Effect of the big flood events on the water quality of the Muar River, Malaysia

Abstract

This study is carried out in order to examine the impacts of flood events on water quality status of Muar River. The water samples consisting of six water quality parameters, namely dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, ammoniacal-nitrogen, pH value, and total suspended solids were used to compute the water quality index (WQI) at Muar River. Mean annually and monthly water quality variations of the nine sampling stations along Muar River over 2 years period (2006–2007) were investigated together with the monthly and annual rainfall pattern of the 22 rainfall stations within the basin. The relationship between monthly rainfall and water quality of Muar River for the period before and after the flood events was analyzed using Pearson correlation coefficient. In December 2006 and January 2007, the total monthly rainfall recorded was over 145 and 70 %, respectively, of the total monthly average rainfall of 31 years (from 1980 to 2010). The 2006/2007 Malaysian big flood events in December 2006 and January 2007 have resulted in lowest monthly WQI of 56.4 in Polluted category and within Class III in January 2007; while December 2006 and February 2007 flood events were categorized as Slightly Polluted and placed in Class III. Rainfall had higher correlation strengths with WQI and water quality parameters in the period before and during the first wave of flood events. Results of this study could be useful in supporting management decisions in mitigating the adverse effects of flood on the surface water resources.