Selection of spatial scale for assessing impacts of groundwater-based water supply on freshwater resources. (1st September 2015)

• Record Type: Journal Article
• Authors: Hybel, A.-M.; Godskesen, B.; Rygaard, M.
• Is Part Of: Journal of environmental management. Volume 160(2015)
• Page Start: 90
• Page End: 97
• Publication Date: 2015-09-01
• Subjects: Groundwater abstraction -- Water supply -- Water withdrawal impacts -- Water stress -- Water footprint; EU-WFD European Union Water Framework Directive -- EWR environmental water requirements -- LCA lifecycle assessment -- RBMP River Basin Management Plan -- WR annually available water resource -- WS Water supply -- WSI Water Stress Index -- WTA Withdrawal-To-Availability ratio -- WU annual freshwater withdrawal; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2015.06.016
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Indicators of the impact on freshwater resources are becoming increasingly important in the evaluation of urban water systems. To reveal the importance of spatial resolution, we investigated how the choice of catchment scale influenced the freshwater impact assessment. Two different indicators were used in this study: the Withdrawal-To-Availability ratio ( WTA ) and the Water Stress Index ( WSI ). Results were calculated for three groundwater based Danish urban water supplies (Esbjerg, Aarhus, and Copenhagen). The assessment was carried out at three spatial levels: (1) the groundwater body level, (2) the river basin level, and (3) the regional level. The assessments showed that Copenhagen's water supply had the highest impact on the freshwater resource per cubic meter of water abstracted, with a WSI of 1.75 at Level 1. The WSI values were 1.64 for Aarhus's and 0.81 for Esbjerg's water supply. Spatial resolution was identified as a major factor determining the outcome of the impact assessment. For the three case studies, WTA and WSI were 27%–583% higher at Level 1 than impacts calculated for the regional scale. The results highlight that freshwater impact assessments based on regional data, rather than sub-river basin data, may dramatically underestimate the actual impact on the water resource. Furthermore, this study discusses the strengths and shortcomings of the applied indicator approaches. A sensitivity analysis demonstrates that although WSI has the highest environmental relevance, it also has the highest uncertainty, as it requires estimations of non-measurable environmental water requirements. Hence, the development of a methodology to obtain more site-specific and relevant estimations of environmental water requirements should be prioritized. Finally, the demarcation of the groundwater resource in aquifers remains a challenge for establishing a consistent method for benchmarking freshwater impacts caused by groundwater abstraction. Graphical abstract: Highlights: The freshwater withdrawal impact on a sub-river basin scale is assessed. Spatial resolution is increased from regional to groundwater body scale. Increased spatial resolution markedly changes the quantified freshwater impact. Regional scale impact assessment does not reveal local water stress. Uncertain environmental water requirements influence results.