The Supreme Court on Thursday directed the Himachal Pradesh government to release on Friday 137 cusecs of water it has in surplus, to resolve the drinking water crisis in Delhi. It asked Haryana to do the necessary to facilitate the water’s flow into the national capital.

This came after the AAP government in Delhi had approached the Supreme Court for the same, amid a surge in water demand during last month’s prolonged heatwave. AAP blamed the BJP-government in Haryana for “stopping” Yamuna’s water supply to the national capital.

Where does Delhi’s water come from?

Delhi gets most of its water from the Yamuna, Ravi-Beas, and Ganga rivers.

From the Ganga, via the Upper Ganga Canal in UP, Delhi receives 470 cusecs (roughly 254 MGD) of water.

Two channels entering Delhi from Haryana — the Carrier Lined Channel (CLC) and the Delhi Sub Branch (DSB) — supply Delhi with water from the Yamuna and Ravi-Beas rivers. Delhi receives 719 cusecs of water through the CLC, a lined channel meant to reduce seepage-induced water loss, and 330 cusecs through the DSB (total of roughly 565 MGD). The Delhi Jal Board (DJB) also takes water directly from the Yamuna to try and meet demand. A senior DJB official said Delhi is not allotted any specific amount of water it can draw directly from the river. Put together, Yamuna water — through the CLC, DSB and directly from the river — provides a supply of 612 MGD to Delhi.

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Finally, the DJB supplements its river-water supply with ground water — around 135 MGD of which are drawn from Delhi’s tubewells and ranney wells.

What triggered Delhi’s water shortage?

The water treatment plant (WTP) in North Delhi’s Wazirabad was functioning below its capacity from May 12 to 14, and again from May 18 to June 1. Coincidentally, this was the time when the national capital experienced record high temperatures, and thus, a Steep surge in demand for water.

The Wazirabad WTP has a capacity of 131 MGD (million gallons per day), and serves parts of north, central and south Delhi including Burari, Model Town, Sadar Bazar, Chandni Chowk, Matia Mahal, Ballimaran, Punjabi Bagh, the areas around Rajghat. and ITO, and some parts of Greater Kailash, Defense Colony and South Extension.

It is the third largest of DJB’s nine WTPs in terms of capacity, and primarily depends on water from the CLC and DSB. Officials in both Delhi and Haryana told The Indian Express that this supply was being maintained. But, the plant, which lies on the bank of Yamuna, also draws some water directly from the river, at the Wazirabad reservoir. This is where DJB’s supply problems lie (more on that later).

In May, Wazirabad’s production fell to as low as 102.9 MGD, returning to its normal capacity only on June 2 (131.14 MGD, according to DJB’s bulletin). Other WTPs, however, functioned above their capacity, save for some days of the month when some plants dealt with short power failures. DJB’s bulletins from June 3 to 6 show that the Wazirabad WTP is currently producing around 133-134 MGD per day, slightly more than its capacity.

With all its WTPs functioning as intended, the DJB can produce a little over 1000 MGD of water (DJB’s June 6 bulletin reported production of 1,003.05 MGD). Production had dipped to as low as 966 MGD in May, on a day in which in addition to the Wazirabad WTP, the Sonia Vihar WTP was also functioning below capacity due to a power failure.

But even at full capacity, DJB is not capable of meeting the city’s requirement of 1290 MGD during peak summers, as estimated by the Economic Survey for 2023-24.

Why was the Wazirabad WTP functioning below capacity?

Across the states of Himachal Pradesh, Punjab, Haryana, and Delhi recorded large rainfall deficits from May 1 to 24, according to the India Meteorological Department (IMD).

Scant rainfall meant that the Yamuna simply did not have enough water for the DJB to draw from the Wazirabad reservoir, a DJB official explained. Against a ‘normal’ level of 674.5 feet (above sea level), the water level at the reservoir on May 31 was 670.3 feet. It has risen to 671 feet in the last few days.

This is not the first time such a situation has arisen. In previous summers, the water level at the Wazirabad reservoir has been even lower. In June 2022, for instance, it had reached a level of 667.7 feet.

Apart from low rainfall, the water levels are also impacted due to losses in transit, due to seepage, as well as due to evaporation. An official at the Haryana Irrigation and Water Resources Department said that of the 352 cusecs of water released from the Hathnikund barrage in the summers, a decent proportion is lost in transit.

How much water is Delhi allotted from the Yamuna?

A water sharing agreement on the ‘surface flow’ of the Yamuna among Haryana, Uttar Pradesh, Rajasthan, Himachal Pradesh and Delhi in 1994, specified that Delhi is to get 0.076 billion cubic meters of water from March to June. The annual allocation for Delhi is 0.724 BCM. This amounts to roughly 435 MGD. This allocation is regulated by the Upper Yamuna River Board, with the 1994 agreement due for revision in 2025.

In 1996, in a matter on Delhi’s residents not getting enough water, the Supreme Court had said: “…We order and direct that Delhi shall continue to get as much water for domestic use from Haryana through river Jamuna which can be consumed and filled in the two water reservoirs and treatment plants at Wazirabad and Hyderpur. Both the Wazirabad and Hyderpur reservoirs shall remain full to their capacity from the water supplied by Haryana through river Jamuna.”