Comprehensive Application of Safety Assessment —— Water Resources Safety Assessment in Xiamen City

Water is the basic element of human existence. The security of water resources in a region is directly related to the social stability and people's health in the region. Ensuring the safety of regional water resources and drinking water is an important content to realize the goal of building a well-off society in an all-round way and building a harmonious socialist society, and it is also an urgent task to truly implement people-oriented

Regional water resources safety evaluation is the premise and basis for people to understand the water resources situation in this region and take effective measures to ensure the safety of drinking water. Water resources security can be evaluated from three aspects: water resources quantity, water resources quality and water resources development and utilization. The quantitative evaluation of water resources is based on the evaluation of surface water and groundwater resources, mainly by analyzing the relationship between precipitation, surface water and groundwater, and then adding surface water resources and groundwater resources, deducting repeated calculations; The quality evaluation of water resources is mainly aimed at the pollution situation of water resources; The evaluation content of water resources development and utilization includes the present situation of water supply infrastructure, water supply situation, water supply efficiency and comprehensive evaluation of water resources.

General situation of water system and reservoirs in Xiamen

The water systems in Xiamen are all short rivers in mountainous areas, which originated in this area. The basin area is small, the flow is short, the slope is large, and the water quantity changes greatly with the seasons. The island's surface water system is underdeveloped, mostly short-flowing, which flows radially out of the sea. Some water systems outside the island are relatively developed. The main rivers are Dongxixi, Jiuxi, Guanxun and Houxi, with a total drainage area of 939.25 km2, accounting for 69% of the city's total land area. Only the areas of Tongan Xixi and Jimei Houxi River basins exceed 100 km2, and the areas of Jiuxi and Guanxun River basins are 50 ~ 100 km2.

There are 5 medium-sized reservoirs and 3 small reservoirs 103 in the city, with a total storage capacity of 2430 1 10,000 m3 in 2004. Medium-sized reservoirs include: Dou Shi Reservoir, Tingxi Reservoir, Dong Xi Reservoir, Zhuba Reservoir and Xinglinwan Reservoir; The main small reservoirs are Xitou Reservoir, Keng Reservoir, Bantou Reservoir, Zengxi Reservoir, Hubin Reservoir, Xiaoping Reservoir, Hexi Reservoir and Shizhai Reservoir.

The Jiulong River is also a river of special significance to Xiamen's water supply. Jiulong River is the second largest river in Fujian Province, and its main stream consists of Beixi, Xixi and Nanxi. Beixi, the main stream of Xiamen Jiulong River, originates from Meihua Mountain in Longyan City, passes through xinluo district and zhangping city in Longyan City, flows into Huaan County, Changtai County, Zhexi and Jinlong in Zhangzhou City, and then flows into Zhangzhou Plain. Fuhe River joins Xixi River in Longhai City.

Quantitative evaluation of water resources in Xiamen city

1, water resources in Xiamen

Xiamen is located in the south subtropical monsoon climate zone and belongs to the subtropical maritime climate. The average annual precipitation is 65,438+0,533.3 mm, which is equivalent to the total annual precipitation of 2.406 billion cubic meters. Precipitation and runoff vary greatly in time and space, and are unevenly distributed among years. During the flood season (April ~ 10), precipitation accounts for 80% of the whole year, runoff accounts for more than 85%, and the annual precipitation is 3.2 times that of the smallest year. The distribution of precipitation gradually decreases from northwest to southeast. The annual precipitation in the northwest mountainous area is more than 2000mm, and the annual precipitation in the coastal area and Xiamen Island is about1100 mm.

The local average surface water resources in Xiamen for many years are11.800 million m3, the groundwater resources are 1.36 million m3, and the repeated calculation is 0.81.300 million m3, and the average total water resources for many years are 1.235 million m3. According to the statistics of registered population, the per capita water resources in Xiamen is only 87 1 m3, which is about 40% of the national average and 25% of the Fujian average. If the temporary population is considered, the per capita water resource is 576 m3, which is a serious water shortage area.

In 2004, the annual precipitation in Jiulong River Basin was 1325.3mm, which was equivalent to the total precipitation195.36 million m3, and the surface water resource was 7.805 billion m3, which was equivalent to the runoff depth of 529.5 mm. In that year, Xiamen diverted water from Jiangbei Creek in Jiulong River1970,000 m3.

2. Number of drinking water sources in Xiamen

The drinking water sources in Xiamen mainly include Beixi Water Diversion, Dou Shi-Bantou Reservoir and Tingxi Reservoir (the function of Shangli Reservoir has been adjusted to landscape water). The standby water sources include Hubin Reservoir and Xinglinwan Reservoir. Among them, Beixi water diversion is the main water supply source in Xiamen, accounting for nearly 80% of the total water intake. See the table below for the supply of drinking water sources in various water source protection areas.

Present situation evaluation of water resources quality in Xiamen city

1. Water quality of main rivers in Xiamen

According to the water resources bulletin of Xiamen in 2004, the water quality of major rivers in Xiamen has been polluted to varying degrees, including:

(1) Tongan Xixi is the largest river in Xiamen, including Lotus Stream, Aoxi, Tingxi, Dongxi and other tributaries. The water quality of the control section of Wuxianqiao in the control reach of Dongxi River is worse than Grade V, and the water pollution is serious, with the river length accounting for 34.438+0% of the tributary of Dongxi River. The water quality of the control section of Qikeng Bridge at the confluence of Aoxi and Lianhuaxi is Grade IV, and the water body is slightly polluted, with the river length accounting for 44.3% of Xixi water system. The water quality of the control section of Xinxi Bridge in the main stream of Xixi River is Grade V, and the water body is heavily polluted. The river length accounts for 2 1.4% of Xixi River system. The water quality of the control section of Shuangxi Bridge in Xixi control reach is worse than Grade V, and the water pollution is serious, accounting for 1 1.3% of the total length of Xixi water system. The main items exceeding the standard are total phosphorus, dissolved oxygen, five-day biochemical oxygen demand and ammonia nitrogen, which belong to organic pollution.

(2) Jimei Houxi is the second largest river in this city, and its upstream includes Zhuxi and Xu Xi tributaries. The water quality of the controlled reach of Houxi River is Grade V, and the water body has been seriously polluted, with the river length accounting for 22.6% of the water system. The main items exceeding the standard are total phosphorus, permanganate index, five-day biochemical oxygen demand and ammonia nitrogen, which belong to organic pollution.

(3) The water body in the controlled reach of Jiuxi River is polluted by organic pollutants, the water quality is Grade V, and the river length accounts for 67.7% of the water system. The main items exceeding the standard are total phosphorus and five-day biochemical oxygen demand.

(4) The water quality of Guanxun River is Grade V, and the water body is polluted by organic pollutants, and the river length accounts for 58.0% of the water system. The main items exceeding the standard are total phosphorus, ammonia nitrogen, permanganate index and five-day biochemical oxygen demand.

2. General situation of drinking water quality in Xiamen.

According to the monitoring results of the municipal environmental monitoring station in 2005, the water quality of all reservoirs in the city failed to fully meet the requirements of environmental functional zones, which was caused by non-point source pollution such as urban sewage around the polluted main reservoirs, domestic sewage of urban residents, sewage from rural livestock breeding and surface runoff formed by exposed soil in reservoir catchments.

(1) Beixi Water Diversion Beixi Water Diversion is a specially protected water area, and Class II water quality standard in GB3838- 2002 Environmental Quality Standard for Surface Water (hereinafter the same as the standards for Bantou-Dou Shi Reservoir, Tingxi Reservoir and Shangli Reservoir) is implemented. In 2005, the water quality of Beixi water diversion basically reached Class II water quality standard, and the items exceeding the standard included total phosphorus, permanganate index and dissolved oxygen. The water quality compliance rate is 50.0%. Compared with the same period in 2004, the over-standard projects are basically the same, and the water quality compliance rate has increased. There are still excessive water diversion projects in Beixi River, mainly because with the economic development, many industrial parks or residential quarters have appeared in the middle and upper reaches of Jiulong River, but the number of industrial parks and residential quarters along the coast has increased, which has failed to control and treat industrial wastewater, domestic wastewater and aquaculture wastewater brought by a large number of developed livestock and poultry breeding in time and effectively.

(2) Bantou-Dou Shi Reservoir In 2005, the water quality of Bantou-Dou Shi Reservoir basically reached Class II water quality standard, and the water quality compliance rate was 965,438 0.67%. Except the average concentration of total phosphorus and total nitrogen exceeded the standard, all other projects met the second-class water quality standard, and the water quality was better than that in 2004. The main reason for improving the water quality of Bantou-Dou Shi Reservoir is to strengthen the control of agricultural non-point source pollution in the reservoir area, especially the management of livestock and poultry breeding in the reservoir area.

(3) Tingxi Reservoir In 2005, Tingxi Reservoir basically reached Class II water quality standard, with a water quality compliance rate of 75.0%; The main items exceeding the standard are permanganate index, total phosphorus and total nitrogen. Compared with 2004, the water quality has obviously deteriorated. The main reason is that the livestock breeding in the upper reaches of the reservoir can not be effectively stopped, and the breeding sewage is directly discharged into the reservoir without any treatment, resulting in water pollution and eutrophication.

(4) Lakeside Reservoir In 2005, the water quality of Lakeside Reservoir met Class IV water quality standards, and the water quality compliance rate of functional areas was zero. The main pollution items are total nitrogen, total phosphorus and five-day biochemical oxygen demand; Compared with 2004, the water quality has improved. The main reason for improving the water quality of Hubin Reservoir is the comprehensive improvement of Hubin Reservoir, and it is planned to shut down all livestock and poultry farms and key pollution sources in the reserve.

(5) Xinglinwan Reservoir In 2005, the water quality of Xinglinwan Reservoir only met the Class V water quality standard, and the water quality compliance rate of functional area was 8.33%; The main pollution items are total nitrogen, total phosphorus and five-day biochemical oxygen demand. Compared with 2004, the water quality compliance rate increased slightly.

Evaluation on the present situation of water resources development and utilization in Xiamen

1. Status of water supply infrastructure

The main water supply projects in Xiamen include Bantou Dou Shi Reservoir, Tingxi Reservoir Group, Xiangxi River Diversion Project, Small Surface Water Supply Project and Beixi Diversion Project. Beixi Water Diversion Project is the main water supply project in Xiamen, and Bantou Dou Shi Reservoir is an important supplementary water supply source in Xiamen. Tingxi Reservoir Group and its related water supply projects are of great significance to the urban and agricultural water supply in Tong 'an and Xiang 'an.

2. Present situation of water supply and use

According to the water resources bulletin of Xiamen in 2004, the total water supply in Xiamen in 2003 was 608 million m3 (excluding seawater supply), the surface water supply was 565.438+0.3 million m3, and the groundwater supply was 87 million m3. The local water supply accounts for 67.6% of the total water supply, and the inter-basin water transfer is 65.438+0.97 billion m3, accounting for 32.4% of the total water supply. The overall level of water resources development and utilization is medium, and the development and utilization rate of water resources in the city is 30.4%, of which the development and utilization rate of surface water resources is 36.3% and the exploitation rate of groundwater resources is 42.6%. The development and utilization of groundwater is on the high side, exceeding the warning line, which needs attention. In 2004, agriculture, domestic water and industrial water accounted for 44.9%, 25.6% and 29.7% of the total water consumption respectively.

3. Water supply and water use efficiency

Per capita comprehensive water consumption quota, water consumption per 10,000 yuan GDP and farmland irrigation quota not only comprehensively reflect a city's water consumption level, water saving level and water resources management level, but also are closely related to economic development level and scientific and technological progress, and their values reflect the reasonable degree of water resources development and utilization. Generally speaking, compared with Fujian Province and other coastal cities, Xiamen's indicators are at a relative level (as shown in the following figure), especially the water consumption per 10,000 yuan of industrial output value and per 10,000 yuan of GDP, which is far lower than that of Shanghai, Fuzhou, Zhangzhou, Sanming, Putian, Dalian, Ningbo, Qingdao and Shenzhen.

4. Analysis of water resources supply and demand

Nanjing hydraulic research institute made a systematic analysis and study on the balance between supply and demand of water resources in Xiamen, and predicted the water demand of the whole city and its administrative regions. When the guarantee rate of irrigation water reaches 95%, by 20 10, the total water demand of the whole city will be 899410 million m3. According to the current water supply conditions, that is, the diversion flow of Beixi in Xiamen is 14m3/ s, Dou Shi and Tingxi reservoirs are operated according to the current dispatching mode, and the water supply of other small water conservancy projects in all districts of the city is 2. The amount of sewage treatment and seawater reuse is 44.5 million m3, and the subsystems of Tongan and Xiamen Island will be short of water in different degrees, especially in dry years. In 2020, the city's total water demand will be11320,000 m3. If the water diversion from Beixi River is maintained at the scale of 14 m3/ s, Dou Shi Reservoir will be used for storage and replenishment, and the water supply of other small water conservancy projects will be maintained at 2 10/00000 m3. Even if urban sewage treatment and reuse and seawater utilization increase to 76 million m3, the gap between supply and demand will be relatively large.

Countermeasures to ensure water resources and drinking water safety in Xiamen

1 to ensure the balance between supply and demand of water resources.

According to the above-mentioned quantitative evaluation of water resources in Xiamen and the analysis of the present situation of water resources development and utilization, although the per capita comprehensive water consumption quota, water consumption per 10,000 yuan GDP and farmland irrigation quota in Xiamen are at a relative level compared with those in Fujian Province and other coastal cities, Xiamen is a region with a serious shortage of water resources, and water resources are still the main resource bottleneck for Xiamen's development.

To ensure the safety of water supply in Xiamen, we need to ensure the quantity of water resources first. According to nanjing hydraulic research institute's research on the supply and demand of water resources in Xiamen, in 20 10, when the diversion flow of Beixi reaches 14 m3/ s, Dou Shi Reservoir will be used to regulate and store the diversion, and Lianhua Reservoir will be built at the same time, so as to balance the supply and demand of water resources in Xiamen. For example, Beixi River Diversion 1.4m 3/s, and Dou Shi Reservoir is used for storage and replenishment. In the non-dry season, the diversion flow of Beixi River will be increased according to the actual water demand, and the water resources in the city can reach the balance between supply and demand. In 2020, if the discharge of Beixi River is increased to 20 m3/ s, the balance between supply and demand can be maintained only if Youshi Reservoir operates in the mode of "storage, recharge and diversion". Therefore, in the near future, under the condition of not changing the Xiamen-Zhangzhou water transfer agreement, we should make full use of the diversion capacity of Beixi Water Diversion Project, increase the diversion flow of Beixi Water Diversion Project according to the actual water demand in the non-dry season, and change the operation mode of Bantou Reservoir in Dou Shi to "storage and replenishment". On this basis, it is considered that the Beixi water supply system will supply water to Tong 'an and Xiang 'an through networking, and the water supply scale will be 250,000 ~ 300,000 m3/d. During this period, the first phase of Longyinxi Yang Fang Hub project should be ready to be put into operation around 20 10. In the medium and long term, on the basis of the above, strengthen the networking water supply capacity of Xiamen subsystem and Tongan subsystem, increase the water supply scale to 400,000 ~ 500,000 m3/d, actively prepare for the second phase project of Yang Fang around 2065,438+05, and consider the construction of Lianhua Reservoir according to the supply and demand of water resources. In each planning period, we should actively adjust the industrial structure, save water, improve the utilization rate of seawater, rainwater and sewage, reduce dependence on external water sources and reduce the risk of water supply.

2. Ensure the quality of water resources, especially drinking water sources.

Judging from the current water quality in Xiamen, the situation is not optimistic. Most water systems in cities cannot meet the requirements of functional areas. Although the current drinking water sources can basically meet the requirements of drinking water quality, some indicators still exceed the standard. Therefore, the water quality safety in Xiamen needs to be guaranteed from the following aspects.

(1) Continue to carry out comprehensive river basin improvement to improve river water quality.

In order to effectively control the water pollution of the East and West Rivers, the municipal government started the comprehensive improvement of the water pollution of the East and West Rivers in early 2005, and proposed to achieve the goal of "clean water, green shore and beautiful scenery" in three years. Over the past year, various departments have carried out remediation of industrial, livestock and poultry breeding, urban domestic sewage and other pollution sources, as well as river dredging and revetment remediation, and achieved good results in comprehensive management: industrial wastewater basically meets the standard or has zero discharge; All livestock and poultry farms in the prohibited areas along the stream were demolished and closed, and other livestock and poultry farms achieved zero ecological emissions; Some urban domestic sewage has been brought into the sewage treatment plant for treatment; The landscape on both sides of the strait has gradually improved, and the ecological environment of Dongxixi has improved significantly. At present, except for total phosphorus, total ammonia and fecal Escherichia coli, other indicators basically meet the requirements of Class III water quality standard in GB3838- 2002 Environmental Quality Standard for Surface Water. The next step is to strengthen the comprehensive law enforcement of enterprises along the river, enhance the awareness of mass participation and active cooperation, promote the development of various work, and form a long-term mechanism for river basin management. At the same time, the comprehensive improvement of river basin pollution can be further extended to other river basins to fully protect the ecological environment of rivers and the ecological security of water resources.

(2) Further promote comprehensive pollution control in Jiulong River Basin.

With the social and economic development of Jiulong River Basin, the pollution of life, industry and agriculture entering Jiulong River is increasing day by day, and the water quality of Jiulong River is deteriorating sharply. This situation has attracted great attention of governments at all levels. 1999 the provincial government proposed to carry out comprehensive remediation of pollution and ecological damage in the Jiulong river basin, and cities such as Xiamen, Zhangzhou and Longyan carried out remediation actions. After three or four years' efforts, the regulation has achieved remarkable results, and the water quality of all sections along the Yangtze River has been greatly improved. However, the water quality has been declining since 2003. The main reason is the rapid development of livestock and poultry breeding and the growth of coastal population, which leads to the sharp increase of aquaculture wastewater and domestic sewage entering Jiulong River, and the nitrogen and phosphorus in the water quality seriously exceed the standard, which affects the water quality of Beixi Water Diversion Project in Xiamen. In order to ensure the quality of water diversion from the North Xijiang River, Xiamen needs to strengthen communication and coordination among the three cities in the Jiulong River Basin. On the basis of Xiamen-Quanzhou-Zhangzhou Alliance and "Mountain-Sea Cooperation" with Longyan, Xiamen will further promote the cities in the Jiulong River Basin to actively carry out comprehensive pollution control of the Jiulong River and complete the annual remediation tasks set by the province in time through ecological compensation mechanisms such as pollution control fund subsidies. Our city should also continue to improve the construction of urban environmental protection infrastructure, further reduce the total discharge of pollutants, actively promote the comprehensive improvement of the marine environment, promote the pollution control of livestock and poultry breeding, and extend Xiamen's experience in ecological breeding and fermentation breeding to the upper reaches of the Jiulong River to reduce the pollution discharge of aquaculture in the basin.

(3) Strengthen the protection of drinking water sources to ensure the safety of drinking water sources.

By delimiting the water source protection zones of Beixi Water Diversion, Bantou Reservoir in Dou Shi, Tingxi Reservoir and Shangli Reservoir, the water quality and quantity of the surface water source of domestic drinking water in Xiamen are protected, and the vegetation and natural environment of the catchment area are protected. At present, the plan for the delineation of drinking water source protection areas in Xiamen has been approved by the provincial government. At the same time, in 2005, the renovation of Beixi water diversion project and the comprehensive improvement of water source protection areas of Bantou Reservoir and Tingxi Reservoir in Dou Shi were completed. Vigorously promote biogas digesters and fermented farming for livestock and poultry farmers in Tingxi reservoir area; Implement comprehensive improvement of lakeside reservoir, complete tap water renovation project, first-phase water supply and diversion project of Juan branch canal, and closure project of Caitang section of reservoir, and invest funds to lay sewage pipes in surrounding villages. Strengthen the supervision and investigation of industrial pollution sources that may affect the safety of reservoir water sources.

On the basis of ensuring the safety of existing drinking water sources, actively carry out the investigation of the second water source. The relevant departments of Xiamen have started this work, went to Changtai County of Zhangzhou City to investigate the ecological environment of the second water source, and discussed with Changtai County on further strengthening cooperation, which laid a good working foundation for * * * to do a good job in the ecological environment protection of the second water source.

Note: 1: domestic water and comprehensive water quota unit is L/d, farmland irrigation quota unit is m3/ mu, and water consumption per 10,000 yuan GDP and industrial output value is m3/ 10,000 yuan.