers in their planning and decision-making for resource management in the WLCI region and beyond, and they will support future research.
Cunningham, W.L., and Schalk, C.W., comps., 2011, Groundwater technical procedures of the U.S. Geological Survey: U.S. Geological Survey Techniques and Methods 1-A1, 151 p., at http://pubs.usgs.gov/tm/1a1/.
Sweat, M.J., 2013, Groundwater well inventory and assessment in the area of the proposed Normally Pressured Lance natural gas development project, Green River Basin, Wyoming, 2012: U.S. Geological Survey Data Series 770, 27 p., at http://pubs.usgs.gov/ds/770/.
Products Completed in FY2014
- All water-level inventory data can be found at http://pubs.usgs.gov/ds/770/.
- Bartos, T.T., Hallberg, L.L., and Eddy-Miller, C.A., Hydrogeologic framework, groundwater levels, and generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system, 2010-14, in the northern Green River structural basin, Wyoming: U.S. Geological Survey Scientific Investigations Report (draft).
Products Completed in FY2013
- Preliminary data for all monitoring sites.
- Final data were published on USGS NWISWeb at http://waterdata.usgs.gov/wy/nwis/nwis.
- A preliminary potentiometric surface map was drafted using data collected in 2012 and 2013.
Products Completed in FY2012
- Sweat, M.J., 2013, Groundwater well availability for monitor network development in the proposed Normally Pressured Lance gas development project, Green River Basin, Wyo.: U.S. Geological Survey Data Series 770, at http://pubs.usgs.gov/ds/770/ .
- Presentations to the Bureau of Land Management, the Wyoming Department of Environmental Quality, and Encana USA.
