Feedback of land subsidence on the movement and conjunctive use of water resources

Wednesday, 17 December 2014: 9:00 AM
Randall T Hanson, USGS California Water Science Center San Diego, San Diego, CA, United States, Wolfgang Schmid, CSIRO Land and Water, Canberra, ACT, Australia and Joseph Davis Hughes, USGS Florida Water Science Center Lutz, Lutz, FL, United States
The dependency of surface- or groundwater flows and aquifer hydraulic properties on dewatering-induced layer deformation is not available in the USGS’s groundwater model MODFLOW. A new integrated hydrologic model, MODFLOW-OWHM, formulates this dependency by coupling mesh deformation with aquifer transmissivity and storage and by linking land subsidence/uplift with deformation-dependent flows that also depend on aquifer head and other flow terms. In a test example, flows most affected were stream seepage and evapotranspiration from groundwater (ETgw). Deformation feedback also had an indirect effect on conjunctive surface- and groundwater use components: Changed stream seepage and streamflows influenced surface-water deliveries and returnflows. Changed ETgw impacted on irrigation demand, which jointly with altered surface-water supplies resulted in changed supplemental groundwater requirements and pumping and changed return runoff. This modeling feature will improve the impact assessment of dewatering-induced land subsidence/uplift (following irrigation pumping or coal-seam gas extraction) on surface receptors, inter-basin transfers, and surface-infrastructure integrity. A hypothetical example and the Central Valley are used to demonstrate the utility and importance of the new subsidence model linkages for conjunctive use.