The Assessment of River Pollution on Linggi River Basin due to Sand Mining Activities

The Linggi River Basin has a catchment area of 1,300 km2. The river passes through Seremban town and several industrial estates before it was discharged into the Strait of Melaka. The main tributaries include Pedas River and Rembau River. A large portion of the basin has been converted from forest to agricultural, industrial, commercial and residential uses has the potential to negatively impact on water quality within Linggi River. The objectives of the study is to develop a standard effluent disposal for sand mining to enable the proclamation of the legislation and regulations by authorities. In order to meet these objectives, numerical models have been used to quantify the impact of sand mining activities on river water quality. Numerical models have been calibrated and validated to field measurements. Hydrologic and hydraulic modelling have been applied for assessing rainfall, runoff, and hydraulic conditions. Pollution load modelling have been used for assessing the generation of pollutants and the subsequent runoff water quality. Modelling of the sand washing effluents was undertaken solely with the AD module due to the nature of the sediment, which mainly consisted of fine sediment and where possible to observed TSS measurements. Exclusions were applied to modelling of other point and non-point sources of pollution along these rivers. An in-bank 1D (MIKE 11) hydraulic model of the main waterway in the study area has been developed extending to the Straits of Melaka so that important tidal impacts can be included in simulations. The hydraulic model has been calibrated against the available water level and discharge measurements for the period 1970-1990. A Manning’s resistance value of 30 (n=0.033) for the main channel was found to best reproduce water level records. The findings of this analysis indicate that water quality within the Linggi River Basin typically does not meet Class IIA or IIB standard. The Best (Environmental) Management Practices (BMPs) are possibly the most effective practical methods of reducing environmental impact levels and improving riverine water quality in Malaysia through the adoption of BMPs for sand-mining operations.