Geographia Technica, Vol 21, Issue 2, 2026, pp. 51-69
COMPARATIVE ASSESSMENT OF WATER QUALITY AND TROPHIC LEVEL INDICES IN SUMBERKIMA COASTAL WATERS, BULELENG, PROVINCE OF BALI, INDONESIA
Iis TRIYULIANTI, Eghbert Elvan AMPOU, Dessy BERLIANTY 
, Yoke Hany RESTIANGSIH, Vivi Eka INDRAYANI
ABSTRACT: The assessment of water quality in this study utilized the Water Quality Index (WQI) and Trophic State Indexes (TSI and TRIX) values as crucial components of information required for managing aquatic resources. The primary aim of this study was to compare the evaluation of water quality in the coastal waters of Sumberkima, Buleleng, Province of Bali, using the performance of WQI, TSI, and TRIX values. The WQI, TSI, and TRIX values were derived from measurements of dissolved oxygen (DO), nutrient levels, and chlorophyll-a (ChA), pH, temperature, salinity, and turbidity. Water samples were collected from the surface waters at 37 physical stations and 18 chemical and biological stations. The WQI ranged from 80.00 to 96.60 with mean value was 89.44 ± 3.66 revealed the water quality was good to excellent. The TSI and TRIX values for assessing trophic level in marine coastal waters of Sumberkima ranged from 12.76 – 65.13 with mean value was 30.73 ± 13.96 (TSI) and (4.41 ± 0.69) for TRIX values across all monitoring stations. The comparative indices of trophic level revealed that the coastal waters of Sumberkima were categorized as oligotrophic, mesotrophic, and eutrophic according to TSI values, while TRIX had four (4) classes of trophic level. Furthermore, TRIX values showed a stronger correlation with WQI (R2= 0.3418) than TSI (R² = 0.006). The findings of this study suggest that the TRIX value possesses a more comprehensive and strong trophic classification to characterize water quality. This study addresses a critical research gap in the identification of trophic levels by integrating physical, chemical, and biological assessments of water quality parameters.
Keywords: Water quality index (WQI); Trophic state index (TSI); Trophic index (TRIX); Sumberkima coastal waters; Spatial analysis.
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