Water Quality Dynamics and Water Pollutions of Belawan Estuary, North Sumatra, Indonesia

The Belawan Estuary is a highly strategic area in Medan, North Sumatra Province. Various utilisation activities such as ports, transportation, industry, fisheries, tourism, and settlements in the Belawan Estuary area have resulted in ecological pressures, particularly water pollution. The aim of this study was to determine the water quality dynamics and pollution status of the Belawan Estuary. The study was conducted in October 2023 in the Belawan Estuary, Medan City, North Sumatra Province. The sampling points consisted of eight locations representing the mouth, middle, and outer parts of the estuary. Sampling was conducted four times following the tidal cycle: full moon, last quarter, new moon, and first quarter. Water pollution status was determined using the pollution index (PI), Malaysian Marine Water Quality Index (MMWQI), and Canadian Council of Ministers of the Environment (CCME) methods. Temperature and pH were the most stable quality parameters. Total dissolved solids (TDS) and salinity fluctuated both spatially and temporally. Spatially and temporally, the Belawan Estuary falls into the moderately to heavily polluted category. The sources of pollution in the Belawan Estuary are urban activities, primarily the Terjun landfill. Nutrients and coliform bacteria are the main water quality parameters contributing to Belawan estuary pollution.