West Lake is a small shallow lake with an area of 6.5 square kilometers, an average depth of 2.27 meters and a total storage capacity of120,000 cubic meters. With the development of economy and the growth of social population, from the late 1950s to the early 1980s, the eutrophication of the West Lake became more and more serious, and a large number of cyanobacteria grew and multiplied. 1958 and 198 1 year, cyanobacteria broke out twice, which reversed the normal succession of ecosystem and reduced the quality of water environment. Since the late 1970s, especially in recent years, the Hangzhou Municipal Party Committee and Municipal Government have regarded the comprehensive management of the West Lake waters as a long-term systematic project and an important task, adhered to the principle of "overall planning, comprehensive improvement, combination of governance and management, and management first", and adhered to the principles of people-oriented, minimum intervention, active protection, ecological priority and culture as the soul, and formulated and promulgated the Interim Measures for the Protection and Management of the West Lake Waters. At the same time, a series of major projects and control measures have been implemented one after another, which has improved the water quality of the West Lake as a whole and protected the ecological environment of the West Lake and its basin.

The first is to implement the pollution interception project around the lake to cut off the pollution sources that enter the lake from the periphery.

Pollution interception is the first step to control exogenous pollution in eutrophic lakes, and it is also the key strategy to cut off pollution sources from entering lakes. Before the implementation of the comprehensive treatment project of the West Lake, the domestic sewage of most units and residents in the area around the Lake was not intercepted and received, and a large amount of production and domestic sewage was directly discharged into the West Lake, which led to the serious exceeding of the ammonia nitrogen index and the serious decline of the water quality of the West Lake. Therefore, since the end of 1970s, Hangzhou has invested tens of millions of yuan to build a sewage interception pipeline around the lake 1 1.07 km and eight sewage pumping stations, so that 77% of the sewage along the lake is connected to the sewage pipeline. At 1979, 30 kilometers around the shoreline of the lake were stoned to prevent surface runoff from flowing into the lake and polluting the water quality; After that, the urban sewage reconstruction project around Shahe River was completed, and 10000 tons of domestic sewage was prevented from flowing back to West Lake every day. In recent years, the sewage interception and Lingyin drainage project of Beili Lake has been completed, which has formed a complete network of sewage interception pipelines in the whole West Lake basin. At the same time, more than 50 heavily polluting enterprises near the West Lake have been closed down and relocated, and a stricter examination and approval management system has been implemented for enterprises in this area. This effectively curbed the environmental pollutants around the West Lake from entering the lake, and better protected the environment of the West Lake and nearby residential areas.

Two, the implementation of the West Lake sediment dredging project, from the basis of removing nutrients accumulated for many years.

After the founding of New China, the West Lake was dredged three times on a large scale. The first dredging project, 1952, lasted for 8 years with a total investment of 4.54 million yuan. After dredging, the average depth of the West Lake is1.88m, and the water storage capacity is increased by 1.5 times. The second dredging started from 1976. 1999 12, the third dredging of the west lake sediment started, the largest in history, with a total investment of 235 million yuan. The project adopts the "environmental protection" dredging technology pioneered in China and adopts long-distance relay pipeline fully enclosed transportation. The whole project lasted for 4 years, with a dredging volume of 3.469 million cubic meters and a dredging area of 5.54 square kilometers. The average water depth of the West Lake has deepened from1.65m before dredging to 2.27m.. The implementation of dredging in the West Lake has cleared the upper silt about 60 cm from the bottom of the West Lake, effectively reduced the internal load of nutrients, weakened the eutrophication foundation of the West Lake, and significantly improved the water quality.

Third, implement the comprehensive improvement project of the upper reaches of the West Lake to further purify the water quality from the source.

According to the survey, before the treatment, the total annual discharge of four streams in the upper reaches of the West Lake reached about 2.56 million tons, which has become the main source of water pollution in the West Lake. For this reason, in recent years, the river regulation in the upper reaches of the West Lake in Hangzhou has focused on the treatment of septic tanks, garbage dumps, excessive sewage discharge and illegal buildings within 10 meters along the upper reaches of the river. So far, 186 units have been rectified within a time limit, 35 open septic tanks, 5 garbage bins and 5 public toilets on both sides of the stream have been cleaned, 7 public toilets have been built or demolished, 3 farms along the stream have been relocated, and the sewage from 46 units in the upper reaches has been incorporated into the municipal pipe network. The implementation of these measures has reduced the pollutants discharged into the West Lake to some extent. Among them, Changqiaoxi is the main treatment, and the polluted stream flows into the West Lake after being treated by sewage treatment equipment and restored by aquatic plants, reaching the Class III standard of surface water, so that the original sewage is everywhere and garbage is piled up, and an urban water ecological park integrating ecological, ornamental, leisure and scientific and educational functions is built.

Four, the implementation of the West Lake water diversion project, fundamentally ensure the improvement of water quality.

According to the fact that the upstream stream flow is decreasing year by year, in order to fundamentally improve the water quality of the West Lake and enhance its tourism value, it is decided to invest 1 1.69 million yuan to build the West Lake water diversion project. Qiantang River water will flow through Huangyushan Mountain and Jiuyan Mountain into West Lake through water pipes, and a water diversion project with a total length of 3 194.5 meters and a daily water intake of 300,000 cubic meters will be built. However, the Qiantang River water is affected by tides and upstream soil erosion, so it is difficult to guarantee the time and quality of water diversion from the West Lake. At the same time, due to the increased capacity of the West Lake after its westward advance, it is urgent to increase the water diversion capacity of the West Lake. Therefore, in 2002, while further increasing the water diversion, two new sedimentation tanks were built in Jiang and Chishanbu at the foot of the mountain. After treatment, 400,000 cubic meters of clean water is guaranteed to enter the West Lake every day. Since 2004, 65.438+0.2 billion cubic meters of water has been diverted from Qiantang River every year, which not only greatly improves the transparency of the West Lake, but also achieves the goal of completely replacing the fresh water of the West Lake once a month.

Five, the implementation of the comprehensive protection project of the West Lake, from the environmental quality to further enhance the taste of the West Lake.

The comprehensive protection project of West Lake (West Lake Westward Project) was started on June 5 +2, 2002. It is the largest project in the history of protection and development of the West Lake in the past thousand years, with a total investment of about 960 million yuan. The whole project lasted for three years.

According to the control plan of the comprehensive protection project of West Lake, on the one hand, some permanent residents and people who have changed from rural areas to non-rural areas in the scenic spot are evacuated, and the total number of existing buildings in the scenic spot is demolished and reduced. First, all the residents in the scenic spot and those who have completed the rural transfer before the village withdrawal have moved out *** 1685 people; Second, encourage farmers to move out through economic means, so that the permanent population of the scenic spot will be reduced to 36% before the implementation of the project, and the existing rural settlements will be properly gathered; The third is to build sewage collection and discharge systems for all rural concentrated residential areas and incorporate them into municipal sewage pipelines; Fourth, all the existing industrial enterprises in this area will be relocated; Fifth, hotels, restaurants and other "three-industry" enterprises with relatively independent location, difficult reception management and conducive to the allocation of tourism resources require their sewage to meet the standards themselves. This has a very positive effect on reducing the total amount of regional sewage pollutants, reducing the pollution load discharged into the West Lake and improving the water quality of the West Lake.

On the other hand, the highlight of the comprehensive protection project of the West Lake is the expansion of the West Lake to the west, with an additional area of nearly 90 hectares, which expands the area of the West Lake from the original 5.56 square kilometers to 6.5 square kilometers, and greatly increases the storage capacity of the West Lake. With the expansion of the West Lake, the number of upstream water distribution points has increased, providing sufficient water and good water quality for the West Lake, further expanding the living water area of the West Lake. At the same time, combined with biological measures such as planting suitable aquatic plants, the water quality of the West Lake will be further improved; And introduce the outlet of the lake into the river, so as to provide clean and sufficient water for the virtuous cycle of the urban water system, realize the purpose of "controlling water with water, using one water for multiple purposes and diverting three waters", and make Hangzhou a "three-water city" oriented by Qiantang River, West Lake and Canal.

The implementation of the comprehensive protection project of the West Lake has not only expanded the water environmental capacity of the West Lake, reduced the regional pollution load, expanded the space and regional landscape of the West Lake, improved and perfected the ecosystem function of the West Lake, promoted the development of Hangzhou's tourism economy with the overall improvement of environmental quality, and created better environmental and economic benefits; But also restored the original historical features of the West Lake, restored its authenticity and integrity, increased its cultural connotation, enhanced its own tourism charm and attraction to tourists, promoted the economic development of Hangzhou's tourism industry with rich natural and human landscapes, and achieved a "win-win" between social and economic development and environmental protection and ecological protection.

Six, the implementation of the West Lake research and exhibition project, to promote the sustainable development of the West Lake.

How was the West Lake formed, how was it protected in the past, what has been done in the protection and management in recent years, and how should it develop harmoniously in the future? Around these problems, the Hangzhou Municipal Party Committee and the Hangzhou Municipal Government have focused on two things: First, the West Lake Museum will be built, which will not only show the past lives of the West Lake, but also be equipped with activities that can be seen and participated, such as curtain movies, which will make education entertaining and attract many tourists. When the National Day was completed and opened last year, the seven-day holiday received 6.5438+0.28 million people, making it the most popular tourist spot in Hangzhou this year. The second is to set up the West Lake Research Institute to further strengthen the study of the past nature, humanities and history of the West Lake and decipher its "genetic genes"; At the same time, increase the research on the future development of the West Lake, grasp the inherent laws of its protection, management and operation, and promote the harmonious development of the West Lake.

The comprehensive protection project of Hangzhou West Lake came to a successful conclusion, and the panoramic view of "one lake, two towers, three islands and three dikes" returned to the world. The new pattern of "East is hot, West is prosperous, North is elegant, China and America" has basically taken shape, and the goal of returning the lake to the people has basically been realized. Generally speaking, the water quality of the West Lake has been gradually improving. According to the monitoring in the first half of 2005, the total nitrogen content in the water quality nutrition index of West Lake decreased by 3 1% compared with the same period in 2004, and the average transparency of water body reached 74 cm, which was nearly 20 cm higher than that of the previous year. At present, the natural ecology of the West Lake has been restored and its history and culture have been passed down. The West Lake has taken a big step towards the goal of "applying for the World Heritage".