To commemorate the 28^th World Water Day and the 33^rd China Water Week, China Water Resources journalist made an exclusive interview with ZHANG Jianyun, Academician of the Chinese Academy of Engineering. The interview was themed on "Prioritizing Water Saving and Building Rivers and Lakes for Human Well-being".

Journalist: The theme of 2020 World Water Day is “Water and Climate Change”. Could you talk about climate change and its impacts, especially the impacts on China's water security? And how should we respond to those?

ZHANG: The theme of 2020 World Water Day is "Water and Climate Change". Its focus is on managing climate and water resources in a more coordinated and sustainable way since they are key inseparable factors in global goals such as sustainable development, climate change, and disaster risk reduction. Needless to say, water is one of the most precious commodities in the 21^st Century. Climate change is an indisputable scientific fact that has a big impact on natural systems like water resources system.

Although arguments exist in the academic community about climate change, general consensus has been reached on surface temperature and sea level rise and extreme events increase. According to China's Third National Assessment Report on Climate Change, over the past 100 years (since 1901), the surface temperature in China has increased by 0.9 to 1.5℃. The increase over the past 60 years is 1.38℃ with an average of 0.23℃/10a, higher than the global level. According to the Fifth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC), even if respective country tries to reduce greenhouse gas emission, temperature will continue to rise for a long period of time. It is a hot topic discussed in the international academic community whether the common goal of containing temperature increase within 2℃ by the end of this century will be achieved. Since the 1980s, in China, there has been no obvious change in annual mean precipitation, yet the distribution varies significantly. Particularly, precipitation in the Haihe River Basin, the Liaohe River Basin, and the Shandong Peninsula has reduced by about 10%. In the context of global climate change, China's sea level has shown a wavelike rising trend over the past 30 years. Since 1980, it has risen by an average of 3.2 mm/a, higher than the global average of 2.6 mm/a.

The Wuliangsuhai Lake in Inner Mongolia

Climate change has brought great risks and challenges to China's water security.

First, water shortage in northern China is becoming more prominent. On the one hand, the comparative analysis of the hydrological series before and after 1980 shows that the measured river runoff in northern China is generally decreasing. In the cases of the Haihe and Liaohe river basins, the runoff has decreased by 35% to 80%. According to the results of the Second National Water Resources Survey and Evaluation, the surface water resources in the Haihe, Liaohe, Yellow and Huaihe river basins has decreased by 47.2%, 13.4%, 15.4% and 11%, respectively. On the other hand, as temperature rises, the water consumption of agriculture, industry, life and ecology will increase to varying degrees. Therefore, climate change has further exacerbated the water shortage in northern China.

Second, global warming will accelerate water cycle. The rise in atmospheric temperature and water holding capacity will add instability to atmosphere, thus leading to extreme weather with frequent local heavy rainfall. Urban heat island effect generated by urbanization has also made urban rainstorms and flooding more and more prominent.

Third, sea level rise has brought about many problems. It will weaken the defense capacity of flood control and storm surge prevention projects, bringing risks to coastal areas. The rise will also impact the ecosystem of costal and estuary areas, increasing the scope of saltwater, estuary salinity and seawater erosion on groundwater along coastal regions. In addition, it will threaten the security of fresh water resources in coastal areas where the method of avoiding saltwater and storing freshwater is adopted. Therefore, the climate change impacts on China's water security are multifaceted, systematic, significant and complex.

Climate change requires a scientific response.

First, we need to slow down this change. According to the IPCC assessment report, the concentration increase of greenhouse gases generated by human activities has led to the rise in surface temperature. Many countries regard greenhouse gas emissions control as a long-term measure to mitigate climate change. Chinese Government, for example, thinks that energy conservation and emission reduction is an important and effective means and breakthrough to optimize economic structure, promote green, cyclic and low-carbon development, and accelerate ecological progress. The Comprehensive Plan for Energy Conservation and Emission Reduction During the 13th Five-Year Plan Period has been formulated, a series of policies issued, and actions taken. To build a conservation-oriented society, we could start with petty things with everyone’s participation.

Second, we should improve our ability to adapt to change. In terms of water security, we need to strengthen demand-side management, accelerate the construction of water-saving society, and reduce the rigid demand for water resources. Other measures include improving system carrying capacity, establishing a national water network with cross-basin water transfer as a basic framework, and optimizing the allocation of water resources to deal with the uneven spacial distribution of water resources; tackling the uneven temporal distribution of water resources through engineering projects; strengthening the use of unconventional water resources and risk control to improve the supply capacity through seawater desalination, waste water utilization, floodwater resources use, and low-quality water treatment. In terms of flood prevention and disaster reduction, it is necessary to enhance non-engineering measures. We could have more scientific decision-making by using multi-scale, full-factor information monitoring and early warning system. We could also boost disaster reducing capacity through efficient emergency management and social administration on floods. Engineering measures are also very important. We should comprehensively evaluate engineering projects and make sure they meet related defense standards in a changing environment. In terms of ecological environment, we must stick to green development and ecological priority.

Seawall in Xiamen City

Journalist: Chinese President XI Jinping attaches great importance on basin ecological protection. When in Chongqing and Wuhan, he put forward the requirement of "Together we protect the Yangtze River and stop major development", and in Zhengzhou, he called on ecological protection and high-quality development, and making the Yellow River the one for human well-being. Please talk about your understanding on these requirements.

ZHANG: President XI’s thought is based on the long-term plan of the great rejuvenation and sustainable development of the Chinese nation. He explained the importance of ecological protection in the Yangtze River Basin and the Yellow River Basin, and made clear the targets of high-quality development and ecological protection. High in level and rich in content, President XI's speeches pointed out the direction and set the tone for the governance and protection of the Yangtze River and the Yellow River in the new era. After studying the President’s speeches carefully, I obtained the following profound understandings.

First, President XI’s speeches on the Yangtze River and the Yellow River have set the requirements for all water-related work, and we should fully study their rich connotations. Due to different geographical, climatic and social conditions, each basin has its own features and problems. Global climate change and economic and social development have brought new water security issues and challenges to each river basin. Protection and restoration are crucial to the basins of the Yangtze River and the Yellow River, and to other basins as well. The hope of “Letting the Yellow River become a river for human well-being” is a hope for every river.

Second, water, the basis of ecology, is the most active controlling factor in ecosystem, and a decisive element of different ecological patterns such as forest, wetland, grassland, and desert. Water is also the core medium of material and energy transfer in a biological chain. Water supports photosynthesis, and energy and material conversion in terrestrial ecosystems, and it is also the most basic element of wetland bio-systems. The regulation and protection of water resources are necessary and important measures for the protection and restoration of water ecosystems. Therefore, we should scientifically determine basin ecological flow, and increase its guarantee rate.

Third, ecological protection is important for basin water security, while river basin management is complex and systematic, which has to be problem-oriented with comprehensive consideration and treatment. In the President’s speech, he emphasized the importance of flood control, and pointed out that flood was still the greatest risk in a river basin. He also noted the importance of water security, and said water should be regarded as the most rigid constraint on which cities, cultivated lands, population and production all relied. Targeting at ecological and environmental issues, he put forward the guideline of focusing on protection and governance, and objectives and measures of ecological protection and restoration. Insufficient water security capacity is the root cause of basin ecological and environmental problems.

Fourth, ecological protection and restoration of river basins require not only advanced science and technology, but also concept innovation of river basin development and management.

The Majinxi River in Zhejiang Province (photo by Liu Bailiang)

Journalist: Could you please talk about the demands for science and technology in basin ecological protection, and give some advice?

ZHANG: We can make efforts from the following aspects.

First, we need to strengthen basic theoretical research on, for example, mechanism and driving factors of basin ecological degradation, coupling effect of land surface hydrological processes and ecological processes, cause analysis of basin ecological degradation, evaluation theory of basin ecosystem service function, water-energy-food-ecology nexus, resource carrying capacity analysis, and analysis of system carrying capacity, vulnerability and resilience.

Second, we urgently need breakthroughs in key technologies. These technologies include protection and restoration technology of different basin ecosystems, ecosystem detection technology and instrument, ecosystem diagnostic analysis and early warning platform, system resilience improvement method and technology, and ecological effect mitigation and compensation technology for water-related projects.

Third, we need innovation in application and management. In regard to river basin ecological protection, we should make clear the protected objects and focuses, and the goals of protection and restoration. President XI emphasizes the protection and governance of river basins, so it is necessary to strengthen efforts in comprehensive governance and adaptive management, green development and governance model, ecological compensation mechanism and policy, cost-benefit analysis of ecological protection and restoration, etc.

As mentioned above, water is the basis of ecology, the indispensable material for basin ecological protection and restoration. Water ecological protection is an important component for water security in river basins. Therefore, in order to provide scientific and technological support for ecological protection and high-quality development of river basins, we should conduct research not only on basin ecological protection and restoration, but on water security, efficient use and protection of water resources, and other key areas.

Published in China Water Resources, No. 6, 2020.