The complexity of vadose zone, groundwater and surface water interactions presents hydrological research challenges specifically in the area of quantifying groundwater recharge. To acknowledge unity of the surface and groundwater systems requires an interdisciplinary approach that organizes knowledge about an analysis domain based on hydrologic units rather than on aquifers, enabling an integrative, system viewpoint of the terrestrial hydrologic system. By establishing the relationship between landscape components and water balance characteristics, hydrologic response units are established. This dissertation hypothesizes that regionalization can identify hierarchical hydrogeological units (HHUs) composed of unique combinations of surface water, groundwater and vadose zone landscape characteristics with statistically different recharge rates (p<0.05), and that these units can be used to estimate the renewable water flux of the groundwater system. Three interdependent studies were pursued to address the hypothesis:
(i)a statewide regionalization of mean annual streamflow that defined independent hydrologic regimes within Minnesota;
(ii) a regionalization focusing on East Central Minnesota which established unique HHUs based on unique combinations of landscape characteristics with statistically significant differences in mean minimum recharge;
(iii) a water management application which used the regionalization methodology to quantify the renewable groundwater flux and assess a water resources sustainability indicator within the Twin Cities Metropolitan Area.
Results from the three studies indicate that landscape characteristics control the rate of renewable water flux within the groundwater system. The results identified at one analysis scale could be used to extrapolate data at refined scales where long-term hydrologic monitoring data is lacking but informed water management decisions are crucial for the sustainable future of freshwater resources. Within the state of Minnesota, five hydrologic regimes were identified, each with varying inter- and intra-annual flow characteristics. Kendall-tau results suggest that mean annual streamflow within the regimes is either increasing or remaining stable. Focusing on a smaller, regional analysis territory within East-Central Minnesota, regionalization using the Watershed Characteristics Approach (WCA) identified HHUs composed of unique combinations of hydrogeologic characteristics, bedrock material, Quaternary thickness, topography and available water capacity. These HHUs and their corresponding minimum monthly recharge rates represent the renewable groundwater flux. HHUs previously identified within the Twin Cities Metropolitan Area (TCMA) were used together with water use estimates to calculate the sustainability indicator for each community within the TCMA. Although the WCA has few assumptions, limitations of the methodology include that the hierarchical refinement is based on the availability of streamflow data, and the accuracy of the estimated recharge rates associated with each HHU is pre-determined by the resolution of spatial landscape attribute data. Future research should further evaluate the defined HHUs to confirm that they are consistent for all five of the hydrologic regimes identified within Minnesota.