IV. PROTECTION OF REGIONAL NATURAL ENVIRONMENT
B. Flood prevention and water resources protection in the Tai LakeThe Tai Lake is embedded in the Yangtze Delta, like a bright pearl. Its excellent geographical location and rich climatic resources make it world-famous for fish and rice. For several centuries past its silk and silk-based ecological agriculture was acclaimed worldwide as the acme of perfection. Its prosperity has been the foundation of national safety and the wealth of the people for the past thousands of years. The urbanization of Shanghai depends heavily on the development and advance of the Tai Lake watershed. The early orange and Biluo tea in the Xidongting Hill to the east of the Tai Lake is a typical suburban agriculture identified with Shanghai city. The silk handicraft industry in Zhenze was the cradle of the light textile industry of Shanghai in modern times. However, the almost limitless production force created by the Industrial Revolution caused people to ignore and even defy ecological agriculture, which is the accord formed between our forefathers and nature, in the relentless pursuit of money and wealth. The ecological environment has now become so fragile. The water in the Tai Lake was polluted and the floods of the Tai Lake threatened the whole watershed, especially Shanghai in its lower reaches. In July 1990, in the Tai Lake, eutrophication manifested itself in an outbreak of algae. The lake surface was covered by vicious yellow and green plankton and algae, 0.5 m thick and with a putrid smell. The water production of the Meiyuan main-water factory in Wuxi City decreased from 200,000 to 50,000 tons (even to nothing during a particularly serious period). Forty-six enterprises had to stop production and the direct economic loss amounted to 130 million yuan. Thus the protection of fresh water in the Tai Lake is vital for the protection of Shanghai and the whole Yangtze Delta.
The Tai Lake watershed is near the Yangtze River mouth to the north, Hangzhou Bay to the south, and East Sea to the east. The Mao Mountains, Jieling and Tianmu Mountains form the western boundary between the Tai Lake watersheds and the watersheds of the Qinhuai River, Shuiyang River and Qiantang River. Its area is 36,500 sq km. Until late 1990, it had 1,500,000 mu of cultivated 1and and a population of 33,546,200, respectively accounting for 1.58 per cent and 3.36 per cent of the whole country. Its total industrial and agricultural output value was 1,098.3 billion yuan which accounted for 11.58 per cent of total country. Therefore, its economy is very advanced and its economic density is very high. -
The watershed land formation is mainly plain and its relief is low and flat. The sea level of most of the area is below 5 m, and even 2-4 m in Hang-Jia-Hu areas, while the lowest is the Tai Lake and the lake group around it, at only 2 m above sea level. Its rainwater is abundant; river network cross and lakes are scattered like stars in the sky. Its water surface area accounts for 17 per cent of the total watershed area. So once floods occur, the economic loss is likely to be very large. The Tai Lake Watershed Management Bureau takes flood prevention and waterlogged drainage as its main duty, being mindful of the comprehensive benefits of water supply, water transportation and environmental protection at the same time. Then the overall-planning programme of comprehensive harnessing of the Tai Lake watershed was enacted in 1985. However, the extremely large floods in the Tai Lake (the lake water level broke the record by reaching 4.79 m) caused the economic loss of 13 billion yuan in 1991. Since 1991, the construction of water conservation facilities in the Tai Lake has been carried out rigorously. -
The flood prevention projects were designed with an occurrence frequency of once in fifty years, which mainly solves the outlet of floods in the Tai Lake. Ten key projects for harnessing the Tai Lake were planned on the premise that the Tai Lake could regulate and store half of the floodwater in the watershed every year and the remaining floodwaters could directly drain into the Yangtze River though the Wangyu River and the Taipu River-Huangpu River respectively. These projects required an investment of 7 billion yuan and will have been finished by the year 2000.
(a) Ten key projects
Four of these ten key projects are major watershed projects and are the first flood prevention projects in China to be subsidized by the International Development Bank and the International Development Association. Three of them are regional flood prevention projects and the other three are inter-provincial boundary projects. Construction of the first seven projects has advanced substantially during the Eighth Five Plan period, and the programme and feasibility reports of the remaining three projects have been planned according to a tight and concerted schedule. The total accumulative investment of 2.1 billion is complete, and the pattern of flood prevention and waterlogged drainage in the Tai Lake watershed has been set.
This project is 57.14 km long and links one of the main sluiceways for the Tai Lake floods, which begins from Shijia Port in Hengshan Town near the Tai Lake to the west, links the Mao River to the east and flows into the Huangpu River through the Xietang Pool. At present, the sluiceway has been completely linked and some of the works have been finished, checked, accepted, -and put in use.
The project begins from Shadunkou at the Tai Lake to the south and flows into the Yangtze River through Genjinkou in Changshu City, and the entire length is 60.8 km. It is one of the main sluiceways of the Tai Lake in the rainy season, and it can draw and store water from the Yangtze River to the lake in drought years.
To improve the storage capacity of the Tai Lake for floods, a 269.6 km-large embankment around the Tai Lake is being raised and reinforced. 108 sluices around the lake, and 126 buildings and flood prevention projects in Changxing Plain are being built. The earthworks have been finished along the whole line and the construction of protection slopes and dikes is being actively advanced.
This project carries floods and waterlogged water from the Hang-Jia-Hu area through the four sluices (Changshan, Nantaitou, Yanguanxia and Shangtang) and drain it into the Huangzhou Bay along the Koumen Works at Hangzhou Bay. Three outlets to the sea have been completed and put in use.
To widen and dredge river courses and reinforce dikes along the rivers in order to carry floodwater from the mountainous regions in western Zhejiang Province and drain it into the Tai Lake.
To widen and dredge regional river courses, and set up pumping stations on the Yangtze River to drain regional floods and waterlogged water to the Yangtze River and the Tai Lake (such as the Wei village water control key project).
To widen and dredge regional river courses, repair and build river control sluices and pumping stations which carry the water from this region and the areas to the west of the Tai Lake into the Yangtze River (such as the Baiqugang water control key project).
It is 26 km long and the it is the main river course for carrying the floods and waterlogged water of depressed areas in northern Jiaxing to the eastern Huangpu River.
To widen and dredge river courses, and enlarge the drainage capacity of the Dingmaozheng projects.
To widen and dredge river courses, and improve the boundary sluices and gates between Zhejiang Province and Suxi which drain floods and waterlogged water from the northern depressed areas in Hang-Jia-Hu to the Pu River.
Figure 60. The ten key projects in the Tai Lake area
This system is an information network for watershed flood control which makes use of the watershed hydrological auto-measurement and reporting system and the postal and telecommunication public data interchange network. The network centre is located in the Shanghai Bureau, and also includes seven branch centres (respectively located in Suzhou, Wuxi, Changzhou, Zhenjiang, Huzhou, Jiaxing, and Qingpu in Shanghai) and some relay stations. Every branch centre, considering regional hydrological characteristics and the demand of operation and stage of water conservancy works, arranges and designs tele-metering stations which auto--measure and report the data for four critical items (rainfall, water stage, wind direction and power). The data collected by the tele-metering stations can be transmitted to the branch centres at any time, and then in turn to the bureau centre by the branch centres. There is a total of 76 designed tele--metering stations in the whole watershed. The installation of equipment has been already finished and is now in the debugging process. When the system is eventually finished, the bureau centre will be able to collect all data of the water regime in the whole watershed every fifteen minutes. The introduction of this auto-measurement and monitoring system of the water regime in the Tai Lake is a firm and positive step in following the strategy of “water conservancy on the basis of science and technology".
(c) The protection of water resources in the Tai Lake
The pollution of the Tai Lake is caused by the normal pollution sources, such as industry, agriculture, human life, manufacturing and transportation. The development of town and township enterprises has presented a more apparent menace to the water quality of the Tai Lake in recent decades. The popular use of pesticides and chemical fertilizers is also an important pollution source. The discharge of sewage reaches 3.5 billion tons every year (including Shanghai) which accounts for about one-tenth of the total sewage discharge in China. Its water body pollution is a kind of organic pollution. COD and NH3-N are the main pollutants and heavy metals and poisonous materials are of minor importance. The content of nutrient elements such as N and P in its water body is a little high and two-thirds of its water surface is in a eutrophicated state. In recent years, there has been algae spraying several times on its northern bank, which has already seriously restricted the development of a healthy regional economy. Therefore, the committee for the protection of water resources in the Tai Lake watershed compiled and published an annual assessment of the quality of water resources in the Tai Lake watershed for eight consecutive years. They drafted "The management regulations of water resources protection of the Tai Lake watershed", and finished the preparation for establishing a water environment monitoring centre for the Tai Lake watershed. The bureau also carried out international cooperation work with the Netherlands recently and engaged in the research of water quality of the Tai Lake watershed river network system. They established a management and decision-making support system of watershed water quality and put the hydrodynamic model of the river and lake system in the Tai Lake watershed and the one-dimensional water quality model of Delivag into the geographical information system. As a result, they can predict and stimulate the water regime and water quality at any time and at any water body section in the watershed. The system will be a powerful and scientific support for the management and decision-making mechanism for the watershed.
The Tai Lake is regarded as one of the key points of water pollution treatment in the Ninth Five Year Plan period. The Committee of Environmental Protection of the State Council held a special spot inspection meeting of the execution of the environmental protection laws in the Tai Lake watershed in Wuxi City in April 1996. Attendees at this meeting reached a common agreement on the harnessing urgency of the Tai Lake, the necessity of adopting appropriate measures and the goals that will hopefully be realized. The decisions were: -
This "Water Purification Project" will set out to ensure that the average water quality in the whole lake will reach the standards of national one-class water by 2010. The processing rate of sewage in cities and towns in the planned areas along the lake will reach 90 per cent while the disposal of human sewerage in the rural areas will reach 30 per cent. In order to achieve this, Jiangsu Province will harness or shut 241 pollution sources along the lake before the deadline of 1998. 43 sewage treatment factories in cities and towns will be built. The treatment capacity of human sewage will reach 885,000 tons. Demonstration areas of good agricultural ecology will be established in all continental region of one-class conservation zones around the lake. Now, in Suzhou City more than 100 enterprises that previously caused serious pollution have already been closed down. Four sewage treatment plants have been newly built.
Of course, not only the problem of water pollution but also the natural environmental protection in the Tai Lake watershed including flood prevention and waterlogged drainage, demands that we deal with the relationship between the economy and the environment correctly on the basis of the idea of sustainable development. It should be recognized that environmental protection and economic development are not contradictory like fire and water. On the contrary, they can and should be complementary. In fact, the flood prevention planning of the Tai Lake watershed had been finished before 1985, but not enough importance or attention was given to its implementation. There was no clear recognition of the function of environmental protection in economic development until the floods in 1991, which caused huge damage and serious loss of 13 billion yuan. The Tai Lake watershed was assaulted twice by rainstorms, in 1993 and 1995, and the highest water level of the Tai Lake reached 4.51 m and 4.32 m, which had been listed as the third and sixth highest water levels respectively since record-keeping began. Since 1991, the construction of water conservation projects has been carried out on a great scale. The enlargement and dredging of the Taipu River and the Wangyu River, has opened up an outlet for floods in the Tai Lake and created advantageous conditions for watershed flood prevention and waterlogged drainage. The construction of the great dikes and dams around the lake has improved the flood storage capacity of the Tai Lake and protected the safety of 20,000 sq km areas. The southern drainage projects caused the flood water level drop 0.17-0.23 m in Hang-Jia-Hu areas, reducing the stricken area of 20,000-27,000 ha, and lightening the waterlogged condition of 180,000 ha of farmland in the depressed areas of Hang-Jia-Hu region. The construction of water conservation facilities in the Tai Lake watershed has reduced the direct economic loss of 5.7 billion yuan from the disasters up until 1995. It has played a vital and pivotal role in protecting the economic development of the whole watershed.
China is a developing country, and development should be its undeviating
policy. However, this does not mean that environmental protection can be
ignored or even treated lightly. The experience and lessons learned from
the flood prevention construction and protection of water resources in
the Tai Lake watershed has effectively proved that economic development
is the material base of environmental protection and environmental protection
can promote economic development. It is only in the process of their mutual
and harmonious promotion that a truly sustainable environmental ideal can
be attained - firmly, effectively and gradually.