Effect of Tidal Events on Water Quality of Sungai Perai Penang, Malaysia

The increasing demand for water in developing countries, driven by economic growth and rising living standards, has led to significant environmental challenges, including the degradation of river water quality. This study was carried out to study the effects of tidal events on the water quality of Sungai Perai Penang, Malaysia. Eight sampling sites were selected for the analysis of some water quality parameters during the neap and spring tides of January, February, April and May 2024. Conductivity (EC), Total dissolved solids (TDS), Salinity (Sal), Dissolved oxygen (DO), Temperature (Temp) and Transparency (TRPC) were measured in situ. Biochemical oxygen demand (BOD), Total suspended solids (TSS), Phosphate (PO4), Nitrite (NO2), Ammonia (NH3), and Chlorophyll-a (Chlrp a) were analysed in the lab using standard methods. The results showed that water quality parameters varied with the following ranges: EC (0.12- 413 µS/cm), TDS (73.23-98,466 mg/l), Sal (0.05 48.87 ppt), pH (6.4 to 7.8), DO (1.83-10.74 mg/l), BOD(0.24-7.14 mg/l), TSS (0.01-0.43 mg/l), PO4 (0.27-4.41 mg/l), TRPC (0.03-183 m). NO2 (63.83-109.6 μg/l), NH3 (0.5-0.74 mg/l), Temp (28.9-31.27oC), and Chlrp-a (0.26-6.89 μg/l). EC, TDS, Sal, pH, BOD, TSS, PO4, TRPC, and Chlrp a were higher during spring tide which could be due to increased tidal range and stronger currents causing greater mixing and movement of water. ANOVA results showed that TDS, Salinity, Temperature, and Chlorophyll-a showed significant spatial variation (p<0.05), while the other parameters did not vary spatially (p>0.05). EC, TSS, PO4, NO2, NH3, pH, TDS, TRPC, and Sal showed significant variation between spring and neap tides (T-test, p<0.05). Spring tides are found to have a more pronounced effect on water quality compared to neap tides. This study highlights the combined influence of tidal events, anthropogenic activities, and diurnal cycles on the river's water quality. Understanding these dynamics is crucial for developing effective monitoring and management strategies to mitigate the impacts of pollution and ensure the sustainability of water resources in tidal rivers.