|Project Details||The dam was completed in 1952 as part of a campaign to “Harness the Huai River” and its tributaries after severe flooding in previous years. During the 1950s, over 100 dams and reservoirs were built just in Zhumadian Prefecture of Henan Province along with Banqiao. When the Great Leap Forward began in 1958, the campaign was held up as a national model to “give primacy to water accumulation for irrigation." . The total capacity of the reservoir was 492 million m3 with 375 million m3 reserved for flood storage. The dam was made of clay and was 24.5 meters high. The maximum discharge of the reservoir was 1742 m3/s. Cracks in the dam and sluice gates appeared after completion due to construction and engineering errors. They were repaired with the advice from Soviet engineers and the new design, dubbed the iron dam, was considered unbreakable. Chen Xing (陈惺), one of China's foremost hydrologists, involved in the design of the dam, was also a vocal critic of the government's dam building policy, which involved many dams in the basin.|
The dam was designed to survive a once-in-1000-years flood (300 mm of rainfall per day) but a once-in-2000-years flood occurred in August 1975, following the collision of Typhoon Nina and a cold front. The typhoon was blocked for two days before its direction ultimately changed from northeastward to westward. As a result of this near stationary thunderstorm system, more than a year's worth of rain fell within 24 hours (1060 mm), exceeding the average annual precipitation of about 800 mm. The Banqiao Reservoir was designed with a capacity of only 492 million cubic meters but it had to accommodate more than 697 million cubic meters of floods, with half the recommended gates.
The cascade of dams that had been built on the Huai River and its tributaries to reduce flood risks ultimately made the flooding deadlier and the rescue effort more difficult. "Henan Flood Disaster in August 1975", the government-sponsored book, records the deadly flood with stark figures. “Two large dams, Banqiao and Shimantan, plus two medium-sized and 58 small ones were broken down by the flood. Nearly 10 billion cubic meters of water created 10-meter-high waves and ravaged the whole Zhumadian area in a matter of hours. More than four million people in 30 counties were trapped in the water, with five million houses and one million animals washed away"