River water quality implication after the earthquake

Abstract

The earthquake of 6.0 Magnitude occurred in the Ranua district of Sabah lasted for 30 seconds on 5th June 2015. This study investigated the various water quality parameters such as turbidity, color, dissolved oxygen, pH, electric conductivity, total dissolved solids, and so on from two monitoring stations (Bambangan and Kimolohing). The secondary data was requested from the Water Department of Sabah, where the Liwagu river is the downstream system of Mesilau. Through the temporal trace of each parameter, the water quality parameters showed an abrupt change one day before the earthquake. Consequently, around two weeks after the quake, it reached its initial state rapidly. After the earthquake, the mean turbidity is 436.25 NTU with a standard deviation of 1416.86 NTU. Its peak was on 17th June with 5550 NTU, total dissolved solids were 58.68 mg/l, and the electrical conductivity was 122.98 μs/cm at the Bambangan station, while it was 673.00 NTU with a standard deviation of 1869.90 NTU and it peaked on 17th June with 3750 NTU in the Kimolohing. The dissolved oxygen hit the lowest level of 3.27 mg/l on 17th June when 4.19 mg/l. The nitrate concentration increased to the maximum of 0.18 mg/l and 0.15 mg/l in the Bambangan, and the Kimolohing station, respectively. The metal concentrations also increased after the earthquake at both stations. However, alkalinity and hardness had decreased since 30th April before the earthquake and continued to decline until 14th August, when it reached the initial level. The value of pH and chloride did not seem to be affected by the earthquake, as the concentration maintained the average level.