During the recent Delhi assembly elections, the polluted waters of the Yamuna became a campaign issue. The new government in the Capital must make river-cleaning a priority. While the immediate cleaning operations include trash skimming, weed harvesting and dredging, these will have to be long-term, overarching the entire region. The river zone in Delhi covers 9,934 hectares and the river flows along a length of 48 km. It is flanked by the river Hindon in the east and the Sahibi (Najafgarh drain) in the west.

The Yamuna is integral to Ganga riverine system. The river zone in Delhi has been used for power stations, samadhis, housing, offices, stadia, temples, cremation ground, an IT park, and illegal sand mining. More than 161 unauthorised colonies have come up in this zone which discharge their daily effluents and waste into the river. These have altered the river regime and endangered its water quality.

During the last 50 years, freshwater vertebrates in the river have declined by 83%, groundwater has depleted, and there is a serious loss of biodiversity. The embankments and construction have constricted the water flow, resulting into frequent flooding. With indiscriminate urbanisation, industries, unsewered colonies, fly ash and garbage dumping, the river has become a corridor of filth, garbage, squatting and insanitation.

About 90% of Yamuna water is diverted into drains and canals upstream, leaving it quite dry, especially during the summer. Without continuous flow, parts of the river become stagnant and highly polluted. Against the present environmental flow (e-flow) of 0.86 million cubic metre/day, the Yamuna in Delhi needs minimum 6.6 mcm/day. The Supreme Court, in 1999, directed that a minimum10 cumecs of water be ensured throughout, together with pollution abatement and up-gradation of water quality to meet the burgeoning demand of water supply.

Nearly 75% of Yamuna pollution is from sewage, with the balance comprising industrial effluents, run-off from agricultural fields, solid waste dumps, and open defecation, among others. According to the Delhi Pollution Control Committee, 28 major drains empty into the Yamuna in Delhi, disposing sewage and waste. Against the disposal of 792 million gallons per day (mgd) of sewage, the current treatment capacity is only 550 mgd. New sewerage treatment plants (STPs) have been planned at Okhla, Sonia Vihar, and Delhi Gate besides rehabilitation of three STPs at Kondli Phase II, Rithala Phase I and Yamuna Vihar Phase II.

Besides 31 planned industrial areas, the Delhi government, in 2005 and 2006, regularised 23 non-conforming industrial clusters. These are without any safeguards for effluent disposal. There is microplastic contamination of the river water as well.

The Gazetteers of Delhi 1883 and 1912 state that there were 65 species of fish in the river such as mahseer, rohu, bachwa, mullet, tengra, Silond catfish, mohi (Chital knifefish), mrigal carp, lalbans, chilwa, goonch catfish, and catla, besides different turtle and crocodile species. History books mention boating along the course of the river, from Delhi to Agra and further ahead.

The National Green Tribunal (NGT) last month reminded the Delhi Development Authority (DDA) of non-compliance of its 2019 order to remove encroachments from the Yamuna floodplain and the delay in Yamuna floodplain demarcation based on a one-in-100-year flood probability model. The Delhi government, last year in September, had informed the NGT that a committee comprising the district magistrate, DDA, and the revenue department had been formed to assess the encroachments on the Yamuna floodplain, and the demarcation of flood zone was in progress. Orthorectified aerial images had been generated by interpretation of drone images, and ground surveys by the joint teams have been submitted to the Geo-Spatial Delhi Limited (GSDL).

Floodplain demarcation has been hanging fire since the 1978 floods in Delhi. The Yamuna Standing Committee, in 1978, recommended that the minimum spacing between future embankments of the river be five km and the embankments be aligned at a minimum distance of 600 m from the “active river edge”.

In the Draft Delhi Master Plan 2041, the floodplains were sub-divided into Zone O-I and Zone O-II. While no construction would be permitted in Zone O-I or the river (6,295 hectares), regulated development will be allowed in O-II (3,638.36 hectares). This will reduce the drainage capacity of the river a third. It will also have serious ecological consequences, besides increasing the frequency and extent of flooding.

The river is intimately connected with the Capital’s water supply, sanitation, flooding, drainage, and transport networks. As such, several agencies dealing with the environmental management and pollution control, land, water, flood control and drainage. power, irrigation, transport, and sewerage need to work together. To that end, the Unified Centre for Rejuvenation of River Yamuna (UCRRY) was notified in July 2015, under the chairmanship of the lieutenant-governor.

The Centre for Science and Environment, under the Namami Ganga Mission, published a Handbook for Planning and Designing Water Sensitive Cities for the Ganga Basin (2023). It stresses that the conservation of existing 1,045 water bodies and wetlands are essential for ecological sustainability. Intach has suggested installation of aeration and bioremediation systems to increase dissolved oxygen in water.

Circulatory water management focuses on the principles of reduce, reuse, recycle, restore, and recover. Decentralised Wastewater Treatment System (DEWAT), bioswales and revival of water bodies are important tools for this. Recycling of wastewater and zero run-off drainage with the provision of swales and retention ponds can help optimise surface and groundwater. Adoption of new technologies, such as blockchain and SCADA systems, can also help in circulatory water management.

The lakes, water bodies, and riverfront can be rejuvenated and landscaped by recycled carbon neutral materials, planting and water recycling strategies. The soft landscape and vegetation along the riverbank allow rainwater to be absorbed rather than running off. Natural in-stream elements, e.g. root wads, provide slow-water habitat for fish and insects that regenerate native wetlands and conserve river biodiversity.

Apart from the budget sources, blended green, social and sustainability bonds (BGSSB) can be explored for financing the clean-up of the river. The Yamuna Project should work closely with the National Mission for Clean Ganga (NMCG) and River Cities Alliance (RCA). Their experience can provide important lessons for infusing life into the Yamuna again.

AK Jain is former commissioner (planning), Delhi Development Authority. The views expressed are personal