Ayung River Study Rates Overall Water Quality as Poor (C)

Denpasar — A 2025 journal study found that the Ayung River in Bali was in the Poor (C) category overall after analysing water-quality data from 2020 to 2024 at seven monitoring stations. The authors identified BOD and COD as the main factors behind the river’s degraded water quality.

The study, Evaluasi Kualitas Air Sungai Ayung Metode WQI (Water Quality Index) Sebagai Dasar Penanganan Pencemaran dan Rekomendasi Pengelolaan Sungai, was published on 18 December 2025 in the Journal of Innovative and Creativity, according to the journal article page and PDF. The researchers used the Water Quality Index method and compared results with Class II water-quality standards.

The paper says it assessed pH, dissolved oxygen (DO), BOD, COD and total suspended solids (TSS) from secondary data collected over five years. It also says the river showed temporal variation across seasons and years, but no consistent long-term improvement trend.

According to the article, the upstream section of the river performed better than the middle and downstream sections, suggesting pollutant accumulation as water moved downstream. The authors said organic pollutants, especially BOD and COD, were the dominant contributors to water-quality decline.

The study also describes the Ayung as Bali’s longest river, with a length of about 69.36 kilometres and a watershed of around 300.84 square kilometres. It says the river supports raw-water supply, irrigation, tourism and aquatic ecosystems.

Key findings from the study

• Monitoring period: 2020–2024
• Monitoring stations: seven
• Parameters analysed: pH, DO, BOD, COD and TSS
• Overall status: Poor (C)
• Reference standard: Class II water quality

The paper recommends integrated management to reduce organic pollutant loads and to tailor measures to seasonal conditions and different river segments. It also links pressure on the watershed to domestic, agricultural and tourism activity in the basin.

A separate earlier study on the Ayung River published by Udayana University researchers in 2022 found the river’s upstream, middle and downstream segments were in the lightly polluted category based on different parameters and methods, showing that river-quality assessments have varied depending on the dataset and approach used.

Sources

• Journal of Innovative and Creativity
• Universitas Mahasaraswati / Udayana-related journal page