Studies find nutrient and pollution pressures in Tukad Badung River

Denpasar — Two recent scientific studies of the Tukad Badung in Denpasar have identified elevated levels of nutrients and organic pollution indicators at selected monitoring points, classifying sampled sections of the river as lightly polluted under Indonesia’s official water-quality framework.

The first study, published in the journal Presipitasi in March 2023, applied the national Pollution Index method to three sites representing upstream, midstream and downstream sections of the Tukad Badung within Denpasar City. The authors compared measured parameters with Indonesia’s Government Regulation No. 22 of 2021, which sets quality standards for river water used as a drinking water source.

According to the abstract in the Garuda research database and the journal article, average concentrations of total suspended solids (TSS), ammonia, biological oxygen demand (BOD) and chemical oxygen demand (COD) at these points exceeded the class I river-water standards in the regulation. Oil and grease and detergent concentrations remained within the applicable limits.

The Pollution Index used in the 2023 study is a composite measure that combines multiple parameters to indicate overall water quality status, rather than a direct reading of a single pollutant. Using this method, the three river monitoring points in Denpasar produced index values between 2.41 and 4.27, a range that the authors classified as lightly polluted under the Government Regulation No. 22/2021 categories.

What the 2025 nutrient study examined

A separate paper published in 2025 in Nature Environment and Pollution Technology focused on nitrogen and phosphorus dynamics and recovery potential along an 18‑kilometre stretch of the Tukad Badung. The study describes the river as an important water source increasingly affected by agricultural, domestic and industrial discharges.

The researchers carried out bi‑daily sampling — twice per day — at six strategically selected sites spanning upstream, midstream and downstream reaches. According to the paper, downstream locations consistently showed higher concentrations of nutrients and related pollutants than upstream sites.

Reported concentration ranges from the 2025 study included:

• Ammonia: 1.5–4.2 milligrams per litre
• Nitrate: 5.0–11.6 milligrams per litre
• Total phosphorus: 0.5–2.5 milligrams per litre
• Total suspended solids: 80–127 milligrams per litre

The authors note that afternoon measurements were generally higher than morning readings, which they associate with reduced river flow and increased anthropogenic inputs later in the day. Total suspended solids were highest at midstream sites, a pattern they link to localised sedimentation from human activities along the river corridor.

Beyond field measurements, the 2025 paper also tested nutrient recovery technologies in the laboratory. Precipitation and adsorption methods were reported to recover up to 80 percent of extractable nutrients from water samples, suggesting that contaminants such as nitrogen and phosphorus could potentially be reclaimed as a resource, reducing reliance on synthetic fertilisers.

The study describes the Tukad Badung as approximately 30 kilometres long but notes that the field campaign covered only an 18‑kilometre segment. Results from six sampling sites therefore illustrate conditions in that monitored reach and cannot be assumed to represent every tributary, discharge point or section of the wider watershed.

Interpreting the indicators and standards

Taken together, the 2023 and 2025 publications point to pressures on Tukad Badung water quality from domestic, agricultural and industrial activity, reflected in elevated TSS, ammonia, BOD, COD and nutrient concentrations at selected sites. However, the studies are designed as targeted monitoring and method demonstrations, not as a real‑time or island‑wide assessment of Bali’s rivers.

The pollution‑index findings show that the three Denpasar locations examined in 2023 fell into the lightly polluted category under national standards, based on exceedances of several key parameters. The nutrient‑dynamics study, using a different design and indicator set, mapped spatial and temporal patterns at six sites and explored the feasibility of nutrient recovery technologies.

For residents, planners and watershed managers, the evidence from these papers supports a focused conclusion: certain monitored sections of the Tukad Badung have exhibited elevated levels of nutrients, suspended solids and organic pollution indicators relative to Indonesia’s river‑water quality standards. Establishing current conditions across the whole river system would require regular, publicly documented sampling at more locations and integration with official environmental monitoring programmes.

Sources

• Garuda Kemdiktisaintek entry for “Assessment of Surface Water Quality Status Using the Pollution Index Method in Tukad Badung River”
• Presipitasi Vol. 20 No. 1 (2023) issue page
• AGRIS database record for “Nutrient Dynamics and Recovery Potential in the Tukad Badung River, Indonesia”
• Nature Environment and Pollution Technology – PDF of “Nutrient Dynamics and Recovery Potential in the Tukad Badung River, Indonesia”
• Eco-EET article citing Harmayani et al. (2023) Tukad Badung Pollution Index study