Domestic and industrial water is still dominated by groundwater. Overexploitation has led to a sharp decline in the groundwater level, an imbalance in the surface ecology, and more and more serious environmental problems. The rational use of the original transparent soil surface and the maximum maintenance of the original natural state have become the focus of human beings.
Every summer, China's cities are frequently hit by heavy rainstorms, and the "level" of rain disasters is increasing year by year, and reports of once in ten years, once in fifty years or even once in a century continue to impact people's eyeballs. I do not want to discuss how many years the rain disaster belongs to the level of once in many years, but after the rainstorm, there is a serious flooding phenomenon in various cities, resulting in traffic jams, power outages, and flooded houses. Experts pointed out that the main reason for this situation is that the road surfaces in China's cities are impervious.
In urban construction, many cities use a large number of closed surfaces such as cement, asphalt, and concrete to replace the original soil surface; for public places such as sidewalks, open-air parking lots, courtyards and squares, they also like to lay with neat and beautiful stone slabs or cement colored bricks. While improving traffic and road conditions and beautifying the environment, closed surfaces also have a significant adverse impact on urban ecology and climatic environment:
Cities become "man-made deserts". Closed surfaces and high-rise buildings make the surface of modern cities gradually hardened and covered by water-blocking materials, and it is difficult for water to penetrate down, and precipitation soon becomes surface runoff, entering rivers or underground drainage pipes, forming an ecological "artificial desert".
The urban "heat island effect" is serious. Impermeable pavement lacks the ability to regulate the temperature and humidity of the urban surface, the rain evaporates quickly, the surface is easy to dry, and the dust pollution is heavy; and the water evaporates rapidly after the rain, and the air humidity is large, making people feel sweltering and unbearable, and then it is abnormally dry, resulting in the meteorological urban "heat island effect".
The water table is "funnel-shaped". Impermeable pavement prevents groundwater recharge routes, coupled with excessive extraction of urban groundwater, resulting in lower and lower urban groundwater levels, triggering ground subsidence, and coastal areas leading to seawater inversion; resulting in geological "funnel-type" groundwater levels.
Cities are full of "dead ground". The hardened impermeable ground makes it difficult for the surface plants used to regulate the microclimate in the city to grow, and some trees even die and fall due to root lack of water, thus losing their ecological role. Surface runoff has a serious impact on the quality of urban surface water. Due to the large amount of dust and various pollutants on the surface of the city, the runoff formation process washes the surface, but these pollutants are also quickly brought into the urban river channel.
Conversely, permeable pavement can balance urban ecosystems. Rainwater seeps into the ground from the permeable pavement, causing the groundwater level to rise rapidly. The permeable ground can also penetrate the "ground gas", so that the ground is warm in winter and cool in summer, permeable in the rainy season, and snow in winter, which can increase the comfort of urban living. In addition, due to the large surface gap and large surface area of the permeable ground, there is a strong adsorption force for dust, which can reduce dust pollution and reduce noise. Some developed countries have begun to research and develop permeable pavement materials since the 1970s, and have applied them to courtyards, sidewalks, bicycle paths, public squares, open parking lots, roads in parks and both sides of roads and central barriers
The city's water-permeable and breathable space has achieved good results in regulating the urban microclimate and maintaining ecological balance. Since the 1990s, the use of permeable materials to replace traditional materials to pave the road has become a common experience in urban construction in developed countries. For example, Germany, which is known for its environmental protection technology, proposed to transform 90% of the pavement of cities in the country into permeable pavement by 2010.
The construction of sponge cities should follow the principle of ecological priority, combine natural routes with artificial measures, and maximize the accumulation, infiltration and purification of rainwater in urban areas under the premise of ensuring the safety of urban drainage and flood prevention, and promote the utilization of rainwater resources and ecological environmental protection. The construction of a "sponge city" is not to reinvent the traditional drainage system, but to "reduce the burden" and supplement the traditional drainage system, and maximize the role of the city itself. In the process of sponge city construction, the systematization of natural precipitation, surface water and groundwater should be coordinated, and the various links of water recycling such as water supply and drainage should be coordinated, and their complexity and long-term nature should be considered.
As an important symbol of the transformation of urban development concepts and construction methods, the "timetable" for the construction of sponge cities in China has been clear and "can only go forward, not backward". More than 130 cities across the country have formulated sponge city construction plans.
The core of the target set is to make 80% of the rainfall absorbed and utilized on the spot through the construction of sponge cities. The timeline set around this goal is for 2020 for 20% of urban built-ups to meet this requirement. If a city has a built-up area of 100 square kilometers, at least 20 square kilometers will meet this requirement in 2020. By 2030, 80% of urban built-up areas will meet this requirement.
To build a sponge city, we must first reverse the concept. The traditional urban construction model is full of hardened pavement. Whenever there is heavy rain, it mainly relies on "gray" facilities such as pipes and canals and pumping stations to drain water, and takes "rapid elimination" and "end concentration" control as the main planning and design concepts, which often causes floods when it rains, and drought and floods turn sharply. According to the "Technical Guidelines for sponge city construction", urban construction will emphasize the priority use of "green" measures such as grass ditches, rain gardens, and sunken green spaces to organize drainage, with "slow discharge and slow release" and "source dispersion" control as the main planning and design concepts.
To build a sponge city, there must be a "sponge body". The urban "sponge" includes water systems such as rivers, lakes and ponds, as well as urban supporting facilities such as green spaces, gardens, and permeable roads. Rainwater seeps down, stagnates, purifies and reuses through these "sponges", and finally the remaining part of the runoff is discharged through the pipe network and pumping station, which can effectively improve the standard of the urban drainage system and alleviate the pressure of urban waterlogging.
1, permeable pavement: as a new environmental protection, ecological road materials.
2. The colored permeable pavement prevents the road area from being watery, and does not reflect light at night, increasing the safety and comfort of the pavement.
3. The permeability of the permeable concrete pavement can make the rainwater quickly infiltrate into the ground, restore the groundwater, maintain the soil moisture, maintain the ecological balance of groundwater and soil, and avoid the sinking of the foundation caused by over-exploitation of groundwater.
4. The permeable pavement has a unique pore structure, which is close to the ground covered by natural vegetation in terms of heat absorption and heat storage functions, adjusts the temperature and humidity of urban space, and alleviates the urban heat island effect.
5. The porosity of the permeable pavement is large, which has the effect of sound absorption and can reduce environmental noise.
6. A large number of gaps in the permeable pavement can adsorb urban pollutants (such as dust) and reduce dust pollution. And easy to maintain, just with the method of washing with high pressure water, you can deal with the problem of porosity blockage.