Assessment of Water Quality Data Using Functional Data Analysis for Klang River Basin, Malaysia

Rivers are subject to different sources of pollution. Continuous monitoring of river water quality provides an important basis for the authorities to take appropriate action. Water quality monitoring stations located within the river basin can provide necessary water quality data to establish any changes observed in the river water quality. It is important to highlight lower water quality status at specific monitoring stations so that immediate action can be taken. Similarly, it is an utmost important to ensure water quality at monitoring stations close to water catchment areas always at an acceptable level. This study aims to identify such monitoring stations using descriptive and functional data analysis. The approaches were applied to water quality data collected by the Department of Environment Malaysia at 16 stations in the Klang River basin from January 2013 to December 2016. Specifically, the functional boxplot was applied to identify the monitoring station with outlying properties. We identified many occasions when water quality deteriorated or improved largely due to the increase of COD, BOD and TSS. In addition, three stations close to two main catchment areas and forest reserve showed consistently good water quality. These indicate that the surrounding areas of the stations at the upstream of the rivers are still protected from uncontrolled pollution sources. The study is critical for the authority to understand the overall pattern of water quality data at each station so that action can be planned locally to preserve good river water quality.