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

2025-03-15T22:37:49+07:00

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.

Trend Analysis on Water Quality of Cimahi City’s Major Rivers

2025-03-26T05:49:02+07:00

Trends in water quality of three major Cimahi City rivers (Cibeureum, Cimahi, and Cisangkan) were evaluated using Mann–Kendall and Seasonal Mann–Kendall tests with Sen’s slope estimation for 12 parameters (TDS, TSS, BOD, COD, NO₂, NO₃, NH₃, T-P, Oil & Fat, Detergent, Fecal Coliform, Total Coliform) and two indices (Pollutant Index, PI and Indonesian Water Quality Index, WQI-INA) over 2017–2022. WQI-INA values remained in the “poor” to “very poor” categories for all rivers, with non-significant monotonic trends; only Cibeureum River exhibited a positive Sen’s slope of 2.22 units/year. Basic trend analysis revealed significant decreases in NH₃ concentrations across all sites (Sen’s slope range: –0.04 to –0.13 mg/L per season) and significant increases in NO₂ at all Cimahi River sites (0.005–0.017 mg/L per season). Seasonal trend tests identified four significant trends: decreasing PI at Cimahi downstream (z = –2.34), decreasing PI (z = –2.34) and T-P at Cibeureum midstream (z = –2.21), and decreasing COD at Cibeureum downstream (z = –2.01). Seasonal trend tests also found that dry-season improvements exceeded wet-season gains, indicating dominant groundwater baseflow dilution. Variability assessed via coefficient of variation highlighted the highest fluctuations in NH₃ (CV = 1.99), Fecal Coliform (CV = 1.92), and Total Coliform (CV = 1.53), versus lowest in TDS (CV = 0.47), NO? (CV = 0.75), and T-P (CV = 0.86). The variation also found that spatially, Cimahi upstream showed greatest variability, Cibeureum downstream the least. These patterns underscore active nitrification processes, laundry-effluent inputs, and seasonal hydrodynamics as key drivers. Enhanced monitoring frequency—particularly for microbiological and carbonaceous parameters—and refined seasonal sampling are recommended to improve trend detection and inform targeted management strategies.

Indonesian Journal of Limnology

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

Trend Analysis on Water Quality of Cimahi City’s Major Rivers