Council on Energy, Environment and Water Integrated | International | Independent
The new government in Delhi has embarked on an ambitious plan to transform the Yamuna into a vibrant tourist hub while restoring its ecological health. Reviving the river is also a welcome move for residents who have long endured its deteriorating water quality. The right to clean drinking water and sanitation is enshrined in Article 21 of the Indian Constitution, yet these services remain out of reach for many due to infrastructure gaps and governance challenges, faced particularly by urban local bodies and their parastatal agencies. One key issue is India’s inadequate used water treatment capacity. According to the Central Pollution Control Board (CPCB), only 44 per cent of municipal used water was treated in 2021, leaving more than half of such waste water generated in our cities and towns to flow untreated into rivers and natural drainages. This compounds the problem for a city already struggling with water security and a scarcity of freshwater.
Delhi’s Yamuna: A critical pollution hotspot
Among India’s 311 polluted river stretches, Delhi’s 22 km stretch of the Yamuna between Wazirabad and Okhla barrage is the most toxic. Despite covering only about 2 per cent of the river’s total length, it accounts for 79 per cent of its total pollution load. Recently, concerns have also emerged about high ammonia levels upstream of the Wazirabad barrage, where Delhi sources its raw drinking water—an area that should remain unaffected by the city's untreated sewage. This stretch has become a stark emblem of environmental neglect, raising urgent concerns about the capital’s water security.
To assess the river’s toxicity levels, researchers from the Council on Energy, Environment and Water (CEEW) conducted water quality testing upstream of the Wazirabad barrage – right before the river is diverted to the raw water treatment plant (Figure 2).
Figure 1: Location of Wazirabad raw water treatment plant and sampling location
Source: Authors’ analysis
How We Tested the Water
Using the grab sampling technique, our researchers collected the samples twice a day (morning and evening) for three consecutive days (1–3 February 2025). The sampling site remained the same throughout the sampling duration as source composition was expected to remain constant for a particular season (pre-monsoon and post-monsoon). Morning samples were collected between 10 am and 10:30 am and evening samples were collected between 5:30 pm and 6 pm. A total of six samples were collected and tested for 14 parameters, categorised as follows:
The samples were collected following CPCB protocols for water quality testing and analysed by a lab accredited by the National Accreditation Board for Testing and Calibration Laboratories (NABL).
The WQI was then computed based on four key parameters—pH, BOD, faecal coliform, and dissolved oxygen—using CPCB methodology. However, additional scrutiny was given to biological oxygen demand, free ammonia (N) and ammoniacal nitrogen (NH4-N),as they exceeded permissible limits.
Figure 2: CEEW researcher collecting water samples from river Yamuna
Findings : a conflicting narrative
The average WQI computed was 63.62 out of 100, classifying it as ‘good to excellent’ (Class A). These tests followed CPCB's methodology, which are based on a modified National Sanitation Foundation (NSF) Water Quality Index (WQI) approach. On paper, this suggests water quality suitable for drinking after treatment.
Table 1: The average WQI of Yamuna falls under the ‘good’ to ‘excellent’ category
Source: Authors’ analysis based on data collected from CEEW sampling
Limitations of WQI: The ammonia problem
The single value obtained through WQI after normalising different parameters, should further be understood in terms of the contribution made by every single parameter. For instance, in this case, despite the promising WQI score, the river’s BOD levels remained persistently high at 4.5 mg/l (Figure 3), exceeding Class A limits. High BOD indicates excessive organic pollution, which depletes dissolved oxygen and harms aquatic life.
Figure 3: The BOD value exceeds the criteria for category A and B designated water use
More alarmingly, ammoniacal nitrogen (NH4-N) levels reached 2.3 mg/l—far above the acceptable limit of 0.5 mg/l and exceeding the treatment threshold of the water treatment plant at 1 mg/l (Figure 4). However, the WQI does not factor in ammonia levels (as measured as NH4-N), despite its critical role in assessing river health. Ammonia pollution is primarily linked to agricultural runoff, industrial discharges, and untreated sewage from upstream states like Haryana and Uttar Pradesh. This is a major concern, as excessive ammonia levels can disrupt water treatment operations and cause supply shortages.
Figure 4: Ammoniacal nitrogen concentration was beyond the acceptable limit across all three days of sampling
High levels of ammonia (NH4-N) pose both health and water availability implications. For instance, Panipat, located around 85 km upstream and known for its textile and dyeing industries, releases a toxic mix of untreated chemicals into the Yamuna, severely deteriorating its water quality. This pollution has led to a surge in water-borne diseases, including kidney malfunction, enamel erosion, and skin disorders. Between December 2024 and January 2025, the Delhi Jal Board reported that ammonia levels exceeded 3 mg/l on 39 out of 58 days, far surpassing Delhi’s treatment capacity of 1 mg/l. As a result, water treatment plans had to scale down operations, leading to a 5-10 per cent reduction in supply, significantly impacting areas like Majnu Ka Tila, Defence Colony, and Greater Kailash.
What is driving high ammonia levels?
Several factors contribute to these frequent surges in levels of ammoniacal nitrogen (NH4-N) in the Yamuna, especially in the stretch of the river between Haryana and Delhi:
Restoring Yamuna’s water quality
Addressing the city’s water crisis and ensuring the river’s long-term health demands a comprehensive strategy that tackles pollution at the source, enhances used water treatment, strengthens monitoring systems, and ensures better governance.The following measures need to be undertaken to ensure this:
Surat, located on the banks of the Tapti River, has demonstrated how this can be done. In 2019, the city adopted a dedicated TUW reuse plan, and by 2024, the Surat Municipal Corporation had supplied 1,73,129 million liters of recycled water–achieving over 30 per cent TUW reuse and generating revenue of INR 490 crore (USD 56.3 million) in revenue. Additionally, during non-monsoon periods, Surat releases around 155 million liters per day of secondary-treated wastewater into the Tapti river to maintain its ecological flow. Similarly, industrial towns in Haryana should adopt a dedicated action plan for mainstreaming TUW and ensure that treated water is discharged into the Yamuna during lean seasons to sustain its ecological balance.
Delhi’s vision for a clean and thriving Yamuna cannot be realised without tackling the fundamental causes of its pollution. A science-driven, policy-backed approach that focuses on improving river health assessments, developing dedicated river rejuvenation plans, and harnessing emerging technologies for the treatment and real-time monitoring of ammonia levels is essential to restoring the river and ensuring Delhi’s water security in the years to come.
Kartikey Chaturvedi and Ayushi Kashyap are Research Analysts and Trisha Ravindranath is a Research Intern at the Council on Energy, Environment and Water (CEEW). Send your comments to [email protected].
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