Assessment of Ground water Quality and Seawater Intrusion Potential in the Klang River Basin, Malaysia Using Hydro-chemical Analysis and MODFLOW Simulation

The study assessed the groundwater quality and seawater intrusion possibility based on the long-term hydro-chemical monitoring data and the numerical groundwater flow models. Klang River Basin in Malaysia was assessed choosing monitoring well S9 with regards to groundwater under the historical records (1998-2018) and physical parameter; pH, temperature, electrical conductivity (EC), total dissolved solids (TDS) and chemical parameters (major ions and selected trace metals). The electrical conductivity (EC=193.66 gS/cm) and the TDS (range: 270-600 mg/L) are indicative that the groundwater is mostly fresh. The chloride levels were between 68 and 100 mg/L, which is much lower than the seawater intrusion level of 250 mg/L, indicating that there was not much impact of the sea. The trace metals of arsenic (-0.0046 mg/L) and mercury (-0.00035 mg/L) were systematically less than EPA guideline values but iron concentration levels remained high (mean 9.45mg/L), probably because of geogenic sources or borehole material. The MODFLOW model assumed a confined to unconfined aquifer system with constant-head boundary conditions along the coastal margin, no-flow boundaries from mean annual rainfall (2,420 mm/yr), Hydraulic conductivity and storage coefficient were derived from JMG pumping test records. A three-dimensional Visual MODFLOW model with data on pumping tests indicated that the drawdown (<0.01 m) of well S9 was negligible currently. The outcomes suggestedequilibrium ground water situations with minimal seawater intrusion potential whereas revealing the necessity to monitor the iron concentration and ground water extraction at the most urbanised basin.