Development of an operational index of water quality (PoS) as a versatile tool to assist groundwater resources management and strategic planning

•An innovative index (PoS) for groundwater's quality assessment is introduced.•Characterization is based on the cumulative effect of 13 key quality parameters.•PoS index performs comparisons between samples of different reference conditions.•It provides an alternative tool for the identification of water quality driving factors.•PoS index may be used as a versatile tool for groundwater management and policy making.

SummaryGroundwater quality assessment and evaluation is of paramount importance in strategic planning and management at river basin scale or even larger. Depending on the available infrastructure data upon which such assessments are carried out, significant variations in terms of measured parameters and time span covered occur frequently and pose objective difficulties to environmental assessments. Still, there is a need for evaluation across such basins at regional, national or even continental scales under a common reference base. Existing methods so far focus on the comparative evaluation of a single parameter or a common set of parameters that needs to be available throughout all examined basins. Moreover, existing approaches and practices are assessing groundwater in comparison to the quality standards set for a specific use despite the fact that often these resources are covering a multitude of functions. This paper presents an index that attempts to perform a comparative assessment of groundwater quality across basins controlled by the same or different factors, subject to the same or different pressures and characterized by different availability of water quality measurements spread over the same or different time periods. It serves as an easy to implement and unbiased approach to identify water quality controlling factors. The proposed method offers on the spot assessment of groundwater quality characteristics visualized in a way that is easily conceived and comprehended.