Liu Yi is the most clever thing is that he gave the Fushou ditch drainage outlets installed 12 water windows. Water window by the outer gate, the inner gate, Dulong Bridge and regulating pool, fully utilizing the principles of hydraulics, when the river rises, with the help of the flood water impulse to make the outer gate from the outside tightly closed, the flood water will not be poured into the ditch.
When the flood receded, the water level fell below the water window, and with the help of the ditch water will be inside the gate open, to ensure the smooth discharge of rainwater. Liu Yi to change the cross-section, increase the slope and other methods, so that the water through the Dulong Bridge into the water window, the flow rate increased steeply by 2 to 3 times, both to wash away the sediment and debris in the water, but also to open the outer gate.
But when the water window is closed, the floodwaters don't back up into the city, but the rainwater in the ditch can't be drained either. In order to solve this problem, Liu Yi will Fushou two ditch and the city's three ponds (as well as dozens of ponds such as Qingshui pond, lotus pond, water spinach pond, garden pond, iron helmet pond, etc.) connected to form a living water system.
When rainwater flows into the ditch to a certain height, the ponds are like huge natural cisterns. And when the water window is opened, the excess water from the ponds will quickly flow back into the ditch and be discharged into the river through the water window, leaving the ponds in their original form.
Expanded Information:
According to the book "Ancient Streets of the City Halls of Ganzhou", compiled by Ganzhou native Xie Zongyao. Streets" book "Ganzhou old town ponds" section recalls: "counted to find 29 places *** 84 ponds. In case of heavy rainfall, can regulate the flow of rainwater, reduce sewer overflow; if the Zhang, Gong two rivers flooding forced the city, the city can not be discharged when the rain and flooding can be adjusted to avoid flooding."
In addition to drainage and flood control, the reservoir also has both fire prevention and greening, improve the urban environment, irrigation nursery farming and other roles. Accompanied by the accelerating urban construction, Ganzhou city ponds less and less, part of the ponds of the storage function is modernized flood pumping machine replaced. Located in Zhanggong of the eight realm park, retained to date the pond has become a good place for people to go boating.