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Bureau of Hydrology, Ministry of Water Resources, Beijing 100053, China
The groundwater is not only an important component of water resources but also the major water supply source in many cities and north areas of China. It plays an important role in guarantying the people's life, promoting the economy development and improving the environment.
The mean annual amount of our country's groundwater resource is 828.8 billion m3, of which 676.2 billion m3 produced in mountainous areas; 187.3 billion m3 belong to plain areas. There are 727.9 billion m3 groundwater is the repeated surface water which occupies 86.7% of the total amount of groundwater resource.
According to the occurrence of groundwater in rocks, the groundwater resource in our country can be divided into four types: pore water in friable rock, fissured water in bedrock, Karst water and suprapermafrost water. Among them, pore water in friable rock plays an important role in the exploitation and utilization of groundwater resource in our country. It is mainly distributed in the plains and the basins, its amount is the largest and is exploded and used widely. Fissured water in bedrock is mainly distributed in the fracture zone and weathering zone of bedrock or the pore of clastic rock. It is very difficult to form a concentrated water supply zone except a few developed areas of the bank water structure. Karst water mainly distributes in Karst region, in most of the Karst region it is rich of groundwater and generally it's the source of water supply.
Precipitation and surface water are the main recharge source of groundwater. The distribution of groundwater is very uneven in our country. The calculated area of the groundwater resource of the Yellow River, the Huaihe River, the Haihe River, the Songliao River in north and the Inland occupy 61 percent of the total calculated area of China. The annual groundwater resource amount in above areas is 255.1 billion m3, only occupies 31 percent of the total groundwater resource amount of China. On the other hand, the calculated area of the Changjiang River, Zhujiang River in south and some rivers in southeast and southwest occupy 39 percent of the total calculated area of China, their annual average groundwater resource amount is 573.7 billion m3, which occupies 69 percent of the total annual groundwater resource amount of China.
Compared to other water resource, the groundwater has many advantages. First, it has good quality because it is filtrated and cleaned in the unsaturated zone in the process of forming groundwater. Second, the investment of groundwater supply engineering is very little but the efficiency is fast.
It has a long history to exploit and use groundwater in China. Before the mid of 1960s, the exploitation of the groundwater is relative little. From the mid of 1960s to the end of 1970s, it is the period of developing and utilizing groundwater in large scale in China. To the end of 1979, the total exploitation amount of groundwater in whole country reached 40 billion m3. Since 1980, with the rapid development of national economy and the sharp increasing of water consumption the exploitation amount of groundwater has been up to 109.5 billion m3 in 2001.
According to the statistics, in 2001, the total amount of water supply in whole country is 556.7 billion m3, among which 445.1 billion m3 is from surface water sources, accounting for 79.9 percent of the total amount; while 109.5 billion m3 is from groundwater sources, accounting for 19.7 percent; and 2.2 billion m3 is from other water supply sources, accounting for 0.4%. Groundwater is the important water supply source in north of China. In Hebei Province the amount of groundwater supply is about three quarters of the total amount; in Beijing City, Shanxi Province, Henan Province and Shandong Province 50%—70% water supply depends on groundwater; and in Liaoning Province, Shanxi Province, Inner Mongolia, Heilongjian Province, Tianjing City and Jilin Province about 30%—50% water supply is from groundwater.
Up to now, nearly 400 cities in China develop groundwater as their water supply source. Accounting to the incompletely statistics, more than 60 cities regarded groundwater as their mainly water supply source, such as Shijiazhuang City, Taiyuan City, Hohhot City, Shenyang City, Jinan City, Haikou City, Xi'an City, Xining City, Yichuan City, Urumqi City, Lhasa City and so on. Other cities which regarded the groundwater and surface water as their water supply are as follows: Beijing City, Tianjin City, Dalian City, Harbin City, Nanjing City, Hangzhou City, Nanchang City, Qingdao City, Zhengzhou City, Wuhan City, Chengdu City, Guiyang City, Kunmin City, Lanzhou City, Changchun City, Shanghai City and so on.
The exploitation and utilization of the groundwater contributes a lot for the national economy development and increasing people's life level. On the other hand, because it is not controlled well the serious over exploitation in many regions caused many geological problems such as the groundwater depression continually, seawater invasion, downward of salt-water interface, subsidence of land surface and desertification, etc. According to the statistics, up to now more than 160 regions have the problem of over exploitation of groundwater in China and the total area of over exploitation regions is about 180000 km2, among which the area of severely over exploitation is up to 80000 km2 occupied more than 40% of the total over exploitation area.
According to the partition of the administration, there are 24 provinces of China exist the problem of groundwater over-exploitation, among them Hebei Province is the largest one, where over-exploitation area has achieved 67000 km2, occupies 90% of its plain area.
A series of environmental and geological problem appeared because of the groundwater over-exploitation, which is as follows:
(a) Regional groundwater depression continually.
Because of the over-exploitation of the groundwater continually and with high intensity in some regions, the groundwater resource can't be recharged in time and the depression cones is enlarged, which even leads to the draining of the aquifer, reduction of water yield of a single well or discard the wells as useless and the depletion of the water resource. For instance, in Shijiazhuang City of Hebei Province because of the over exploitation of groundwater for a long time the depression cone is enlarged every year.
(b) Subsidence of land surface
The over-exploitation of the groundwater not only cause the water level declined greatly, but also lead to land surface subsidence in some areas mainly with the deep groundwater exploitation. The areas where the subsidence is very severely are as follows: Tianjin City, Cangzhou City, Xi'an City and Taiyuan City in north of China; Shanghai City, Puyang City, Wuxi City and Changzhou City in the south.
(c) Seawater Invasion
Seawater invasion is mainly occurred in the coastal regions of China. The reason is that after the large number exploitation of the groundwater, arisen the seawater circumfluence. The relatively severe areas are Dalian City in Liaoning Province, Qinghuangdao City in Hebei Province, Qingdao City in Shandong Province and so on.
(d) Ground collapse
The over-exploitation of the groundwater in bed rock region (mainly in Karst area) will lead to some bad geological phenomena such as ground collapse and fissure and so on. Ground collapse is occurred widely in our country but in the south the occurring rate is higher than the north because of the distribution of Karst water.
(e) Pollution of Groundwater
Over-exploitation of the groundwater not only quickened the infiltration of surface water but also the pollutant in the surface water so the groundwater is polluted. Once it happened it is difficult to recover. Now the groundwater resource is polluted very severely in many cities. According to the statistic there are more than 130 big and middle cities whose groundwater is polluted in varied degree and the main pollution source is industry and living pollution. The groundwater in local agricultural region is also polluted, which is mainly distributed in the sewage irrigation area of the suburb. Up to now, there is over 20 million mu * farms irrigated by sewage water that leads to the pollution of groundwater directly and the pesticide and the fertilizer pollute others.
(f) Soil desertification
The continuous decline of groundwater level will lead to the degeneration of vegetation and destroyed environment, which is the one reason of soil desertification. This phenomenon has occurred in Inner Mongolia, northwest of China and some parts of Heibei Province.
The groundwater dynamic monitoring began from the 1960s in the departments of Ministry of Water Resources. After several years' hard work we set up a groundwater monitoring network with a certain scale which provide the evidence for water resource management and reasonable development and utilization of groundwater. Now there are more than 12000 basic monitoring wells and 10000 uniformed monitoring wells. The monitoring items include groundwater level, water amount, water quality and water temperature and so on. In addition, combining the demand of groundwater exploitation and management in the departments of city construction and land resources, we lay out some groundwater observation wells and the investigate spots near the areas of water supply and of depression cones in order to monitor groundwater dynamic state.
But the work of groundwater monitor is still weak and it's difficult to meet the demand of water resources management and regulation. Many problems are still existed including the sparse density of observation wells, lack of monitoring wells in the funnel area and important water sources, the old monitoring equipments, the laggard observation and transmission method which can't ensure the information will be transmitted in time, and insufficient fund for groundwater monitor.
Currently, we have made “The Plan of National Groundwater Monitor”. We are planning to set up some stable and long term groundwater monitoring stations in the main depression cones and important areas of groundwater supply and the dynamic observation system for improving the level of groundwater monitor.
On the one side, water resource is seriously short in our country and the over exploitation of groundwater leads to many environmental and geological disasters. On the other side, the water wasting is very severely. Irrigation is the main water consumer, which occupies 70% of the total water consumption in our country. Because the irrigation method is out of date, most of the channels are soil channels plus the old facilities it is still the traditional irrigation way in most of areas. In some irrigation areas farmers even still use the flooding irrigation method, which waste water very serious. The utilization rate of industrial water consumption is not high either. The water loss through the water transportation pipe and water facilities has reached over 20 percent and the public water waste is very serious.
In order to develop and utilize groundwater more reasonably, reduce the water waste, optimize the distribution of water resource and improve the water utilization rate, in recent years we did a lot of work on the groundwater planning and strengthening the legalization of groundwater management, which is useful for restricting the groundwater over exploitation. Especially on the construction of legalization, we enact Water Law of People's Republic of China, The Executed Rule of Water Using License, Water Resource Demonstration & Management Rules of the Construction Project and so on. The Water Law revised and passed on October 29, 2002 shows us we should obey the plans approved on the water activities such as exploitation, utilization, saving, protection and management; if anyone who against the plan and lead to the river or lake degeneration, groundwater over exploitation, ground subsidence and water body pollution he would be responsible for the management. In the area of groundwater over-exploitation, the local government of the county or above should limit the exploitation of groundwater strictly. In the area of severely over exploitation we can divide the groundwater into the forbidden exploitation area and the limited exploitation area after approved by the government of the province, the autonomous region and the municipality directly under the Central Government. If exploit groundwater in the coastal regions we should take measures to avoid ground subsidence and seawater invasion after scientific demonstration. The Executed Rule of Water Using License shows us any water consumer take water from underground should apply the license from water administration department except living water consumption. The total amount of groundwater consumption can't exeed the total amount of the regional groundwater available and it must accord with the requirement of the overall arrangement and water-taking layer. Water Resource Demonstration & Management Rules of the Construction Project shows us for the new, rebuilding or expand construction projects that takes water from the rivers, lakes and underground directly, the owner of the construction projects must apply the water license, and should carry out the water resource demonstration and compile the report.
Strengthen the research on groundwater analysis is the basis of the scientific management of groundwater. Recent years we did a lot of work on groundwater analysis, the details are as follows.
The first national water resources assessment was carried out at the beginning of 1980s. During this period we did national groundwater assessment, submitted the results of groundwater assessment and provided important evidences for groundwater planning and management. But in the past 20 years, both of surface water and groundwater varied greatly because of human activities. Thus it is necessary for us to hold the national water resources assessment again. Now we are organizing to do the national water resources planning. The first work we should do is water resources assessment, which includes the national groundwater assessment. It is estimated that this work will be finished in two years. At the same time, combining the national land resource investigation in recent years, we also carried out the initial investigation of groundwater, which has been finished. Recent years “Water Resources Bulletin in China” is published every year in Ministry of Water Resources, which shows us the condition of groundwater development and utilization. In additional, groundwater assessment is also done in many important projects such as Demonstration on the Engineering of Diverting Water From the South to North, Water Resources Planning in North of China, etc., which provides some basic information for reconnaissance and planning of engineering.
In order to provide groundwater dynamic information to the department concerned in time, Hydrology Bureau of Ministry of Water Resources is organizing to establish a real time dynamic monitoring system of groundwater, which provides groundwater monitoring information on time through internet and reflects the dynamic variation in real time.
Many institutes and experts did a lot of work on the prediction of groundwater analysis.
At present there are many ways to do the dynamic prediction of groundwater level. The main method is to set up a model of groundwater movement and simulate the process of groundwater movement and predict the state. Using the traditional groundwater dynamic model we developed a lot of research work in Liaoning Province, Shandong Province, Jiangsu Province, Inner Mongolia, Xinjiang municipality and Anhui Province. Recently, we imported some groundwater analysis model from abroad such as MODELFLOW, ASMWIN and so on. We did some experiments with these models in Anhui Province and Shandong Province and got some achievements. Because of the spatial variation of the character of groundwater aquifer the parameter of groundwater is uncertain and some precise physical concept models have a great limitation on expressing the interrelation of every part of groundwater system. According to the mapping relation between the groundwater level and its influence factors, many experts simulate the dynamic variation of the groundwater level with the ANN model proposed by Dr. Rogers from Standford University. We carry out the experiments in some areas in Henan Province and Hebei Province and acheive good results.
On the prediction of ground subsidence, through the research of ground subsidence caused by groundwater over exploitation in Suzhou City of Jiangsu Province, Professor CHEN Chongxi established a mathematic model accord with the geological condition and subsiding mechanism, ascertained the relative parameters, predicted the amount of ground subsidence under the groundwater exploitation and proposed some countermeasures to prevent ground subsidence in groundwater exploitation.
In order to protect the environment, many experts carried out a series of studies on the relationship between groundwater and ecosystem. According to the research on the vegetation growth and groundwater dynamic variation in northwest arid region, we think the best embedding depth of groundwater to develop groundwater is in the depth of 4—5 m, which is benefit for vegetation growth and salinization prevention.
In China groundwater pollution is sharply increasing every year because of the surface water pollution, irrigation with sewage water and unreasonable utilization of groundwater. Groundwater pollution has the characteristics of point, line and side distribution. The point pollution indicates the local severe pollution around the city and town or the farm because of the concentrated population, developed industry and feedlot with middle or large scale in rural areas. The line pollution indicates the groundwater pollution around the river caused by river pollution. The side pollution means the irrigation with sewage water and the pollution of misusing fertilizer and pesticide in agriculture.
In recent years, we strengthened the work of water quality monitor and assessment in departments of water resources and achieved many analysis and assessment results. At the same time in order to protect the safety of water quality of water supply system, combining the rules of water using license, we constituted the rule of water quality management of the license of using water which indicates that the water taken from underground should be inspected and the water quality must meet the demand.
In 2000 according to analysis of groundwater quality done by Ministry of Land Resources in 130 cities and areas of China, it can be considered the total water quality of groundwater in China is well but in most of the cities the groundwater is suffered point and side pollution, which results in exceeding standard of some elements in local regions. The main polluting elements are the degree of mineralization, the total degree of hardness, sulphate, nitrate, nitrite, ammonia, nitrogen, chlorid, fluorid, pH value, iron and manganese, etc. According to the pollution degree, the pollution of north cities is much higher than south cities where the pollution elements are more and exceed the standard rate. Especially in north of China the pollution is most outstanding.
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