THE IMPACT OF HUMAN ALTERED GEOMORPHOLOGY ON THE SEASONAL DISTRIBUTION PATTERN OF WATER PHYSICOCHEMICAL AND NUTRIENT PARAMETERS IN THE TERENGGANU RIVER ESTUARY, MALAYSIA

Abstract

River estuaries are under intense pressure and tremendous changes due to development. Such changes will affect water quality and circulation and add pressure on the aquatic environment. In this study, we determine the seasonal distribution pattern of water physicochemical and nutrient parameters in the Terengganu River estuary after significant geomorphological changes. Our results show dissolved inorganic nitrogen had the highest values during fall inter-monsoon (19.61 ± 8.61 μmol N/L). Heavy rainfall during the northeast monsoon reduced the water temperature (25.5 ± 0.68°C), improved dissolved oxygen level (5.9 ± 0.5 mg/L), lowered pH values (5.6 ± 0.5), increased suspended particulate matter (71.9 ± 24.2 mg/L) and turned the estuary into a freshwater system. Extreme dry weather during spring inter-monsoon (2016) resulted in the incoming tide pushing coastal seawater inwards, reaching stations located 10.24 km (S1-Nerus River) and 9.43 km (S4-Terengganu River) away and turned the water column slightly saline (1.4 – 2.92 psu). In comparison to year 1999-2000, saltwater was only detected 5.27 km from the estuary mouth. These data are crucial for future estuarine dynamic modelling to improve development planning and coordination of upstream water discharge at Kenyir dam and downstream water extraction for human consumption