Wetland Restoration

Dalian Lake wetland restoration zone is situated in the south of Lanlu Port, 3.5 km in the southwest of downstream zone of Dianshan Lake, Qingpu District, Shanghai City, with the total land of 14.6 km² and the core area of 4.6 km² (Fig. 1.1). There are nine natural villages of two towns, namely Jinze Town and Zhujiajiao Town in the wetland restoration zone, where the total population is 7,504 (2,650 households). Dalian Lake District is 58 km away from Shanghai People’s Square and Hu-Qing-Ping Highroad run through the zone to offer a convenient and quick transport (Fig. 1.2). Water from Dianshan Lake, getting through Xietang (Lanlu Port), converges with Yuanxiejing and Damao Port in Songjiang River, all three of them constitute Huangpu River; the Lanlu port runs through the whole region of Dalian Lake Zone. According to Regulations of Shanghai Municipality for Preservations on Upstream Water Sources of Huangpu River, the zone is an important water source protection zone of Shanghai Municipality, and its local ecological conditions have important strategic significance for Shanghai’s sustainable development.

As same as the forest, grassland, desert and ocean, the wetland is an important integral part of global ecological environment and an ecological system with particular hydrologic, soil and biological features. Generally the wetland refers to the natural transitional zone from water to land. The word of “wetland” was firstly mentioned by U.S. Fish and Wildlife Service in the publications titled by No. 39 Notice in 1956. In which the wetland was defined as the lowland covered by the intermittent or the permanent shallow water layer. Such definition satisfies with the needs of wetland administrators and wetland scientists finitely, and thence it is still adopted and used frequently by wetland scientists and wetland administrators nowadays. In 1979, Zoltai, in a discussion meeting of Canadian National Wetland Working Party, defined the wetland into the one as follows, i.e.: “the land, where the wet soil dominates and the aquatic plants grow, but the water level approaches to or exceeds mineral soil in the majority days in the unfrozen seasons”. The definition made by the Canadian for the word of “wetland” limits the hydrologic conditions and wet soil conditions more concretely. Upon years’ investigation, the wetland scientists of U.S. Fish and Wildlife Service defined the wetland as the one as follows, i.e.: “the wetland is a transitional zone of the terrestrial system and the aquatic system; on these lands, the water level is normally on or approaches to the earth’s surface, or is covered by the shallow water”.

For the Dalian Lake water system, where the Douji Port and the Dalian Port are connected with the Lanlu Port (Fig. 3.1), and the floodgate in the west side is the Lianhu floodgate, and the floodgate in the east is the Douji floodgate. The Lanlu Port in the north is the main connecting water course of Dianshan Lake and Huangpu River; the water flows from the west to the east and flows into the Huangpu River.

In recent almost 20 years, the Tai Lake watershed area has developed its economy rapidly and the township enterprises have been flourishing, but the wastewater treatment and governance level has been far behind than the increase of pollution discharge; plenty of wastewater were discharged into rivers, lakes and sea directly without treatment to cause all of them get serious pollution. Currently the industrial and domestic wastewater and sewage of 5,000,000,000 m³ are directly discharged into rivers and lakes in the Tai Lake watershed every year. Among which, the percentage of the wastewater treated is only 20 % or less. According to the monitoring on the cross-section of main rivers and lakes in the Tai Lake watershed in 2000, including the main lakes, for instance, Tai Lake, Dianshan Lake; the main water supply courses in the watershed, for instance, Taipu River, Wangyu River; the main watercourses connecting the Tai Lake, for instance, the East and West Shao River, Nan River, Zhihu Port, Liangxi River, Xujiang River; and the provincial boundary watercourses, for instance, Hongqi Pond, Shanghai Pond, etc., the water quality at the monitoring cross-sections of 19.4 % can reach the surface water standard of Grade II or III (evaluation standard: GB3838—88); the water quality at the rest monitoring cross-sections of 80.6 % is found polluted seriously; among which the water quality at the monitoring cross-section of 48 % is Grade IV, 14 % Grade V, but 23 % is inferior to Grade V (such water has no any use value). The pollution type of the rivers in Tai Lake watershed is the organic pollution, and the nonconforming index of water quality is the permanganate index (COD_Mn), ammonia–nitrogen (NH₃-N), etc. Since plenty of nutritive salts (nitrogen, phosphor and other pollutants) go into lakes, the lakes are entrophicated seriously. Currently the Tai Lake, the maximum water supply source area in the watershed, is entrophicated seriously. In view of the monitoring data 2000, 71 % water area was entrophicated, and 29 % was in the middle of eutrophication.

The whole functions of the ecological system of Dalian Lake wetland include the hydrologic regulation function, water quality purification function, substance production function and wetland tourism, etc. The main mechanism of the wetland system to control the non-point source pollution is to increase the runoff infiltration, delay runoff flow, increase dwelling time, etc., and then make pollutants detain in the system to decompose and transform, and finally reduce the pollutant loads from going into the downstream water body; meanwhile, the rainfall runoff intercepted shall be recycled, which can improve the utilization ratio of water sources and relieve the scarce water source. When designing the wetland system for controlling the non-point source pollution, it is needed to consider the characteristics of rainfall runoff (rainfall strength, rainfall duration, rainfall time interval, etc.), wetland dewatering time, drought tolerance of plants, transpiration and other factors so as to make the structure and functions of wetland fit to the randomness and rapid change of rainfall. The load of unit area affects the degradation efficiency of the wetland on pollutants; the improper design can make wetland system unworkable; in other words, the primary issue of the design work is to determine the pollution load of wetland area (currently it is needed to determine the pollutant reduction objective of wetland in accordance with the pollution source investigation result, and then obtain the pollution load of wetland area). In a wetland, the degradation extent of pollutant is related to its dwelling time; whereas the dwelling time is inversely proportional to the unit area’s load of wetland. The non-point source pollutant, retention rate of runoff and runoff process, dwelling time, water depth, etc. have close relation; however, the dwelling time of the runoff in the wetland system is controlled by the runoff inflow process.

The project is the first-stage project of Dalian Lake wetland restoration project (2,000 mu): Shanghai Dianshan Lake Wetland Restoration Demonstrative Project (in the west suburb of Shanghai); the total area of the project zone is about 420,000 m² (625 mu), including 60 % fishing ponds and 20 % forest lands, and 20 % lakes, roads and rivers. According to the different conditions of the area and the requirements of wetland restoration, the project area is divided into three functional subareas, i.e.: wetland restoration and reconstruction area (Subarea A), forest wetland cultivation area (Subarea B), shoal wetland restoration and biodiversity conservation area (Subarea C). The three subareas involve in different ecological functions and restoration focuses.

The project is Dianshan Lake Wetland Restoration Project Demonstration Zone in the western suburbs of Shanghai (625 mu), and is the Phase I project of the initial project of Dianshan Lake Wetland Restoration Project in the Western Suburbs of Shanghai. The project zone is located in Qingpu District of Shanghai, the Phase I project is located at the southeastern corner of the initial project of Dianshan Lake Wetland Restoration Project in the Western Suburbs of Shanghai, and takes up 625 mu totally.

The project is the Wetland Restoration and Reconstruction Area (Area A) of Shanghai Xijiao Dianshan Lake Wetland Restoration Model Area Project (625 mu), belonging to first stage construction model area, with total area 150 mu. The project is divided into three stages in implementation. The first stage project is terrain moulding and biodiversity improvement projects. Its main contents include accumulated water drainage, sludge digging, aeration, islands slope filling and construction, wetland bottom construction, etc. The second stage project is micro-topography wetland moulding and quick infiltration system project, mainly including the terrain transformation of deep water area, quick infiltration system construction, etc. The third stage project is the restoration system project of forests, shrub wetland and coast wetland, mainly including the vegetation plant of islands and shore slope belt, and the vegetation restoration of waters, etc.

The sampling and monitoring of the water quality and planktons of the wetland after the first stage model project of Dalian Lake were carried out between April 2010 and February 2011. Nine sampling places (No. 1–9) were set up in the whole project area, five (No. 10–14) were established at outside rivers before sludge was removed. Later, the sampling place No. 15 was added to Lanlu Port in accordance with the real condition. Sampling places are seen as Fig. 9.1.

The construction of the project has restored 60 kinds of aquatic plants and organisms of the wetland, such as arbors, shallow water emergent plants, deep water emergent plants, floating leaved plants, submerged plants, etc., which taking on the biodiversity of plant ecosystem after construction that changes with the characteristics of terrain. The wetland after restoration has been characterized with lush aquatic plants and organisms, plenty and limpid water, ecological stability and the stagger of all species that will not only produce biodiversity but also have good water-purifying effect all the year round.