A Framework for Assessing the Stability of Groundwater Quality Using Reliability and Resilience

Abstract

Groundwater protection from pollution involves several actions, and groundwater-quality evaluation is one of the basic and important steps that help in adequate planning and management of the groundwater resources. Of the several methods available for evaluating groundwater quality, water quality indices help to easily communicate scientific and technical knowledge to end users involved for taking appropriate actions to ascertain sustainable groundwater protection. Formulation of a water quality index follows four steps of selecting parameters, their transformations, assigning weights, and aggregation. However, it is found that the existing indices generally use the groundwater-quality dataset recorded through a monitoring network at a chosen point of time, and hence, none of the indices account for the temporal variability of groundwater quality. The proposed framework uses RRV statistical indicators of reliability (Ry), resilience (Re), and vulnerability (Vy) and aggregates the two indicators, i.e. reliability and resilience, to develop a novel index of groundwater-quality stability. The RRV criterion has been earlier utilized in the performance assessment of water resources systems, drought management, and assessment of watershed health. However, unlike the earlier studies, the multiplicative form of only Ry and Re indicators is found efficient in evaluating groundwater-quality stability. The RRV-based stability index is superior to other indices because the former amalgamates the temporal variability with deviations of groundwater quality from the standards prescribed by the World Health Organization (WHO). Use of the RRV stability index avoids use of other measures for capturing the temporal variability or the dynamics of groundwater quality such as coefficient of variation. The stability index can be satisfactorily applied to a multi-year or a multi-season database of groundwater quality. It is worth mentioning that computation of the stability index does not require assigning arbitrary weights to different quality parameters, and hence, the index is free from subjectivity or bias. The stability index is a useful, preferable, excellent indicator of the groundwater-quality stability and has the potential to prove its applicability in different aquifer systems of the world. The stability index may be integrated with the modern tools and techniques such as the geographic information system and the geostatistical modeling to depict spatial distribution of the groundwater-quality stability over an area. Usability of the index may be proved under different hydrogeologic settings in future studies for better planning and management of water resources so that problems arising due to polluted aquifer systems and degraded groundwater quality could be avoided.