Seepage—Because the underlying surface of the city is too hard, there is cement everywhere, which changes the original natural ecological and hydrological characteristics. Therefore, we must strengthen the natural penetration and put the penetration first. It can avoid surface runoff, reduce the collection of cement ground and pavement into the pipe network, and at the same time, conserve the groundwater and supplement the shortage of groundwater. It can also purify the water quality through the soil and improve the urban microclimate. There are various methods for infiltrating rainwater, mainly changing various pavement and ground pavement materials, transforming roof greening, adjusting the vertical of green space, leaving rainwater from the source and then "seeping" it down.
Storage-that is, to leave the rain, we must respect the natural topography, so that the rainfall can be scattered naturally. Now that artificial construction has destroyed the natural topography and landforms, water has gathered in one place within a short period of time, and waterlogging has formed. Therefore, it is necessary to accumulate rainfall in order to achieve regulation and staggered peaks. At present, there are no fixed standards and requirements for the water storage link of the sponge city. There are various types of underground water storage. There are two general types of common storage: underground storage tanks and plastic module storage.
Stagnation-Its main function is to delay the runoff of rainwater formed in a short time. Through micro-topography adjustment, let rainwater slowly gather in one place, and use time to change space. By "stagnation", the peak of runoff can be delayed. The specific forms are summarized in three types: rainwater gardens, ecological detention ponds, infiltration ponds, and constructed wetlands.
Net-Purification of water quality through soil penetration, vegetation, green space system, water body, etc. Rainwater purification systems are generally divided into three categories according to different regional environments: rainwater collection and purification in residential areas, rainwater collection and purification in industrial areas, and rainwater collection and purification in municipal public areas. Different rainwater purification links can be set according to these three regional environments, and the more familiar purification process at this stage is divided into three links: soil infiltration purification, artificial wetland purification, and biological treatment.
Use-The rainwater after the soil infiltration purification, artificial wetland purification, and biological treatment multilayer purification should be used as much as possible. Whether it is a high-water area or a water-scarce area, the use of rain water resources should be strengthened. Not only can it alleviate the flood disaster, the collected water resources can also be used, such as collecting and purifying the rainwater above the parking lot for car washing. We should conserve by "seeping", leaving water in place by "storing", and then "using" water in place by purification.
Drainage—Using the combination of city vertical and engineering facilities, drainage and waterlogging prevention facilities combined with natural water channels, surface drainage and underground rainwater pipes to achieve general discharge and discharge of excess rainwater, to avoid disasters such as waterlogging. Part of the rainwater collected after purification by rainwater gardens, ecological retention areas, and infiltration ponds is used for green irrigation and daily life, and part of it is used to recharge groundwater through infiltration, and the rest is discharged into rivers through the municipal pipe network. Not only does it reduce the chance of water accumulation when the peak of rain is too high, but also reduces the direct pollution of water sources in the first place.