Lack of annual flush leaves Yamuna highly polluted this year

New Delhi
This year, the water level of the Yamuna failed to cross the warning level of 204.5 metres at Old Railway Bridge, a first since 2014 and only one of six instances recorded since 1963. This means the river did not go through a single flooding cycle, missing out on the annual flush in the highly polluted stretch between Wazirabad and Okhla, and lack of aquifer recharge, experts say. High pollution load, untreated effluents from industries and domestic sewage are now playing out with meteorological factors as scenes of iceberg-like foam blocks floating on the river surface.
For a river such as the Yamuna, the four-month monsoon cycle when low-level flooding occurs is critical for annual cleaning, when the river flows from mouth to tail in one flow. It helps to maintain a continuous flow, improves aquatic life during this period and also helps recharge the underground aquifers on the floodplains.
To be sure, this flooding does not stop froth formation, but ensures improved river health.
Although Delhi received 63% additional rainfall this year, the Yamuna level did not cross the danger mark.
Experts said that besides rainfall, there are multiple factors at play that affect the water level of the Yamuna. Key among these is lower rainfall in the upper catchment areas of the river and its tributaries, controlled discharge from the Hathnikund barrage, as well as a series of precautionary measures, such as opening of all barrage gates to prevent recurrence of flooding, a senior Irrigation and flood control (I&FC) department official said.
“Besides the river levels at Old Railway Bridge, the flood warning is also issued when more than 1 lakh (100,000) cusec of water is released from Hathnikund barrage. The peak discharge this year during monsoon only reached 87,071 cusec, that too on one occasion. In comparison, last year, the discharge level crossed 3.5 lakh (350,000) cusec mark,” the official, not wishing to be named, said.
An official from Haryana irrigation department said: “Water in Yamuna at Hathinikund barrage primarily comes from two tributaries in Himachal Pradesh and the catchment area of Haryana. Bata tributary meets Yamuna near Bata Mandi; Giri originates in the Kotkhai hills, flows through Sirmaur district of Himachal Pradesh and meets the Yamuna near the border of Uttarakhand. This year, not much water came into the Yamuna from these rivers.”
Rainfall data from the India Meteorological Department shows that of 15 districts where the upper tracts of the river and its tributaries lie, 12, including Simaur, Solan and Uttarkashi, received below-normal rainfall.
According to I&FC data, there have only been six occasions since 1963 when lower maximum levels have been observed — in 1984 (204.15m), 1987 (202.51m), 1991 (203.36m), 2004 (203.72m), 2006 (204.1m) and 2014 (204m).
In the past 62 years, the warning level has been breached in 53 of them, making it a common annual occurrence.
Bhim Singh Rawat, a Yamuna activist and member of the South Asia Network on Dams, Rivers and People (SANDRP) said the lack of fresh water being released in the river and high pollution level also highlight the issue of ecological flow of the river now being maintained. “The river is dead because no water is being released into it. Low to medium flood level is an annual phenomenon and the river has rarely been this dry in the last decade. For a river like the Yamuna, the four-month monsoon cycle is critical for annual cleaning, when the river flows from mouth to tail in one flow — unlike the fragmented polluted river for remaining eight months. It is also crucial for recharging the floodplains and aquifers,” he said.
According to Delhi Pollution Control Committee (DPCC), faecal coliform levels, an indicator of sewage entering the river, reached a record 4,900,000 MPN (most probable number)/100 ml in September. This was 1,959 times higher than the standard of 2,500 MPN per 100 ml, indicating the annual flush-out did not occur this year.
Rawat said that the state of the river also brings the issue of e-flow under the spotlight.
“An ecological flow of 23 cumec (1cumec = 35 cusec) has been recommended by National Institute of Hydrology as well as the parliamentary standing committee on water resources, but the river only get less than 10 cumec water. Besides the low rainfall, less water is being released from the Hathinikund barrage. A 15-day release before Chhath could also provide a temporary relief from frothing due to dilution,” he said.
Diwan Singh, an activist who took up the cause of Yamuna protection in 2007, said: “Flooding recharges the aquifers in the river floodplains. More the flooding cycle, better the river health. Monsoon months are the only time when the river flows in its natural form. Otherwise, beyond Wazirabad, the river is almost dead.”