Analysis of Water Problems in Beijing-Tianjin-Hebei Metropolitan Area
2.4. 1 water resources problems
The problem of water resources is mainly that the total amount of water resources is less, the per capita possession is reduced, and the supporting force of water resources is reduced. It has changed from general water shortage to comprehensive structural water shortage formed by the interaction of water shortage, water waste and water pollution.
Beijing-Tianjin-Hebei metropolitan area is a serious water shortage area, and the per capita water resource is only 3 17m3, which is only one seventh of the national average. The average amount of water resources per mu is 306 cubic meters, which is only one fifth of the national average. In order to alleviate the shortage of water resources, the utilization of foreign aid water and reclaimed water has been continuously improved (Table 2.6).
Beijing and its surrounding areas continue to suffer from drought. From 1999 to 2008, the annual average precipitation of 10 was 476mm, which was only 8 1% of the annual average precipitation. The average inflow of Miyun Reservoir and Guanting Reservoir, the main surface water sources in Beijing, was 286 million m3 and 88 million m3 respectively, and the storage capacity of the reservoirs decreased from 65.438+54 million m3 and 420 million m3 at the beginning of June 54, 2006 to 65.438+63 million m3 at the end of 2008 (Figure 2.7). The annual per capita water resource in Tianjin is 160m3, and when the Luanhe River is diverted into Tianjin, the per capita water resource is 370m3, which is far below the world water shortage warning line 1000m3. It is a serious water shortage area, which is a quarter of the national annual per capita water resources of 2338m3, lower than the national monthly average. The shortage of water resources has become a bottleneck restricting the development of Tianjin. Hebei Province is a serious resource-based water shortage province, with an average annual water resource of 20.3 billion m3 and a per capita water resource of 3 1 1 m3, which is one seventh of the national average, less than one third of the internationally recognized water shortage standard of per capita 1 10,000 m3, and even less than the Middle East and North Africa, which is famous for its drought and water shortage. In recent years, due to the rapid economic development and the continuous improvement of people's living standards, the water consumption in Hebei Province has increased year by year, and the annual water consumption has reached 22 billion m3, but the available amount is only 654.38+0.7 billion m3, and the contradiction between supply and demand is very prominent. According to statistics, the daily water shortage of cities in Hebei Province is 6.5438+0.5 million ~ 6.5438+0.7 million m3, and all cities are short of water to varying degrees. The average water resources in Shijiazhuang for many years is 2.24 billion m3. In recent years, the actual annual water consumption in Shijiazhuang has reached 3.5 billion to 4 billion m3, and the deficit is mainly made up by over-exploitation of groundwater. At the same time, due to the low level of water resources reuse, weak concept of water saving and serious waste, the contradiction between overpopulation and resource shortage has been aggravated. As long as the rivers and groundwater in the economic circle are seriously reduced (source: water resources research of Beijing-Tianjin-Hebei metropolitan area based on circular economy).
Fig. 2.7 Water inflow process diagram of Miyun and Guanting Reservoir 1999 to 2008.
2.4.2 Water environment problems
The water environment problem of Beijing-Tianjin-Hebei metropolitan area is that water pollution has not been effectively controlled and treated. In 2004 alone, the discharge of urban domestic and industrial wastewater reached 3 billion m3, including Beijing1.200 million m3, Tianjin 560 million m3 and eight cities in Hebei Province1. In 2004, the centralized sewage treatment capacity of 10 cities was only 4.53 million t/ d, and the annual sewage treatment capacity was only 654.38+49 million m3, which was less than half of the urban sewage discharge. Due to management and financial problems, many sewage treatment plants cannot operate normally.
River pollution is still serious. Of the 8,200 km river length evaluated by Beijing-Tianjin-Hebei metropolitan area in 2004, only 4,000 km river length meets the Class I-III standard of surface water environmental quality, and about 4,200 km is polluted to varying degrees, accounting for 53% of the polluted river length. Among them, Tianjin Jiyun Canal and North Canal, Zhangjiakou Yanghe River, Shijiazhuang Weihe River and Baoding Fuhe River are seriously polluted.
Most of the 25 large reservoirs have good water quality, but the water quality of Beijing Guanting and Chengde Miaogong reservoirs is worse than Class III, and the water quality of other reservoirs meets Class III standards. The water quality in Baiyangdian District is generally poor, with 56% of the water surface classified as Class IV, 22% as Class V and 22% as worse than Class V (Table 2. 13).
According to Environmental Quality Standard for Surface Water (GB3838-2002) and Environmental Quality Standard for Groundwater (GB/T 14848-93), the evaluation of surface water and groundwater shows that the water pollution in Beijing-Tianjin-Hebei metropolitan area is quite serious. In terms of surface water, the length of polluted rivers in Luanhe River and coastal areas of eastern Hebei accounted for 40.5% of the assessed river length, 63.7% in the north of Haihe River system and 77.5% in the south of Haihe River system.
As the water sources of the cities in the capital circle are mainly reservoir impoundment and groundwater, the evaluation results of reservoir and groundwater quality show that most of the 15 reservoirs currently evaluated are Grade III, Miyun, Daheiting and Gangnan reservoirs are Grade II, and Guanting and Yanghe reservoirs are the worst, which are Grade IV. The main items exceeding the standard are total phosphorus, permanganate index, coliform bacteria and dissolved oxygen.
Through the evaluation of shallow groundwater quality of 3 14 observation wells in the evaluation area of 6726 1km2, it is found that there is no Class I and Class II water quality, and the water areas of Class III, Class IV and Class V are 19372km2, 19255km2 and 28634km2 respectively. The main items exceeding the standard are ammonia nitrogen, total hardness and nitrite nitrogen. In the evaluation area, the groundwater quality in Chengde City is good. See table 2. 13 and table 2. 14 for the water quality evaluation results of main reservoirs and groundwater.
Table 2.13 Water quality of main water source reservoirs in Beijing-Tianjin-Hebei metropolitan area in 2004
Note: According to the Environmental Quality Standard for Surface Water (GB3838-83) implemented on June 6, 2002, according to the environmental functions and protection objectives of surface water areas, they are divided into five categories according to their functions:
Class I: mainly applicable to source water and national nature reserves;
Class II: It is mainly applicable to the first-class protected area of centralized drinking water surface water source, the habitat of rare aquatic organisms, spawning grounds for fish and shrimp, feeding grounds for larvae and juveniles, etc.
Class III: it is mainly suitable for centralized drinking water surface water sources, fish and shrimp wintering grounds, migration routes, aquaculture areas and secondary protected areas in other fishery waters and swimming areas;
Class Ⅳ: It is mainly suitable for general industrial water areas and recreational water areas where human body is not in direct contact;
Class ⅴ: Mainly applicable to agricultural water use areas and waters with general landscape requirements.
Table 2.14 Water Quality of Shallow Groundwater in Plain Area of Beijing-Tianjin-Hebei Metropolitan Area in 2004
Source: China Water Affairs Bureau, Special Report on Water Resources, 2004.
The water quality of more than half of the rivers in the city is not up to standard, and shallow groundwater in some plain areas is polluted. Within 520 kilometers of the Sixth Ring Road, some river sections are seriously polluted. Due to the lack of fresh water supply, the treated river water quality cannot be guaranteed. In 2008, the annual sewage discharge in Beijing was 65.438+0.32 billion m3, the total sewage treatment was 65.438+0.43 billion m3, and the sewage treatment rate was about 78.9%. There are still a lot of untreated waste water discharged into rivers and seepage pits. 48% of the rivers in the city are polluted to varying degrees, 46% of the rivers exceed the water quality standard of Class IV, and 45% of them exceed Class V. Most of the rivers in the lower reaches of the city seriously pollute the water bodies exceeding Class V.. A large amount of wastewater from the upstream of Guanting Reservoir is discharged into the reservoir, which leads to the reservoir water quality exceeding the Class III standard of surface water environment. After 1997, it can no longer be used as a drinking water source for urban life, and Miyun Reservoir has a trend of eutrophication in recent years. 47.5% of the groundwater exceeds the Class III standard, mainly for the total hardness, turbidity and NH3-N exceeding the standard.
If the primary natural water quality is not considered, only the water quality caused by secondary pollution is considered. The representative area of monitoring wells in the capital circle is 7255 1km2, of which 49% is unpolluted (Class III water quality), 24% is lightly polluted (Class IV water quality) and 27% is heavily polluted (Class V water quality). The main pollutants are ammonia nitrogen and nitrite nitrogen. Groundwater pollution in cities (Table 2. 15).
Table 2. 15 Groundwater pollution unit in cities and counties (including basins): km2
Source: Water Report of China Water Affairs Bureau, Beijing, 2004.
2.4.3 Water ecological problems
The water ecological problems in Beijing-Tianjin-Hebei metropolitan area are mainly manifested in three aspects: river interruption, wetland shrinkage and groundwater overexploitation. The main reasons are the decrease of water resources and the destruction of water environment.
2.4.3. 1 The river is cut off, and the amount of water flowing into the sea drops sharply.
Luanhe River, Douhe River, Jiyun River, Chaobai River, North Canal, Yongding River, Baigou River, South Juma River, Tanghe River, Zhulong River, Hutuo River, Fuyang River, Ziya River and other plain reaches, including below Yongding River, below Jiuwangzhuang of Jiyun Canal and Suiya River, more than half of the rivers have dried up. In 2004 (dry year), the inflow of Luanhe River, Chaobai River, Daqinghe River and Ziya River was only 654.38+000 million m3, which was more than 95% lower than the average in 1950s. The drying up of rivers makes aquatic animals and plants lose their living conditions, their functions of supplying groundwater, transporting sand and discharging salt, and their functions of navigation and landscape. Due to the decrease in the amount of water entering the sea, the living environment of aquatic organisms in major estuaries has deteriorated, and the siltation in estuaries has intensified, and the task of dredging is heavy every year.
Wetlands in 2.4.3.2 are shrinking and their functions are declining.
Baiyangdian, Qingdianwa, Huang Zhuang Wa, Qilihai, Dahuangbaowa, Tuanbowa, Beidagang, Dalangdian, Nandagang and other nine important lake wetlands in the plain, the area decreased from 2570km2 in 1950s to 469km2 in 2000, a decrease of 82%. The shrinking of wetlands has greatly reduced its functions as a "kidney of the earth" to regulate climate, store floods, purify water bodies, provide wildlife habitats and serve as a biological gene bank.
Overexploitation of groundwater in 2.4.3.3
Cities such as Tangshan, Shijiazhuang, Baoding and Langfang, which are dominated by plain groundwater, are forced to increase the amount of groundwater exploitation, and the shallow groundwater level drops at the rate of 1 ~ 2m every year. The proportion of groundwater exploitation is increasing, from 67% of total water supply in 2000 to 78% in 2004. Due to the decrease of recharge such as precipitation infiltration, the groundwater level continues to decline. Overexploitation of groundwater has exhausted aquifers in some areas. For a long time, due to the continuous drought and shortage of water resources, coupled with the weak awareness of water ecological protection, water and soil resources in some areas have been over-exploited, and the competition between human beings and natural water has become prominent, and the phenomenon of national economic water crowding out ecological environment water has become serious. Beijing overexploits about 580 million m3 of groundwater every year. Due to the over-exploitation and utilization of water resources, ecological water in rivers, lakes and groundwater systems has been squeezed out, resulting in a series of ecological and environmental problems such as river cut-off, lake shrinkage, wetland degradation, groundwater aquifer drainage, land desertification and so on. After more than ten years' efforts, the management of groundwater resources in Beijing has made some achievements, especially the serious over-exploitation phenomenon in Beijing urban area has been controlled, but at present, the development and utilization of groundwater resources in suburban counties still lack macro-control means.
2.4.4 Flood
Among natural disasters, floods, mudslides, droughts, typhoons and other water-related disasters account for more than 80%. The crisis of water resources will inevitably bring a series of problems such as the deterioration of ecosystem and the destruction of biodiversity, which seriously threatens the survival of mankind.
There are various types of urban water disasters, and there are basically five according to geographical location: ① Mountain side type: the city is built on the alluvial fan of the mountain pass or at the foot of the mountain, and heavy casualties are often caused by mudslides and landslides when there is heavy rainfall. (2) Riverside type: The city is close to the big river. Once the dike near the city breaks, the city will be besieged by floods. ③ Lakeside type: The city is located by the lake. When the water level of the lake rises in flood season, the low-lying areas of the city will be flooded. (4) Coastal type: The city is located on the seashore. Due to regional subsidence and other factors, waterlogging disasters are often very serious. ⑤ Depression type: Cities are built in low-lying areas or areas with difficult drainage, and urban drainage facilities are insufficient, resulting in serious waterlogging losses in cities, and some cities become disasters when rainfall is slightly high.
The Beijing-Tianjin-Hebei metropolitan area is the main urban area, and the water disaster problem first manifests itself in urban pavement hardening, street rainwater siltation, and rainwater infiltration in time, which causes waterlogging and affects the normal work and life of the city. Especially in recent years, Beijing's persistent drought has caused sandstorms to attack Beijing, causing the deterioration of urban air quality. The flood disaster in Beijing is mainly caused by the interruption of urban traffic and the damage of road subgrade by heavy rain, and some scenic spots around Beijing are facing the test of debris flow, such as Miyun, Huairou, Yanqing, Fangshan, Mentougou and Pinggu, which are all high-risk areas of debris flow. In addition, the lack of water resources, less precipitation, urban heat island effect is serious. Urban water disasters in Tianjin are mainly coastal, mainly waterlogging, and eight urban areas in Hebei are mainly depression-type water disasters (source: water resources research of Beijing-Tianjin-Hebei metropolitan area based on circular economy).