The application of environmental isotopes to conceptualize groundwater recharge in a coastal aquifer system: Case study of the West Coast Aquifer System, South Africa

摘要: Abstract Knowledge of natural recharge mechanisms the West Coast Aquifer is vital for implementation water resource management strategies, which would secure groundwater resources region. The analysis stable (2H and 18O) radioactive (3H 14C) environmental isotopes have been employed to identify source residence times shallow, confined bedrock aquifers based on sampling conducted during 2017 2018. δ18O values ranged from −4.34 0.65‰ while δ2H −18.8 6.8‰. Groundwater 3H activity 0.0 1.2 T.U, rainwater tritium was 1.4 T.U 14C contents 1.2pMC. isotope signatures revealed four groups: non-evaporative shallow deep with similar isotopic composition indicating same recharge; enriched signature show evaporation effect precipitation where clay lenses are locally absent; indicate recently infiltrated water; not recharged by surface when drought conditions persist. Deep in low-plain discharge zone seawater intrusion evidenced elevated chloride concentration (35700 mg/l) composition. High (>0.8 T.U) containing were found downgradient area, confirms recent active occurs a distance postulated area. Tritiated older ages had as younger consistent it being derived low altitudes. calculated carbon-14 suggest under different climatic cooler periods late Pleistocene Holocene (~2717–33000). radiocarbon age reflected aquifer supports localized system via focused mechanism. application methodology combined an understanding geology study area led development coherent conceptual flow model.