On the morning of May 8, 2016, Prof. Wang Hao, an academician of Chinese Academy of Engineering (CAE) and expert in hydrology and water resources, was invited to the 70th SUSTech Academic Salon and delivered an inspiring lecture about the natural-social dualistic water cycle in river basin under constantly changing environment.

In the lecture, Prof. Wang, now the director of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, expounded the natural-social dualistic water cycle in river basin under changing environment from six aspects: the formation of natural-social dualistic water cycle theory, the main contents of dualistic water cycle theory, dualistic water cycle and integrated simulation of its associated process, methodology about the efficient regulation of water resources in river basin, multi-dimensional critical regulation of water cycle in Haihe River Basin and key measures for regulating its water security.

Human Activities: from Natural Water Cycle to Natural-Social Dualistic Water Cycle

Natural water cycle was the main pattern of water cycle on the earth, but the emission of green gas changes the dynamical system of water cycle; the transformation of underlying surface shape alters the parameter characteristics; massive usage and drainage of water results in the change of the structure of water cycle. Influenced by these human activities, the natural-social dualistic water cycle in river basin therefore comes into being.

Prof. Wang pointed out that natural water cycle consists of water collection and self-purification, including atmospheric process, earth surface process, soil process and subsurface process. Social water cycle comprises dissipation and pollution of water, including drawing, transporting, using, drainage, sewage treatment and reclamation and reuse of water. Driven by natural and social factors, the dynamic conditions, cycle structure and performance as well as parameters of water cycle evidently demonstrate natural- social dualistic characteristics.

Dualistic Water Cycle: Discipline Paradigm and Integrated Simulation

“Affected by human activities, basic processes of water cycle have undergone stable changes, transforming the consistency of hydrologic series. As a result, we put forward a discipline paradigm of dualistic water cycle, namely from the traditional restoration to separation-coupling.” Wang said. The two key issues of dualistic water cycle are the multi-process coupling interaction mechanism of natural-social water cycle and the water resources’ quantity-quality-effect transformation mechanism based on the whole process of water cycle.

Prof. Wang also introduced the main research contents on dualistic water cycle, including mutual effect and structural coupling of natural-social water cycle, multi-process and multi-scale time-space-coupling of dualistic water cycle, evolution rules of water cycle under constantly changing environment and dynamic evaluation of water resources as well as the prediction and regulation scheme of water cycle.

“Now detection of natural water cycle is comparatively satisfying, while observing networks of social water cycle remains relatively incomplete, resulting in unclosed observation networks of water balance. This situation has to be improved, because it exerts great negative influence on understanding the mutual effect and co-evolutionary mechanism of water cycle.” Prof. Wang added that observations in situ should be carried out in terms of the whole process, parameters and state variables of dualistic water cycle.

Model-building of Dualistic Water Cycle in Haihe River Basin 

Haihe River Basin in China is one of the places most strongly harassed by shortage of water and water problems, so studies on the evolution rules of water cycle in this basin are of great significance.

Using dualistic water cycle model, Prof. Wang together with his team simulated and predicted the past, current and future water cycle of Haihe River Basin, identified the evolution rules of the cycle and revealed the ecological evolution laws in the basin by analyzing net primary productivity of farmland and natural ecosystems, evapotranspiration, wetland area, etc.

“Different water-related issues can be boiled down to the inefficient use of water, so the key point of regulation is to transform inefficient water into efficient water. In addition, the inefficient water and efficient water are integrated concepts, which need to be valued by the economic, ecological and environmental integrated effects of water cycle.” Prof. Wang remarked. It can be concluded that the essential measures to regulate the water security in Haihe River Basin are to save water, use non-conventional water, build integrated water networks and strictly regulate groundwater.

Prof. Wang and his team built the integrated simulation and prediction of water cycle in river basin and its association process platform (NADUWA3E), which realized the comprehensive coupling simulation of three systems. What’s more, the scientific research project led by Prof. Wang The Evolution Rules of Water Cycle in River Basin and Efficient Use of Water Resources won the 2014 National First Prize for Progress in Science and Technology.

At the end of the lecture, Prof. Wang interacted with the audience and had discussions on such topics as the South-to-North Water Diversion Project.