Restoring, Remaking and Greening Freshwater Ecosystems: A Review of Projects in China

Recent projects in China affected by the State Council’s 2015 Water Pollution Prevention and Control Action Plan (China Environment News 2015) have aimed at mitigating water pollution and improving water quality. These projects examined ways of cleansing water bodies by artificially adjusting the proportion and structure of microorganisms, plants and animals in an effort to restore and stabilize a freshwater ecosystem. This attempt to reconstitute healthy biological systems informs ecological restoration, particularly freshwater ecosystems.

Since the 2015 Water Pollution and Control Action Plan and efforts to comprehensively improve China’s physical environment, a number of diverse projects on a range of scales have been implemented, including the restoration of an artificial lake covering 13,000 square meters, the construction of a 6,700-square-meter wetland, and the restoration of a 10-kilometer-long river (Cheng et al. 2021). This paper summarizes challenges, main goals, strategies, and techniques of landscape water ecological restoration in China using the restoration practices of lakes and rivers as examples.

Main Challenges of Restoring Freshwater Environments

Decades of rapid urbanization in China have caused tremendous environmental impairment with pollution (visual and physical) of the nation’s freshwater ecosystems (Cheng et al. 2021). Numerous studies have verified this damage was caused by nonpoint and point source pollution from urban stormwater, industrial wastewater, domestic sewage, and runoff from farmlands consisting of pesticides and animal waste—all discharging into slow-flow freshwater bodies in parks, reservoirs, estuaries, and bays (Davis et al. 2010, Zheng and Wang 2009). Aquatic organisms, especially algae, propagate extensively and negatively transform the ecological balance of these water bodies (Maguire 1963). In 2015, Dianshan Lake and related rivers in Shanghai collectively were a polluted exemplar of eutrophication (Figure 1). They were partially covered with oil pollution, domestic waste and duckweed, and were visually dark with low transparency. One river was silted-up and water flows were slow. Impacted by the artificially hard embankment (Figure 2), the diversity of animals and plants decreased annually. As a result, this local freshwater ecosystem became fragmented, and its natural self-purification capacity was lost.

According to China’s environmental quality standards for surface water (GB3838-2002) ( Ministry of the Environment of the People’s Republic of China n.d.), the water quality of rivers around Dianshan Lake was found to be inferior and heavily polluted water body in 2015 based on field samples. The main pollution indexes are represented in Figure 3.

Figure 1.

Eutrophication and siltation of rivers around Dianshan Lake, Shanghai (2015).

Figure 2.

Artificial embankments of Dianshan Lake and its surrounding rivers: steel concrete structure (left), masonry stone (middle) and gravel (right) (2015).

Figure 3.

Content of main pollutants in rivers around Dianshan Lake, Shanghai, in summer and winter (2015).

The main pollution sources affecting Dianshan Lake and its surrounding rivers were waterfront proximity of numerous agricultural lands, including croplands, aqua-farms, nurseries and orchards, as well as a small number of industrial lands. Because these rivers were generally static with limited discharge and the hydraulic change time was long, they lost the capacity for self-purification and therefore pollutants and sediments increased. Furthermore, the lakefront edges were artificially hardened, hindering the exchange of natural materials and energy between the freshwater and the adjacent environment.

Figure 4.

Main solutions for restoration and construction of a landscape water ecosystem.

Main Objectives for Restoring Freshwater Landscapes

The primary objectives of water restoration projects in China are: 1) Protecting and repairing the water body, 2) Preventing water pollution and related deterioration of water quality, 3) Protecting aquatic life and its biodiversity and natural ecosystems, and 4) Restoring damaged aquatic ecosystems which curb the trend of degradation. In essence, protective measures involve restoration and promoting repair. This mitigates pollution and fosters protection.

The broad goals for the ecological restoration and construction of freshwater landscapes...