Water-energy nexus: Integrating hydrochemical characterization and life cycle assessment for a holistic profile of agricultural groundwater sustainability

Sustainable groundwater management is critically hampered by a disconnect between water quality assessment and environmental impact (EI) of its extraction infrastructure, particularly at the micro-level. This study applied a novel micro-nexus lens to bridge this gap by developing a holistic sustainability profile for a single agricultural pumping well in Labu Kubong, Malaysia. The objectives were outlined as follows: (i) to characterize hydrochemical properties and evaluate groundwater suitability for paddy irrigation utilizing Piper, Gibbs, Wilcox, and United States Salinity Laboratory (USSL) diagrams; (ii) to pinpoint dominant environmental hotspots from raw materials and energy consumption using a cradle-to-gate Life Cycle Assessment (LCA); (iii) to validate LCA reliability with Monte Carlo uncertainty analysis; and (iv) to synthesize the hydrochemical and LCA results into a holistic sustainability balance sheet (HSBS). The Piper diagram results indicated calcium-magnesium-bicarbonate-type water, with rock weathering identified as the predominant geochemical process by the Gibbs diagram. The groundwater was classified as excellent for irrigation (C2-S1 class) by Wilcox and USSL diagrams. Counter-intuitively, LCA revealed that dominant EI originated not from operational energy consumption (1.65 %) but from the embodied footprint of the raw materials from groundwater extraction infrastructure. Raw material production, particularly polyethylene terephthalate (61.6 %), copper for the submersible pump (14.8 %), gravel packing (4.51 %), steel (3.5 %), copper wire for the electrical cable (2.05 %), polyvinyl chloride (1.12 %), and high-density polyethylene (0.0062 %), were the primary contributors. This integrated micro-nexus paradigm offers HSBS, highlighting a significant paradox whereby intrinsic groundwater suitability for paddy agriculture and unsuitability for drinking without treatment due to elevated concentrations of iron (1.71 mg/L), manganese (0.173 mg/L), and arsenic (0.04 mg/L) occur alongside significant extrinsic EI resulting from its extraction infrastructure. This HSBS provides policymakers a crucial tool for integrated management decisions, enabling balanced consideration of usability, operational risk, and life cycle impacts to support truly sustainable groundwater management.