On September 27th, on the day of World River Day, the press conference of "Taking the Pulse of the Yangtze River" and "Yangtze River Vitality Report 2020" (hereinafter referred to as "Report") co-sponsored by WWF and The Paper was held in Shanghai.
In this activity, WWF, together with the Institute of Hydrobiology of Chinese Academy of Sciences, the Institute of Geographical Sciences and Resources of Chinese Academy of Sciences, the Nanjing Institute of Geography and Lakes of Chinese Academy of Sciences, the Yangtze River Academy of Water Conservancy Commission, the Environmental Planning Institute of the Ministry of Ecology and Environment, the Key Laboratory of Yangtze River Water Environment Education Department of Tongji University, the School of Water Conservancy and Hydropower of Wuhan University, and the Suzhou Institute of Environmental Innovation of Tsinghua, jointly released the Yangtze River Vitality Report 2020.
It is understood that WWF and the above eight research institutes started the project in 2018. The purpose is to provide a systematic and objective report on the health diagnosis of the Yangtze River, provide policy advice for strengthening the ecological environment protection of the Yangtze River basin and implementing the green development strategy of the Yangtze River Economic Belt, provide policy suggestions for the protection and management of the Yangtze River ecosystem, and stimulate and promote different stakeholders to actively participate in the Yangtze River protection.
Kyle Rambotti, Global Director-General of WWF, said in the preface that as the first complete basin-level index in the world, the Yangtze River Vitality Index is also an innovation, and its concept connotation and evaluation method are expected to be further promoted worldwide. After all, for the major rivers in the world, we can’t reverse the trend of freshwater ecosystem loss and biodiversity decline until we better understand their vitality.
As the core of the report, Kyle Rambotti said that a complete basin-level index in the world is the Yangtze River vitality index, which sorts out many indicators and selects representative, indicative, concise, traceable and sustainable indicators to comprehensively reflect the health status of the Yangtze River freshwater ecosystem from three dimensions: hydrology, water environment and water ecology. The main conclusion of the index evaluation is that the overall health status of the Yangtze River is B-, and it shows regional differences with human activities.
The Paper, as the strategic cooperation media of the project, sent reporters to interview the relevant experts of the research group on the hydrology, water environment and water ecology of the Yangtze River before the report was released, so as to comprehensively interpret the report on the vitality of the Yangtze River.
Hydrological article
Hydrological index should be considered comprehensively.
The report points out that as an important characteristic of freshwater ecosystem, the change of hydrological situation determines the water quality, habitat and biological life history process of rivers. At the same time, the amount of river sediment transport and the change of sediment erosion and deposition significantly affect the biogeochemical cycle, water quality, river-lake relationship and the development of estuary delta, which is of great significance to the function of river ecosystem. The indexes for evaluating hydrological situation in the report mainly include hydrological process indicators and connectivity indicators.
Jin Chen, the leader of the research group of the report and a professor at the School of Water Resources and Hydropower of Wuhan University, told The Paper that the hydrological index is mainly aimed at natural rivers, that is, compared with the era without large reservoirs (before 1980), the higher the index, the closer it is to the natural hydrological process.
He said that at present, the main stream and tributaries of the upper reaches of the Yangtze River (except Chishui River) are not pure natural rivers. Therefore, the hydrological index is not high, which is mainly aimed at natural ecosystems such as fish. For densely populated China, it is necessary to build a reservoir. It cannot be simply said that a high hydrological index is better, and a low hydrological index is not good. "Both human beings and nature need water resources. The high or low hydrological index reflects the difference between human beings and nature in water resources distribution. It is necessary to comprehensively consider the needs of human development and nature protection and make rational distribution and regulation."
Global warming and the development of urban agglomeration affect the hydrological situation.
Besides being influenced by the connectivity between reservoirs and rivers and lakes, climate change also shapes the hydrological situation of the Yangtze River, which is mainly reflected in precipitation and flood events. Li Xin, a member of the research group and a doctor from the National University of Singapore, told The Paper that the report analyzed the impacts of ENSO (El Nio-Southern Oscillation, El Ni? o/La Ni? a and Southern Oscillation) events and global warming on the extreme precipitation index and hydrological core index by correlation analysis.
The results show that ENSO events have a significant impact on the extreme precipitation indexes in the source, upper and middle reaches of the Yangtze River basin. Specifically, La Nina events in ENSO events will generally increase the intensity and frequency of extreme precipitation in the source, upper and middle reaches of the Yangtze River basin, which may lead to an increase in flood risk in the Yangtze River basin. Global warming has a significant impact on the index of extreme precipitation in the middle and lower reaches of the Yangtze River basin, which will generally increase the intensity and frequency of annual precipitation and extreme precipitation events in the middle and lower reaches of the Yangtze River, and may also increase the flood risk in the Yangtze River basin.
Li Xin also stressed that the impacts of global warming and ENSO events on hydrological core indexes in different water resources areas show spatial differences, which indicates that hydrological processes have complex responses to global climate change. He believes that "this requires us to further strengthen the impact assessment of climate change on the regional hydrological cycle process, and constantly improve the ability of the Yangtze River basin to scientifically respond to climate change under the background of" Great Protection of the Yangtze River ".
According to the analysis of the report, the rapid development of urban agglomerations in the middle reaches may lead to frequent floods and an increase in the average flow during the flood season. In this regard, Li Xin explained that "the urbanization process has turned many permeable surfaces into impermeable surfaces, resulting in reduced infiltration, increased surface runoff components and increased peak urban flood discharge".
Nature-based solutions may ease the flood control situation in the Yangtze River.
According to the above analysis of the two experts, it can be seen that climate change, land use and other factors all affect the hydrological situation of the Yangtze River, making the flood control situation in the Yangtze River basin more complicated. This summer, the middle reaches of the Yangtze River once again experienced the test of a big flood. How to alleviate the complicated and severe situation, the report proposes that the solution based on nature should be one of the important means in the future when necessary engineering measures are adopted. Jiang Luguang, one of the technical leaders of the research group and an associate researcher at the Institute of Geographical Sciences and Resources, Chinese Academy of Sciences, explained this scheme in detail.
The World Conservation Union (IUCN) defines "nature-based solution" (NBS) as "an action to efficiently and adaptively respond to social challenges and bring benefits to human welfare and biodiversity through the protection, sustainable management and restoration of natural or artificial ecosystems". Jiang Luguang believes that this is completely consistent with China’s ecological civilization concept of respecting nature, adapting to nature and protecting nature. He told The Paper that there are many concrete manifestations of nature-based solutions, such as ecological restoration, adaptive strategies of ecosystems, and green infrastructure.
Taking the flood situation of Poyang Lake in flood season this year as an example, Jiang Luguang introduced the function of "returning farmland to lake" project to adapt to the natural rhythm of the Yangtze River and promote the harmony between people and water. In the flood season of 2020, some hydrological stations in Poyang Lake experienced the highest flood level in history, and the project of returning farmland to Poyang Lake fully played the role of flood storage and detention for the first time. Returning farmland to lake dikes can store about 2 billion cubic meters of flood water, reducing the water level of the lake by 25-30 cm in flood season, and greatly alleviating the flood control pressure of key dikes (protecting towns or tens of thousands of acres of fertile land).
In addition, the ongoing sponge city construction is also a good "nature-based solution". Sponge city advocates giving priority to the use of natural drainage system and low-impact development facilities in urban development and construction to realize natural accumulation, natural infiltration, natural purification and sustainable water circulation of rainwater, which can not only make full use of the natural restoration ability of water ecosystem, but also be an important means to solve the problem of urban waterlogging. For the Yangtze River basin, sponge city can reduce the adverse effects of drastic changes in the underlying surface of the basin on the runoff and runoff.
Water environment chapter
The water environment index in the middle and lower reaches of the Yangtze River is low.
Freshwater ecosystem is the main receiving place of nutrients and organic matter exported by terrestrial ecosystem. The quality of water environment determines whether freshwater ecosystem can provide clean water resources, and nutritional status plays an important role in shaping biological composition and community structure in freshwater ecosystem. The water environment index of the Yangtze River vitality index is mainly aimed at evaluating the main pollutant indexes.
The report pointed out that the main pollutants affecting the water environment index include industrial wastewater, domestic sewage and agricultural cultivation. When calculating the water environment index, the main basis is the water quality index.
Xu Yanxue of the Environmental Planning Institute of the Ministry of Ecology and Environment explained this. "We selected the water quality monitoring sections of major rivers and lakes in the Yangtze River Basin, and calculated three indicators representing water nutrition and organic pollutants, namely ammonia nitrogen, total phosphorus and permanganate index, and obtained the water environment index of each region (main river reach, main tributaries, four lakes, etc.) and evaluated it. The higher the water environment index, the lighter the water pollution and the better the water quality; The lower the water environment index, the higher the water pollution and the worse the water quality.
Xu Yanxue told The Paper that, after calculation, the overall water environment quality of the Yangtze River basin is at the national middle-upper level. However, from the main stream of the Yangtze River, the water environment index in the middle and lower reaches is relatively low, which is B-.
"The social and economic development in the middle and lower reaches of the Yangtze River is rapid, with concentrated industrial enterprises and active production activities. The typical pollutants discharged into the environment by these enterprises are total phosphorus, ammonia nitrogen and organic matter. The permanganate index reflects the concentration of organic matter in water. Although each enterprise has relevant emission standards to limit the amount of pollutants entering the environment, the total amount of emissions will be relatively high. At the same time, the amount of pollutants produced by agriculture and life and the amount of pollutants brought in by the upper reaches of the Yangtze River will be superimposed, resulting in total phosphorus, ammonia nitrogen and permanganate in the middle and lower reaches of the Yangtze River.
At present, the regulatory system can not accurately locate pollution sources.
According to the analysis of the report, the high concentration of pollutants will lead to the decrease of dissolved oxygen in the water body and affect the growth of aquatic organisms. At the same time, the high concentration of total phosphorus will affect the concentration of total phosphorus in the downstream lake water body, leading to the eutrophication of the lake. The Paper noted that the report made a separate analysis of the vitality indices of the four major lakes in the Yangtze River Basin, namely Poyang Lake, Dongting Lake, Taihu Lake and Chaohu Lake, among which the water environment of the four lakes was the key point.
Taking Taihu Lake as an example, the report explains the water environment crisis faced by the lake and its solutions. Since the cyanobacteria crisis in Taihu Lake in 2007, the state and local governments have done a lot of work on pollutant emission reduction and lake pollution control, and achieved remarkable results, but they still failed to return to the concentration level of nutrient elements in the 1970s and 1980s. Under unfavorable meteorological conditions such as high fever and southeast wind, cyanobacteria still broke out in Taihu Lake in recent years, which still failed to change the nature of algal lakes.
The Paper interviewed Yang Hongwei, deputy chief engineer of Suzhou Institute of Environmental Innovation in Tsinghua, about why Taihu Lake has not achieved remarkable results so far. He first affirmed the governance direction of eutrophic lakes. He believes that from the international experience of lake eutrophication control, the management of eutrophic lakes is a long-term project, and the time scale of 10 years is not enough to fundamentally change the essence of lake eutrophication. Judging from the current measures and effects of water pollution control in Taihu Lake, we have achieved remarkable results, especially the concentration of total phosphorus and total nitrogen has decreased significantly, and the frequency and severity of cyanobacteria outbreaks have also decreased significantly, so there is no deviation in our control direction.
However, he also admitted that although there is no deviation in the direction of governance, the regulatory system still needs to develop towards precision. "The current monitoring system can’t meet the requirements of smaller-scale grid supervision, can’t accurately locate pollution sources, and it is difficult to achieve accurate pollution control. This is also a new requirement for the regulatory system in the next step of precise lake governance."
We should continue to pay attention to the types and toxicity of emerging pollutants in water.
The Paper noted that the report specifically mentioned the emerging pollutants in the Yangtze River. Yang Hongwei told The Paper that emerging pollutants generally refer to substances that have not been related to environmental management policies, regulations or emission control standards, but may be included in the control object according to the assessment of their detection frequency and potential health risks. These substances are not necessarily new chemicals, but usually pollutants that have been in the environment for a long time, but have been discovered in the near future because of their low concentration, their existence and potential harm and the development of detection technology.
At present, emerging pollutants detected in the water environment mainly include endocrine disruptors, drugs, personal care products and other trace organic pollutants. Usually, the detection concentration in the water environment is at the level of ng/L. At this concentration level, it generally does not have acute toxicity, and it mainly produces chronic toxicity to organisms in the Yangtze River and further to human body, which is not enough to achieve long-term toxic concentration. However, it has potential endocrine disrupting properties, teratogenesis, carcinogenesis, mutation and resistance gene changes and other chronic toxicity, so we should continue to pay attention to the types, concentrations, sources, migration and transformation, toxicity of emerging pollutants in water, so as to grasp the hazards of emerging pollutants in water in time and provide reference for the formulation of corresponding environmental management policies and regulations.
Water ecology article
The middle reaches of the Yangtze River are frequently disturbed by various human activities, and the water ecology is the worst.
The water ecological index mainly evaluates the richness, diversity, community structure and habitat of aquatic organisms in the main stream of the Yangtze River and four lakes (Dongting Lake, Poyang Lake, Chaohu Lake and Taihu Lake). Water ecology is a "living" part of vitality, and its index directly reflects whether the Yangtze River still has vitality and how much vitality it has.
Chen Yushun, the technical director of the evaluation of the water ecological status of the main stream of the Yangtze River, a researcher and doctoral supervisor at the Institute of Hydrobiology, Chinese Academy of Sciences, said that the water ecology of the main stream of the Yangtze River is generally at the B- level. That is to say, on the whole, the water ecology of the Yangtze River has been at an unhealthy level, which shows that the Yangtze River is really ill. Among them, the water ecological index in the middle reaches is the worst.
It is embodied in the decrease of fish species, natural fishery catch and early fish resources. Chen Yushun said, "The number of fish species in the middle reaches of the Yangtze River has decreased by 36 from 97 in the past, the number of endemic fish species has decreased by 16 from 38 in the past, the number of threatened fish species has decreased by 11 from 16, the number of finless porpoises has decreased from 902 in the past to 193 now, the natural fishery catch has decreased from more than 400,000 tons in the past to 80,000 tons now, and the early fish resources have decreased from 6.7 billion in the past to 9 now.
Chen Yushun further explained this. "Due to the hydropower development in the upper reaches of the Yangtze River and its tributaries, and the interference of human activities such as fishing, shipping, sand mining and industrial and agricultural development in the middle reaches of the Yangtze River, the middle reaches are greatly affected by the superposition. Such as the change of hydrological situation, the decrease of sediment, the utilization of beaches, the reproduction of aquatic organisms such as fish, the degradation and loss of key habitats for growth, and the serious lack of bait resources. Coupled with the direct and indirect effects of overfishing, the above indicators in the middle reaches of the Yangtze River are very low, which in turn affects the comprehensive index of water ecology in the middle reaches of the Yangtze River.
In order to ensure the effect of fishing ban, ecological monitoring should be strengthened
According to Chen Yushun’s description, the biological resources of the Yangtze River are declining and the biodiversity is declining, so it is urgent to "ban fishing in the Yangtze River for ten years". In order to effectively alleviate this crisis, the state has issued a series of relevant documents and notices to make arrangements for a total ban on fishing.
On July 15, 2020, Yu Kangzhen, Vice Minister of Agriculture and Rural Affairs of China, said at the policy briefing held by the State Council Office that on January 1 this year, 332 aquatic life reserves in the Yangtze River Basin had been completely banned on schedule, and the fishing ban in key waters in the Yangtze River Basin would be implemented for 10 years from January 1, 2021.
For the 10-year cycle, Chen Yushun explained to The Paper that 10 years is a relative value, and fish can complete a certain breeding cycle, which should also be a tentative period. During this period, most aquatic organisms can have a relatively long period of proliferation and population recovery. However, in these 10 years, it is also necessary to adjust other stress factors, carry out habitat restoration and restore biological resources at the same time.
In order to effectively monitor the effect of the ban on fishing, Chen Yushun suggested that the relevant departments should open up a green channel for scientific investigation when carrying out a comprehensive ban on fishing, so as to ensure the availability of scientific research vessels and the simplicity of handling fish fishing licenses. In this way, scientists and fishery resource managers can really work in the same direction to jointly promote the ecological protection of the Yangtze River.
The ecology of the four lakes in the Yangtze River is not optimistic as a whole.
According to the report, Dongting Lake, Poyang Lake, Chaohu Lake and Taihu Lake are the four largest freshwater lakes in the Yangtze River Basin, among which Dongting Lake and Poyang Lake directly connect with the Yangtze River. These four shallow-water and fresh-water lakes play a huge ecosystem service function in terms of water regulation, material supply, providing biological habitat, maintaining biodiversity and keeping clean water sources, and play an extremely important role in protecting the water ecological health of the Yangtze River basin and maintaining the vitality of the Yangtze River.
Junfeng Gao, the technical director of the ecological assessment of Sihu Lake, a researcher and doctoral supervisor of Nanjing Institute of Geography and Lakes, Chinese Academy of Sciences, told The Paper that according to the assessment results, the current water ecological indexes of Dongting Lake and Poyang Lake are B-, Taihu Lake is C- and Chaohu Lake is D. That is, the water ecological health of Dongting Lake and Poyang Lake is in an upper-middle state, Taihu Lake is in an upper-middle state, and Chaohu Lake is in a lower-middle state. On the whole, the water ecological state of the four lakes is not optimistic, and the problems in Taihu Lake and Chaohu Lake are particularly serious.
Poyang Lake should be put in the first place in the differential treatment of the four lakes
As for how to harness the ecology of the Four Lakes, Junfeng Gao thinks that the protection and harness countermeasures are different because of the great differences in the natural geographical conditions, the influence degree of human activities and the water ecological problems faced by the Four Lakes.
He pointed out that the Dongting Lake basin should maintain the river-lake connectivity and the original hydrological rhythm of Tongjiang Lake, control the amount of pollutants entering the lake in the basin, strengthen the collection and treatment of urban domestic sewage, and control the agricultural non-point source pollution discharge. Poyang Lake basin should pay attention to the protection of biological species population and diversity, strengthen the protection of its habitat, and strictly supervise and manage nature reserves.
For Taihu Lake and Chaohu Lake, where the problem is particularly serious, it is also necessary to treat them differently. Junfeng Gao said that the Taihu Lake Basin should strengthen pollutant discharge control, control the total phosphorus flux into the lake, and strengthen the prevention and control of cyanobacteria bloom in the lake water. Chaohu Lake Basin should control the pollution of Nanfeihe River, Shiwuli River and Paihe River, strengthen the construction of urban environmental infrastructure in Hefei, improve the sewage collection rate and strengthen the level of nitrogen and phosphorus removal. Strengthen the prevention and control of cyanobacteria bloom in the lake area and establish a monitoring and early warning mechanism for cyanobacteria bloom in Chaohu Lake.
Among the four lakes, Junfeng Gao particularly emphasized the management of Poyang Lake. He said that Poyang Lake is the largest of the four lakes and is closely related to the main stream of the Yangtze River. Poyang Lake has rich ecosystem types, huge ecosystem service capacity, rich habitat types and biodiversity, and unique hydrological rhythm, which provides rich food and good food availability for various migratory birds. Its water ecological health quality has the most obvious effect on enhancing the vitality of the Yangtze River, so it is also the most important lake among the four lakes. The protection and restoration of Poyang Lake water ecology should be placed in the first place of the four lakes.
