Water Resources Sustainability Indicator: Application of the Watershed Characteristics Approach

The quantification of the renewable flux (i.e. sustainable limit) of the hydrologic system is the prerequisite for transitioning from unsustainable to sustainable water resources management. The application of the Watershed Characteristics Approach to estimate the renewable flux of the hydrologic system was demonstrated using Minnesota's (USA) Twin Cities Metropolitan Area (TCMA). The methodology quantified the relationships between landscape properties and water balance characteristics, resulting in the development of functioning hierarchical hydrogeological units with corresponding recharge rates. This renewable flux is a key quantitative characteristic for the assessment of a sustainability indicator. The key indicator of sustainable water use is the ratio of the renewable capacity of the hydrologic system to the water use by humans and the environment. By incorporating water use estimates for the TCMA relative to the calculated recharge rates, sustainability indicators for groundwater and total flux were calculated for the metropolitan area. As far back as the 1890s, declines in TCMA groundwater levels have been observed, which correspond to the unsustainable groundwater extraction estimates identified in the results of this study. The non-stationary characteristics of urban watersheds influenced by ongoing land use/land cover changes as illustrated in this paper, emphasizes the need for conservative hydrologic planning to achieve sustainable water management. This approach can also be applied to other metropolitan areas as a hydrologic tool for decision-makers to design sustainable water policy and prevent the over-extraction of the water flowing through the hydrologic system.