Year: 2026 | Month: January | Volume: 13 | Issue: 1 | Pages: 323-330
DOI: https://doi.org/10.52403/ijrr.20260131
Water Quality Index of The Kusan River Watershed Using The IKA-INA (Modified Indonesian Water Quality Index) Method in Tanah Bumbu Regency
Firman Hadinata1, Syarifuddin Kadir2, Muhammad Syahdan3, Fatmawati4
1Natural Resources and Environmental Management Study Program, Lambung Mangkurat University
2Forestry Study Program, Lambung Mangkurat University
3Marine Science Study Program, Lambung Mangkurat University
4Aquaculture Study Program, Lambung Mangkurat University
Corresponding Author: Firman Hadinata
ABSTRACT
The Kusan River Watershed (DAS) is one of three major watersheds in Tanah Bumbu Regency. Quoted from the ‘2024 Tanah Bumbu Regency Environmental Quality Monitoring Report’, the water quality of the Kusan River shows moderate pollution at the middle point and mild pollution at the upstream and downstream points. Indications of a decline in water quality due to industrial, mining, agricultural and domestic waste disposal have become a significant environmental problem in this region. This study focuses on the application of the IKA-INA method to analyse water quality in the Kusan watershed, with the aim of providing a comprehensive overview of the water conditions in the river. Water samples were collected at 11 surface water points in the Kusan River Watershed. The number of monitoring points was selected based on the spatial representation of water bodies in accordance with Minister of Environment and Forestry Regulation No. 27 of 2021, which emphasises the selection of points based on the function of water bodies, potential pollutants, and the purpose of water quality monitoring. The WQI Kusan Watershed values show spatial variation between river segments. The highest WQI was recorded in the downstream Kusan Watershed (77.63), while the lowest was in the Mangkal Api Hilir River (66.39). Sub- watersheds such as the Pendamaran River show an increase from upstream to downstream, while the Bakarangan River is relatively stable. The WQI Kusan Watershed in 2025 in stage II or the final stage is classified as good because the index range is 70 ≤ i ≤ 90 with an WQI of 73.51.
Keywords: Water Quality Index, IKA-INA Method, Kusan River Watershed
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