Temporal Variability of Water Quality Parameters: Surface and Groundwater Contamination

Temporal variability of water quality parameters provides essential information about surface and groundwater contamination dynamics. Seasonal and event-based fluctuations, driven by both natural and anthropogenic processes, are found consistent by long-term monitoring of various regions. Statistical analyses in groundwater (PCA, PCA-MLR, clustering) indicate high variability of parameters such as nitrate (NO₃⁻), total dissolved solids (TDS), electrical conductivity (EC), hardness and heavy metals Fe and Mg due to seasonal recharge, water–rock interaction, dilution during wet months, and introduction of agricultural fertilizer and domestic or industrial wastewater. Redox-sensitive constituents such as arsenic have quantifiable seasonal variations associated with water-table processes, pumping and recharge cycles. Surface water quality follows similar patterns: dilution of parameters such as EC and nutrients by wet-season dilution, and concentration of solutes and increases in biochemical oxygen demand (BOD), nitrogen (total N), and phosphorus (TP) during dry seasons. Multivariate analysis commonly indicates common sources of contamination—e.g., municipal sewage, agriculture, industrial effluent—with spatial distribution related to urban or agricultural land use. In controlled systems, like aquifer storage and recovery (ASR), temporal variability of treated surface water stored underground affects disinfection byproduct (DBP) formation. Groundwater-influenced zones generally exhibit lower organic loading and DBPs, but seasonal quality fluctuations and storage period increase these risks.