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Rainfall data from areas that feed the Yamuna suggest that these regions received rainfall much higher than the normal range in the days leading up to Wednesday, leading to the rivers that make up the Yamuna river system swelling to unprecedented levels. The Sirmaur and Shimla districts of Himachal Pradesh, for instance, which are major catchment areas for the Yamuna through the Giri and Pabbar rivers, received over 200 mm of rain, double the normal, between July 8 and 10. Uttarakhand’s Uttarkashi district, where the Yamuna originates at the Yamunotri glacier, recorded 202.3 mm of rain between July 6 and 12, 133% more than normal. The Dehradun district, which feds water into Yamuna through smaller rivers such as Asan, Sunheri, Pabbar and Aglar, saw 345.3 mm of rain between July 6 and 12, 139% more than the normal.

All of this meant that the flow of water at the Hathinikund barrage rose steeply between July 10 and 11, forcing Haryana to open the sluice gates. The barrage, built in the year 1996 and operationalised in 1999, to replace Tajewala built in 1873, is located in Yamunanagar, on Haryana’s northern tip, and has ten main gates. Between 2 pm on July 10, the flow of water was 2.13 lakh cusecs, it rose to a peak of 3.59 lakh cusecs at 11 am on July 11.

Since then, the flow of water has reduced steadily; it was 61,019 cusecs at 6 pm on Thursday even, eventually leading to close of the gates at about 6 p.m. on Thursday, which should come as major relief of several districts of Haryana and Delhi, officials said. The decision on re-opening of the gates will be taken depending on water flow from Himachal and Uttarakhand, they said.

The usual average flow of water in July at the barrage is around one lakh cusecs per second.

On Wednesday an alarmed Delhi Chief Minister blamed the water from the barrage for the worsening situation in Delhi and said in a letter to the Union Government, “It has not rained in Delhi for the last three days. The water level in the Yamuna in Delhi is not increasing due to the rains in Delhi, but due to the water released from the Hathinikund barrage located in Haryana.” He asked Union Home Minister Amit Shah to limit the speed of the release of water so that “the level of Yamuna in Delhi does not rise further.”

The problem was that a barrage can’t do this. The Delhi chief minister himself admitted as much later in the evening, when he said that he received a phone call from Union Minister Gajendra Singh Shekhawat who had said Hathinikund was “just a barrage” and had no reservoir to store water. “The water volume being released from Himachal Pradesh has reduced and the situation will improve. But it will take time to reflect in the water level of the Yamuna,” Kejriwal said at a press conference on Thursday evening.

Officials said that heavy rainfall in areas corresponding to the Yamuna river system downstream from the barrage were also a factor in the flooding Delhi has seen. According to India Meteorological Department (IMD), Yamunanagar received 400.6 mm of rainfall between July 6 and 12, almost six times the normal in that period while Karnal received 186.2 mm of rain between those dates, three times the usual. Panipat received 131.3 mm of rainfall, four times the usual.

This also led to several local rivers that rise during the monsoons, such as the Somb and Pathrala that originate from the Shivalik hills, to swell beyond capacity. “It played an important role in sudden increase in Yamuna water,” a senior Haryana government official said.

Himanshu Thakkar, an independent expert who has done extensive work on river systems however added that poor management of the Yamuna river was one of the primary drivers of the floods in Delhi. “Peak flow of water from Hathinikund on July 11 was less than in 1978, 2019 and 2012-13 where it was even upto 9 lakh cusecs showing that the rains in the hills may have had a limited role. It is more because of what is happening in Yamuna flood plains in and around Delhi,” he said. To be sure, in 1978, the job of regulating water flow was done by the Tajewala barrage which was replaced by Hathanikund.

Thakkar pointed out that water absorbtion capacity of Yamuna riverbed has been affected by the muck that is emptied into the river and the rampant sand mining along its banks. “Very little flushing of water is happening because of deforestation along the flood plains and disappearance of water bodies.”

Officials in Haryana said that over the next two days they expect the flow of water in the Hathinikund barrage to increase, but encouragingly, stay below the levels of July 11. This is because after no rain on Tuesday, there was another spell of rainfall in Yamuna catchment areas in Himachal Pradesh and Uttarakhand on Wednesday and Thursday. Dehradun received 62 mm till 8.30 a.m. on Thursday morning, 220% higher than normal. IMD has issued an orange alert for Himachal and Uttarkhand on Friday and red alert for Saturday and Sunday.

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Officials said that rain water from these two states usually takes 24 to 48 hours to reach the plains. “But we don’t expect a June 11 like situation in Delhi again because there is very little rainfall in areas downstream of Hathinikund,” an official said. Another official from the Central Water Commission said that he expects the water level in the Yamuna in Delhi to dip below 208 metres by Friday evening, despite a possible increase in flow from Hathinikund, given the lack of localised sources of rain.