The latest Delhi Pollution Control Committee (DPCC) readings show that Yamuna pollution worsened at two important monitoring points in September despite the arrival of the monsoon. At ISBT Bridge and ITO Bridge, biochemical oxygen demand (BOD), chemical oxygen demand (COD) and faecal coliform levels were all higher than at the corresponding points last year. The pattern is important not simply because the river remained polluted, but because rainfall did not produce the improvement that is often expected from increased water flows.
The figures indicate a river whose measured condition depends on more than rain. At ISBT Bridge, the sample recorded on September 7 this year showed a BOD of 30 mg/l, compared with 8 mg/l on September 3 last year. COD rose from 44 mg/l to 92 mg/l over the comparable period. The reported faecal coliform count increased from 2,800 to 35,000, a 12.5-fold rise.
At ITO Bridge, the deterioration was also substantial. BOD increased from 4 mg/l to 18 mg/l, while COD rose from 20 mg/l to 60 mg/l. Faecal coliform levels moved from 1,800 to 17,000 MPN/100 ml. These are not marginal changes in a single indicator. They show simultaneous deterioration across measures associated with organic pollution, chemical contamination and microbial risk.
The DPCC comparison also provides a useful benchmark for understanding the scale of the problem. A BOD level of 3 mg/l or less and dissolved oxygen of at least 5 mg/l are specified for bathing. The desirable faecal coliform limit is 500 MPN/100 ml, with 2,500 MPN/100 ml described as the maximum permissible level. The reported readings at both monitoring points were therefore far above the stated faecal coliform benchmarks, while BOD was also substantially higher than the specified bathing limit.
These measurements do not establish that every part of the Yamuna experienced the same level of deterioration. They relate to specific monitoring points and dates, and the supplied report does not provide a complete river-wide assessment. But the two locations are significant for interpreting conditions in Delhi because they represent points along the river where pollution levels are being monitored within the city. The evidence is consequently strongest as a warning about the condition recorded at these stretches, rather than as a claim about every kilometre of the river.
The comparison with rainfall makes the findings more revealing. The monsoon brought less rainfall to Delhi in September this year than during the same period last year. At the same time, the report notes that net rainfall was above normal in both 2025 and 2026, while the river did not cross the danger mark this year, unlike last year. This means that the relevant question is not simply whether rain occurred, or whether annual rainfall was above normal. The question is how much water actually moved through the monitored stretches, when it moved, what upstream releases contributed, and how much sewage entered the river during the sampling period.
Rainfall is therefore an incomplete measure of river health. A heavy shower can produce runoff without creating a sustained increase in the river’s flowing volume. Rain can also arrive in short, intense bursts, while pollution readings are taken on particular dates. The timing of rain relative to sampling matters. So does the amount of water released from upstream. The report specifically identifies flowing-water volume, upstream releases, the timing and intensity of rainfall, and the quantity of sewage entering the river as factors that can influence measured pollution levels.
This distinction is central to how urban water pollution should be understood. A river passing through a dense city is not affected only by natural hydrology. Its quality also reflects the performance of the systems connected to it: sewage collection, treatment, drainage, interception and discharge control. The supplied evidence does not identify which of these factors caused the September deterioration. It does, however, show why rainfall alone cannot be treated as proof that pollution should have fallen or as evidence that a river has recovered.
BOD is particularly useful in this context because it indicates the amount of oxygen that microorganisms require to break down organic matter in water. Higher BOD is associated with a greater organic load and leaves less oxygen available for aquatic conditions. COD measures the oxygen required to chemically oxidise pollutants and can capture a broader range of contaminants. Faecal coliform counts indicate contamination associated with human or animal waste. When all three indicators rise together, the results point to a worsening pollution burden in the sampled water, even though the supplied report does not assign that burden to one specific source.
The faecal coliform figures are the starkest part of the DPCC comparison. At ISBT Bridge, the count rose from 2,800 to 35,000 MPN/100 ml. At ITO Bridge, it increased from 1,800 to 17,000 MPN/100 ml. Both current readings were well above the maximum permissible level of 2,500 MPN/100 ml cited in the report. This makes the issue more than an environmental indicator story. It is also a question of how urban residents understand the safety of a river that is monitored against bathing-related standards but remains far outside them at the reported locations.
The findings also expose the limits of judging river-cleaning progress through visible water levels or rainfall events. Last year’s river crossed the danger mark, while this year’s did not. Yet the absence of a flood-level event did not translate into better readings at ISBT or ITO. Water quantity and water quality are related, but they are not interchangeable. A river can carry more water during a flood and still contain significant pollution, while a river that does not cross the danger mark can record high concentrations of pollutants depending on flows and discharges.
For governance, this creates a measurement challenge. Public agencies need to distinguish between the conditions that alter pollutant concentration and the conditions that reduce pollutant loading. Rainfall or upstream releases may change dilution and flow. They do not necessarily remove the sewage entering the river. The supplied report does not provide data on sewage volumes, treatment-plant performance or individual discharge points, so it cannot establish whether those systems failed during the period. It does show that the pollution readings cannot be explained by rainfall totals alone.
The DPCC’s role in this story is significant because the committee’s monitoring provides a basis for comparing water quality across time and locations. Such comparisons are more useful when they are read with their sampling dates, rainfall conditions and flow information. The September readings demonstrate the value of maintaining regular monitoring, but they also show why isolated numbers require hydrological and operational context. Without that context, a rise in BOD or faecal coliform can be reported accurately but understood incompletely.
The institutional question is therefore not only whether the river is polluted. The available data already answer that at the reported points. The larger question is whether the agencies responsible for urban drainage, sewage management and river monitoring can connect pollution readings to specific causes and corrective action. The supplied material does not name those agencies or describe an action plan following the DPCC report. That absence limits what can be concluded about accountability or implementation, but it also identifies the information that matters for the next stage of reporting.
Future assessments would need to show whether the September deterioration was temporary or part of a continuing pattern. They would also need to compare more monitoring points, establish the relationship between sampling dates and rainfall, record upstream releases, and place the readings alongside sewage-entry and treatment data. None of those additional conclusions can be drawn from the supplied report alone. They are, however, necessary to determine whether the reported increase reflects a short-term concentration effect, a rise in pollutant loads, or both.
What the evidence confirms is narrower but serious. At ISBT Bridge and ITO Bridge, the September readings reported by the DPCC were worse than the comparable readings last year across BOD, COD and faecal coliform. The current faecal coliform levels were far above the benchmarks cited for bathing, and BOD was also substantially higher than the specified limit. Rainfall conditions, river levels and pollution readings did not move in the same direction. The next meaningful test will be whether subsequent monitoring shows an improvement and whether authorities can link the numbers to measurable changes in sewage flows, river discharge and treatment performance.
