Focus Interview丨From "Ecological Tragedy" to Xiushui Yangyang Technology Empowering Nanhu Butterfly Transformation
It can be seen from the two photos taken from the same perspective of South Lake in Jiaxing, Zhejiang in 2016 and 2021 that the changes in water quality have been clearly visible five years apart. Today, the water of Nanhu Lake is full of rippling water plants and clear blue waves. In the past seven years or so, the water quality of Nanhu Lake has been improved from the previous Class V to the current Class III water in the lake and reservoir. How did this change happen?
In early summer, aquatic plants are still being planted in many rivers and ponds in Jiaxing.
Jiang Xia, director and researcher of the Institute of Lake Ecology and Environment of the Chinese Academy of Environmental Sciences: For relatively mobile seeds that are washed away, we may use cuttings. For better water bodies, we have some seed-throwing methods. Methods can also be planted.
Today's Jiaxing South Lake is green and clear, and the changes in water quality are related to the aquatic plants planted one by one that take root and grow at the bottom of the water. Seeing this, don't think that the water quality of Nanhu Lake has become the current Class III water of the lake and reservoir, just by planting aquatic plants. It took nearly 7 years simply to provide a safe water environment for these aquatic plants.
Jiaxing is located in the lower reaches of the Taihu Lake Basin and in the heart of the Hangzhou-Jiaxing-Huzhou Plain. It faces the sea to the east and the Qiantang River to the south. More than 110 kilometers of the Beijing-Hangzhou Grand Canal passes through Jiaxing. There are more than 200 rivers in the city, with criss-crossing water systems and numerous lakes. The water area accounts for 12% of the entire city. Nine radial water systems connect the Nanhu Lake in the center.
Among Jiaxing’s water sources, 80% is transit water, entering from Wujiang, Huzhou and Hangzhou respectively. For a long time in the past, the quality of upstream water has seriously affected Jiaxing's water environment. As a granary in northern Zhejiang and a gathering place for textile printing, dyeing, and manufacturing industries, Jiaxing’s water was once regarded as an “ecological disaster” due to complex pollution causes.
In 2016, the country started major scientific and technological projects for water pollution control and treatment during the “Thirteenth Five-Year Plan” period, and Jiaxing’s water environment treatment was one of them. Scientists from more than a dozen scientific research institutions, including the National Academy of Environmental Sciences, stationed in Jiaxing together. On the basis of Zhejiang’s “Five Waters Co-management”, Jiaxing has become a pilot city for water ecological restoration in the country. Time advances to 2020. From pollution control to ecological restoration, Jiaxing has encountered a bottleneck.
Shi Xiaosong, Director of the Jiaxing Municipal Ecological Environment Bureau: There is a provincial-controlled section in the center of Nanhu Lake that has never reached the Lake Reservoir Category III standard. There are several other monitored sections. We can see hope in the treatment process, but we have never seen hope in Nanhu Lake. Because it is the Huku standard, the requirements are higher.
The Lake and Reservoir Class III water standard means that Nanhu not only needs to meet water quality standards, but also needs to have good ecological functions. The nine waters of Nanhu Lake are connected to each other, and its ecological restoration affects the whole body. The Institute of Ecology and Environment of the Yangtze River Delta Research Institute of Tsinghua University in Zhejiang is also one of the scientific research teams of the Jiaxing Water Ecological Restoration Project.
Liu Rui, director of the Institute of Ecology and Environment of the Yangtze River Delta Research Institute of Tsinghua University in Zhejiang: From an ecological perspective, if you want to move towards the third stage, which is ecological restoration and better achieve the improvement of biodiversity, you must first have a good Ecological restoration can only be carried out based on the background, so source control is the most basic guarantee and the most important guarantee, otherwise the effect of ecological restoration will be difficult to maintain.
Regarding the issue of how to quickly judge and control potential and more complex pollution sources, Director Liu Rui's team has two innovations. First, they collected data from the main rivers in Jiaxing City in the past ten years. After detailed sorting and analysis, they formed a database and summarized the changing patterns of water quality and possible pollution characteristics of different rivers under different climatic conditions and external environments. Once a problem occurs on a monitoring section, by comparing the real-time monitoring data with a large database, they can quickly and efficiently locate the river channels and areas that need to be focused on exploration.
In a nearby laboratory, another new attempt is being made: they are compiling a fingerprint library for comparison for possible pollution sources in Jiaxing. Not only do they have to figure out the temperament and character of the water in the river, they also have a way of collecting fingerprints for the river water.
Liu Rui, director of the Institute of Ecology and Environment, Yangtze River Delta Research Institute, Tsinghua University, Zhejiang: The fingerprint information is that there are many substances in the water that can emit fluorescence. If you give it an excitation wavelength, the substance will emit another wavelength, forming a specific fingerprint-like The map comes out.
By comparing the fingerprint of the problematic water sample with the fingerprint database, you can quickly identify all possible pollution source information. Whether it is online monitoring, the compilation and analysis of large databases, or even the use of fluorescence spectra to collect fingerprints, the sonar technology of unmanned ships and the means of surveying underwater sewage pipe networks. None of these technologies alone can be said to be an absolute innovation, but the comprehensive use of this series of methods by scientists in the traceability and precise prevention and control of water pollution is a new attempt to empower the construction of a beautiful China through science and technology. This will bring about changes in management concepts and methods.
Yu Junjie, Director of the Science and Technology Division of the Department of Science and Technology and Finance of the Ministry of Ecology and Environment: With the upgrade of scientific and technological means, the upgrade of instruments and equipment, and the update of governance concepts, now we are moving more from the original end to the process and to the front end. , moving towards early warning, and more advanced advance research and judgment of unknown events, which will bring about many disruptive changes and will have many disruptive changes on our future management model.
During the ecological restoration process of Jiaxing South Lake, the problems of accurate source tracing and source control have been solved, but how to keep these aquatic plants alive is another challenge the scientific research team faces.
Jiang Xia, director and researcher of the Institute of Lake Ecology and Environment of the Chinese Academy of Environmental Sciences: We were also considering how to move the more polluted guest water directly and quickly through the city or drain it out through large encirclements. The water in the area is used as preliminary water to provide a good environment for the growth of aquatic vegetation, but its hydrodynamic conditions are really poor.
Jiaxing is located in a plain river network. The entire urban water area spans more than 100 kilometers from upstream to downstream, but the water level difference is less than one meter. Coupled with the supporting effect of ocean tides on urban water bodies, the water mobility in Jiaxing is extremely poor.
Wang Rongchang, associate professor at the School of Environmental Science and Engineering, Tongji University: This is one of our difficulties, but also a place of wisdom. The water level control in plain river network areas relies on limited water level differences. It is a kind of river network system that catches the tide. Sometimes the water level is high, sometimes the water level is low. When the water level is high, the gate is opened and the water is diverted here. When the water level is low, the water level is diverted here. When it comes down, the water level is preserved.
As a waterlogged city, Jiaxing has a relatively complete flood control system. 54 dams and 5 major hubs surround the main city in the middle. The scientific research team from Tongji University cleverly made use of existing flood control projects to create some water level differences through artificial means, which improved the mobility of water and selectively replenished the high-quality water flowing through Jiaxing's passenger water to the city. The district water network has created the conditions. Simply put, it means keeping the good water and draining the bad water.
Professor Wang Rongchang used the hydrodynamic model they produced based on big data to show the water transfer and water exchange scenarios of the entire urban water network in Jiaxing within the corresponding time period under different plans. As the center point of the water network, Nanhu also realizes the dispatch and transformation of water bodies in this way.
Wang Rongchang, associate professor at the School of Environmental Science and Engineering at Tongji University: Our real challenge is not hydrodynamic simulation, which is relatively mature. Our simulation also adds water quality indicators, so that Nanhu Lake gradually becomes a transparent system. This transparency refers to the monitoring and support of data on the characteristics of the entire water quality, biological characteristics, and ecological characteristics.
Digital intelligence is one of the typical features of technology empowerment for water ecological restoration in Nanhu Lake. Now that the water quality conditions are met, the Institute of Lake Ecology of the Chinese Academy of Environmental Sciences has to solve the final problem.
Jiang Xia, director and researcher of the Institute of Lake Ecology and Environment of the Chinese Academy of Environmental Sciences: Its bottom mud is fluid and very thin. After the boat trip, the disturbance arose and the plants could not take root. In the case of liquid mud and high organic matter, how can I perform phytoremediation?
They used a seemingly simple but very smart approach. In specific areas of the South Lake, priority is given to water bodies that can be restored to aquatic ecology, and some bottom and surface projects are used as auxiliary measures to reduce disturbance, thereby reducing human intervention while improving water transparency.
Jiang Xia, director and researcher of the Institute of Lake Ecology and Environment of the Chinese Academy of Environmental Sciences: This can quickly take root and propagate vegetation.
South Lake is like this. From the edge to the center of the lake, it becomes clearer little by little. Now, the aquatic plants in Nanhu Lake have recovered from three artificially planted species to more than ten, and the number of benthic animals has also reached more than ten. The underwater forest here is already a rich and colorful ecosystem. The successful experience of Nanhu is also radiating the ecological integration process of the entire Yangtze River Delta region. In Jiashan County, the ecologically restored Xiangfudang has become a science and innovation green valley in the Yangtze River Delta region; in Pinghu, water ecological restoration is assisting the construction of beautiful villages and industrial development here.
The beautiful water is clear and the red boat remains the same. This is the process of the entire Nanhu ecological butterfly change.
With a healthy ecological environment, the water quality of Nanhu Lake can be stably maintained at the lake reservoir Class III water standard. Strengthening scientific and technological support is an important part of improving the guarantee system for building a beautiful China. Technology empowers the construction of a beautiful China, and Nanhu is just a microcosm. We see that monitoring is a means, models are a means, and ecological measures are a means, and scientific researchers have organically synthesized these means into a technical system, which also provides useful reference for cross-regional and cross-field ecological and environmental governance. High-level protection and high-quality development are the significance of science and technology empowering the construction of a beautiful China.
