China’s military has blasted a dam to release floodwaters threatening one of the country”s most heavily populated provinces, as the death toll from the widespread flooding rose to at least 33.The dam operation was carried out late Tuesday night in the city of Luoyang, just as severe flooding overwhelmed the Henan provincial capital of Zhengzhou, trapping residents in the subway system and stranding them at schools, apartments and offices.Another seven people were reported missing, provincial officials said at a news conference.The equivalent of a year’s worth of rain in three days swallowing up an underground line and turning streets into rivers. A video posted on Twitter by news site The Paper showed subway passengers standing in chest-high muddy brown water as torrents raged in the tunnel outside.A blackout shut down ventilators at the First Affiliated Hospital of Zhengzhou University, forcing staff to use hand-pumped airbags to help patients breathe, according to the city’s Communist Party committee. It said more than 600 patients were being transferred to other hospitals.A woman aboard a subway in a flooded tunnel told her husband the water almost reached her neck and passengers had trouble breathing, the Henan Business Daily newspaper reported.It said staff at a subway station told her husband all passengers had been evacuated but acknowledged that wasn’t so after he started a video chat with his wife on his cellphone showing she still was aboard.The precise times and locations of the deaths and disappearances weren’t immediately clear, although the province said more than 100,000 people have been evacuated to safety. In the face of the scale of the disaster, President Xi Jinping on Wednesday called for mobilisation after the “extremely serious” floods.The government has released 100 million yuan (€13 million) in emergency aid for Henan.More than 200,000 hectares of crops have been swallowed up, the damage is estimated at 1.22 billion yuan (€160 million), according to the authorities.Henan province has many cultural sites and is a major base for industry and agriculture. It is crisscrossed by multiple waterways, many of them linked to the Yellow River, which has a long history of bursting its banks during periods of intensive rainfall.State media on Wednesday showed waters at waist height, with rain still coming down.To the north of Zhengzhou, the famed Shaolin Temple, known for its Buddhist monks’ mastery of martial arts, was also badly hit.The national weather service is forecasting more rain before a lull on Friday. But further north, in Hebei, the province surrounding Beijing, some areas have been placed on red alert. China routinely experiences floods during the summer, but the growth of cities and conversion of farmland into subdivisions has worsened the impact of such events.The impact of climate change is being cited as the reason for the floods, the most severe recorded in the region since records began 60 years ago. U.N. Secretary-General Antonio Guterres sent a letter President Xi Jinping “to convey his heartfelt condolences on the tragic loss of lives and devastation,” U.N. deputy spokesman Farhan Haq said Wednesday.