Indonesian Journal of Limnology

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

Ahmad Muhtadi — 2025-04-27

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

Adam Rus Nugroho — 2025-04-29

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.

Domestic Wastewater Influent Treatment in Reservoir B of Lampung University Using Constructed Wetlands (CWs)

Elhamida Rezkia Amien — 2025-05-02

This study aims to analyze the effectiveness of the Constructed Wetlands (CWs) method in improving the quality of domestic wastewater before it enters Resevoir (Embung) B at Universitas Lampung. Embung B, which has the largest storage capacity on campus, also receives domestic wastewater (grey water) from residential areas and a terminal. The CWs method was applied using bamboo water (Equisetum hyemale) and water jasmine (Echinodorus palaefolius), with and without the addition of moss. Water quality parameters such as pH, TSS, BOD, COD, NH?-N, TDS, EC, temperature, and DO were tested. The results show that the combination of bamboo water with moss (P3) and water jasmine with moss (P4) was the most effective in reducing pollutant concentrations, with several parameters such as TSS, pH, and NH?-N meeting the domestic wastewater quality standards in accordance with Government Regulation No. 22 of 2021. Although BOD and COD did not fully meet the standards, there was a significant reduction compared to initial conditions. These findings suggest that the CWs system has potential as an eco-friendly and cost-effective technology for domestic wastewater treatment, especially in small-scale environments such as campuses or residential areas.

Comparison of Interpolation Methods for Mapping Water Quality in Seloromo Reservoir

Rofiana Budi Ayumi Sita Dewi — 2025-08-01

Spatial interpolation is GIS modeling to estimate the value of an unmeasured location point based on measurements at another location. However, research on choosing the best interpolation method for a sample to become a continuous map is still limited. The main objective of this study is to compare three interpolation methods to show the spatial distribution map of water quality in Seloromo Reservoir, Pati Regency. Water quality measurements in terms of pH, EC, and TDS parameters consist of 50 sample points for each parameter. Water sampling was conducted in February 2023 from morning to afternoon. The three interpolation methods include inverse distance weighting (IDW), Gaussian kriging (GK), and spline. The results show that each interpolation method used will result in different interpolation maps. The best interpolation method in this study is inverse distance weighting (IDW). The IDW method has the best R-Square (pH 0.824; EC 0.85; TDS 0.873) and RMSE (pH 0.146; EC 0.93; TDS 0.563) values compared to the other two methods. This research is limited to comparing the results of mapping water quality distribution.

Assessing Coastal Soil Capacity and Flood Risk in Kulon Progo Coastal Area, Indonesia

Ikrom Mustofa — 2025-08-21

The coastal areas of Kulon Progo, including the salt marshes, play a vital role in mitigating hydrometeorological disasters by regulating water flow. However, rapid land-use changes driven by the construction of Yogyakarta International Airport (YIA) have altered the region’s environmental balance. This study investigates the water retention capacity of coastal soils in Kulon Progo and examines how differences across land-use types may influence flood risks. Rather than tracking changes over time, the study uses cross-sectional comparisons and historical land-use and flood data to infer potential impacts of land transformation on hydrological hazards. Field investigations using standard soil physical property analysis were conducted at nine sites across three villages (Jangkaran, Palihan, and Glagah) in Kulon Progo to capture variations in soil characteristics related to land use changes from the airport development and its buffer zones. Bulk density ranges from 1.16 g/cm³ to 2.18 g/cm³, particle density between 2.46 g/cm³ and 5.15 g/cm³, and porosity levels from 48.16% to 66.67%. Areas near converted lands show higher density and lower porosity, reducing infiltration and increasing surface runoff. Historical flood data from the Regional Disaster Management Agency (BPBD) indicates rising flood frequency over the past decade, especially after major land conversions. This trend aligns with the study’s findings, as areas with lower porosity experience recurrent flooding. The reduced absorption capacity due to increased soil compaction is a key factor driving flood risks. This research supports Indonesia’s Nationally Determined Contributions (NDC) roadmap for climate adaptation by providing empirical evidence for disaster risk reduction. The findings highlight the need to preserve salt marshes and integrate soil management into land-use planning to enhance climate resilience and mitigate future flood risks in the Kulon Progo coastal region.