Yuan Xilong
(Qingdao Geological Engineering Survey Institute, Qingdao 266071)
Author's introduction: Yuan Xilong (1964-), male, senior engineer, is mainly engaged in the research of hydrogeology, environmental geology and computer technology application.
Abstract: Qingdao City, Shandong Province is a region with poor water resources and uneven distribution of groundwater resources. This paper summarizes the general law of the development and protection of groundwater resources through the history of the development of groundwater resources in Qingdao City, the current situation, as well as the occurrence, development, dynamic changes, and management countermeasures taken in the environmental geological problems caused by irrational development of groundwater resources, and introduces the general law of the development and protection of groundwater resources at the same time, while introducing the seawater At the same time, it introduces the utilization of groundwater in the invasion area for marine aquaculture, and groundwater in the urban construction area for geothermal air conditioning, etc.; as well as the technological methods of increasing the water output of a single well for water extraction in the fissure water where the permeability of the aquifer is relatively poor, and in the slope-flooded area and the weathered zone of granite where the thickness of the aquifer is relatively small.
Keywords: Qingdao; groundwater; development and utilization; protection; groundwater extraction technology
Qingdao is located in the southwestern part of Shandong Peninsula, bordering on the Yellow Sea in the southeast, and bordering on Weihai, Yantai and Weifang in the surrounding area. Qingdao is a relatively poor water resources, per capita possession of available water resources is 170m3, accounting for 1/4 of the national per capita water resources; at the same time, Qingdao's rapid economic development, the demand for water resources is also increasing, increase the source of concurrently with the flow of water is to alleviate the contradiction between supply and demand in Qingdao City, an effective way.
1 hydrogeological profile
Qingdao City, the geomorphology type of low hills, denudation - accumulation of quasi-plains, and between the mountain valleys, flood plains in front of the mountains, local mountains (Laoshan). According to different geomorphological and hydrogeological features, the area is divided into three hydrogeological zones: (1) Jiao Bei low hills hydrogeological zone, (2) Jiao Lai Basin hydrogeological zone, (3) Jiao Nan - Laoshan in the low hills hydrogeological zone (Figure 1). Groundwater types include loose rock-like pore water, clastic rock-like pore fissure water, ejecta rock-like pore fissure water, carbonate rock-like fissure karst water, and blocky and layered rock-like fissure water. Loose rock pore water is the main water-bearing rock group in Qingdao City, mainly distributed in the middle and lower valley plains of large and small rivers such as Dagu River, Baisha River-Chengyang River, Baima-Jili River, Wanggezhuang River, Yanghe River, Zhoutong River, Zhangcun-Licun River, etc., as well as the pre-sanctuary plains on the southwest side of Dazhe Mountain, and the water-bearing rock group is mainly made up of sands and sandy gravels with different grain sizes of the Quaternary alluvial and alluvial deposits with the general thickness of 5-15m, and the water yield of a single well can reach 1000m. The water output of a single well can reach more than 1000m3/d, of which the Dagu River, Baisha River - Chengyang River downstream valley plain groundwater is an important water supply source for Qingdao City, and its recoverable resources are 7951 × 104m3/a, 2367.6 × 104m3/a. ② Carbonate rock fissure karst water-bearing rock groups are mainly distributed in Pindu, Laixi, JiaoNan Wangtai also has a small distribution, water-bearing rock groups in the Fenzhishan Group, and the water-bearing rock group is the Fenzhishan Group. The rock group is the marble in the powder mountain group, the fissure is more developed, the depth is generally limited to 100m, rich in karst fissure water, especially in the tectonic and geomorphological conditions of the favorable sections, water-rich, single well water output of 500 ~ 1000m3 / d, water quality is good. However, because of the small distribution area, the water supply is more limited. (iii) Ejecting rock pore and fissure water-bearing rock groups are mainly distributed in Jimo, Jiaozhou, Laixi and Chengyang, the water-bearing rock groups are basaltic rocks in Qingshan Group and Wang's Group, the pore and fissure are more developed, the depth is generally 30-50m, the water-rich nature of the strong, single well water output of 500-1,000m3/d, and the quality of water is good, and it can be formed into a small source of water supply for the local area. The water-bearing rock groups of clastic rocks are mainly distributed in Jiaozhou, Jimo, Laixi, etc. The water-bearing rock groups are sandstones of Cretaceous Laiyang Group, Wang's Group, sandstone shale and tuffaceous sandstone shale, and the water output of a single well is generally less than 50m3/d due to the fact that their pores and fissures are not developed, and their water permeability and water-richness are all weak. 5) Water-bearing rock groups of blocky and layered rocks with fissures are mainly distributed in Laoshan Mountain, Dazeshan Mountain, and a large area of Jiaonan. The water-bearing rock groups are mainly distributed in Laoshan, Dazeshang and a large area of Jiaonan, and the water-bearing rock groups are granite, granodiorite, gneiss, metamorphic rock, schist and so on. The depth of the weathering zone is generally not more than 30m, the water richness is weak, the water output of a single well is less than 30m3/d, the local tectonic fissure dense zone is more water rich, the water output of a single well can be more than 100m3/d, the maximum can reach 500m3/d, but the distribution is very uneven, only for the local water supply.
Figure 1 Hydrogeological zoning map of Qingdao City
2 Groundwater resources development and major environmental geological problems
2.1 Groundwater resources development history and current situation
Qingdao City, as a centralized water supply for cities and towns, began in 1920, the Baisa River - Chengyang River downstream was first used as a water supply for the Qingdao City water supply, and in the early days of the founding of New China, the daily water supply capacity reached 3.0×104m3/d, and the daily water supply capacity reached 3.0×104m3/d. The daily water supply capacity reached 3.0×104m3/d; before the 1970s, subject to the constraints of economic and technological level, the exploitation of groundwater resources grew slowly, and in the late 1970s, the development of agriculture and industry accelerated, and the exploitation of groundwater resources increased rapidly, and the extraction and replenishment of groundwater resources appeared in the negative equilibrium, and the water level continued to decline, and in the mid-1980s, the sections of the Dagu River and the Baishe River-Chengyang River water supply area were In the mid-80's, the Dagu River, Baisha River - Chengyang River water source area and other sections of the river had a groundwater landing funnel, which successively produced different degrees of sea (salty) water. In the late 90's, through a series of measures such as decreasing the amount of groundwater extraction, constructing seawater intrusion intercepting walls, and constructing rubber rolling dams in the river to intercept the surface water to increase the amount of groundwater replenishment, seawater intrusion has been effectively controlled. In Qingdao, the average amount of extractable groundwater resources for many years was 6.3436×108m3/a, and the amount of natural recharge resources in 2002 was 5.0586×108m3, and the actual amount of groundwater extracted in 2002 was 6.1098×108m3, which accounted for 54.17% of the total amount of freshwater supplied, and the amount of extracted groundwater was the highest in the history of 1989, amounting to 6.78×108m3, and the amount of extracted groundwater was the lowest in recent years in 1999, which was the lowest in recent years. In 1989, the mining volume was the highest value in history, amounting to 6.78×108m3, and in 1999, the mining volume was the lowest value in recent years, amounting to 5.38×108m3. Qingdao region's many years of mining practice basically reflects the level of exploitation and storage capacity of groundwater in the region, which shows that Qingdao region's degree of exploitation and utilization of groundwater resources is relatively high, and it is basically a balance of extraction and replenishment, but due to the differences in urban and rural layouts and the differences in water demand, the exploitation volume in some areas is too large, forming a funnel for the landing of groundwater, and the exploitation volume in some areas is small. However, due to the differences in urban and rural layout and different water demand, some areas are over-exploited, forming a groundwater funnel, while some areas are under-exploited.
2.2 Environmental Geological Problems Related to the Development of Groundwater Resources
2.2.1 Seawater Invasion
Since the late 1970s to the early 1990s, there was over-exploitation of groundwater resources in most of the water-rich areas, and there were groundwater descent funnels, and seawater invasion of varying degrees occurred in the downstream near-sea areas of various rivers. The most serious is in the mid-80's, sea (salt) water invasion led to a large number of wells scrapped, grain fields deserted, water quality deterioration; 90's after the invasion of the area near the exploitation of a substantial reduction in precipitation than the 80's increase in the groundwater level has varying degrees of rebound, part of the funnel leveled off, the momentum of the sea (salt) water invasion has been slowed down, invasion of the area of the slight recession. 2002 for the year of the special dry year, the groundwater level of some regions 2002 was a particularly dry year, the groundwater level in some areas continued to fall, and the invasion area expanded again. At present, the sea (salt) water intrusion in Qingdao mainly occurs in the lower reaches of the Dagu River, Baisha River - Chengyang River, the lower reaches of the Yanghe River, Huangdao Xin'an, Pingdu Xinhe - Grey Port area, the invasion area of each place in June 2002, as shown in Table 1.
Table 1: Distribution of the current distribution of sea (salt) water intrusion in Qingdao City in June 2002
2.2.2 Water pollution
Rapid development of industry, urban domestic sewage, industrial wastewater, and industrial waste water, the rapid development of the city, the rapid development of industrial wastewater. The rapid development of industry has increased the discharge of sewage and industrial wastewater in cities and towns, and the development of agriculture has increased the application of pesticides and chemical fertilizers. During the period when sewage treatment technology, facilities and relevant laws were not yet perfect, the rivers were seriously polluted, and the polluted water recharged into the groundwater, which led to the contamination of the groundwater quality. District groundwater quality exceeds the standard indicators are mainly mineralization, hardness, phenol, manganese and other items, of which the phenomenon of exceeding the standard is more prevalent, the local exceeded tens of times, the typical contaminated groundwater main anion composition as shown in Figure 2, as can be seen in the figure The content of 25% has reached the standard of participation in the chemical type of water naming.
Figure 2 Pie chart of the main anion composition of contaminated groundwater in Dagu River water source area
In addition to industrial wastewater pollution in addition to agricultural pollution is not to be ignored, groundwater contamination is closely related to the agricultural surface pollution, in 2000, Qingdao region, the arable land area of 546,000 hectares, pesticide application amounted to 7,451 tons of total pesticide use, an average of 18.7 kilograms of pesticide use per hectare. The total amount of fertilizers applied was 342,000 tons, with an average of 681.2 kilograms of fertilizers per hectare of arable land. Some of these fertilizers and pesticides are absorbed by crops, some are decomposed or chemosynthesized, and the remaining part will be recharged into groundwater with rainfall. Long-term excessive and irrational application of chemical fertilizers caused by the main environmental problems are manifested in: First, through surface runoff pollution of water bodies, so that rivers, reservoirs and other bodies of water eutrophication; second is infiltrated into the ground to cause groundwater pollution, resulting in nitrate exceeds the standard; third is to pollute the soil, so that the soil organic matter to reduce the soil's physicochemical properties and fertility.
3 Groundwater resources protection and environmental geology issues of governance countermeasures
For the problems existing in the development of groundwater resources, the relevant departments after investigation, research, proposed and implemented the corresponding governance measures.
3.1 Governance of seawater intrusion
3.1.1 Underground interception wall
In order to protect the water source of Dagu River and increase the amount of recoverable resources of Dagu River water source, after the hydrogeological survey of water supply to the water source of Dagu River in 1985～1986, and the survey of underground reservoir of Dagu River in 1990, the water source of Dagu River was constructed by the Qingdao Municipal Government from 1997～1998. In 1997-1998, Qingdao Municipal Government invested in the construction of Dagu River water source Xiaoma Bay interception wall project, the interception wall is 14.2km long, using continuous pendulum spraying method, the depth of pendulum spraying reaches the bottom of the aquifer, which cuts off the downstream of the wall of the sea (salty) water backwater, so that the phenomenon of the invasion of the sea (salty) water has been curbed to better play the water supply of the water source of Dagu River to provide a guarantee for the engineering measures. 2001, and carried out the downstream of the Baisa River to build an underground interception wall Feasibility study of the construction of underground cut-off wall.
3.1.2 Construction of Rubber Roller Dams in the Downstream of the River
In the 1980s, when seawater intrusion occurred in the downstream water source of Baisha River - Chengyang River, a special hydrogeological investigation of seawater intrusion was carried out, and then a number of rubber roller dams were constructed in the river channel of Baisha River, to stop the river water, to increase the amount of groundwater recharge, and accordingly to reduce the amount of groundwater mining, so that the groundwater The descending funnel was gradually narrowed, effectively slowing down the rate of seawater intrusion. In addition, the Dagu River, Wanggezhuang River, Yanghe River and other rivers are built on the river water storage rubber rolling dams, play a role in the artificial recharge of groundwater.
3.1.3 Construction of river downstream (anti-tidal backwater) barrage
When the storm surge, high tide, in the absence of water-blocking structures in the estuary, seawater will be upstream of the river and recharge the groundwater, which is another reason for seawater intrusion, in the seawater upstream of the river is serious in the estuary, the selection of the appropriate location of the barrage was built to block seawater, but also can be intercepted to save freshwater, increasing the fresh groundwater. The construction of barrages at appropriate locations, which can block seawater and also store fresh water, increase the replenishment of underground fresh water, has also played an important role in preventing seawater intrusion. Another should be prohibited sand dredging in the riverbed, so as not to lower the riverbed, resulting in seawater upstream distance increased to prevent the destruction of the cover layer and increase the rate of seawater infiltration.
3.2 Groundwater Pollution Control
3.2.1 Establishment of Water Source Protection Zone through Legislative Means
Qingdao Municipality has promulgated and implemented the "Qingdao Municipal Environmental Protection Regulations for Sources of Drinking Water for Daily Use" through legislative means, which stipulates that the water sources for domestic water that have been designated and announced are protected by law, and explicitly prohibits the discharge, stockpiling, and construction of the relevant Seven kinds of behavior; for the first time the announcement of the groundwater source protection zone there are 11, respectively, Dagu River, Jimo Wuqibu, Jimo Dongguan, Jimo East Barrier, Jimo Mashan, Pingdu Yunshanzhiling, Jiaozhou Dianzi River, Jiaonan Jiyang River, Chengyang Baishaxi River, Jiaozhou Beiguan basalt area, the protection zone has a clear geographic boundaries and marking the protection of the water source with a legal basis to protect the source of groundwater play a positive role in the protection of groundwater sources.
3.2.2 Pollution source management
Since 1998, Qingdao City, through the formulation of relevant regulations, focused on the Dagu River Basin pollution source management, 27 key wastewater on both sides of the river over the discharge of enterprises to carry out time-limited treatment, and 16 enterprises have been shut down and transferred to outlaw the small-scale mining and processing 540 mining sites, and at present, the establishment of a daily sewage treatment capacity of 5 × 104m3 / d sewage. 104m3 / d sewage treatment plant 6, in the management of the above measures, the Dagu River, Baisha River and other river water quality has improved significantly, the degree of groundwater pollution is reduced, but there is still a great distance from the eradication of pollution, restoration of groundwater quality.
4 Application of groundwater resources of different water quality to different industries or fields
4.1 Development of saline groundwater resources for aquaculture in seawater intrusion areas
Qingdao has a coastline of 730 km, rich in seafood, and a developed marine aquaculture industry, which used to utilize seawater for marine aquaculture, but the seawater temperature varies considerably with different seasons. However, the water temperature varies greatly from season to season, and the water temperature has a great influence on mariculture, especially on seafood nursery, and the low water temperature needs to be heated by boilers, which increases the construction investment and operation cost. In the vicinity of the coastline, are distributed with varying widths of native or human-induced seawater intrusion (saltwater) belt, in recent years, mariculture began to drill wells near the coastline to exploit the salty groundwater for mariculture, its constant water temperature, good water quality than the direct use of seawater has obvious superiority, the rapid popularization and application of this technology.
4.2 Development of groundwater resources in cities and towns or industrial zones for ground temperature air conditioning
Qingdao City, in order to reduce air pollution, outlawed unit heating boilers, promote the application of ground temperature air conditioning, the use of shallow groundwater as a source of thermal water, the shallow groundwater water temperature of the region of 14 ℃ or so, in order to achieve long-term stability of the use of the construction of ground temperature air conditioning need to construct two water wells, one of which is used for pumping, the other is used for injection, pumping out water, the other is used for injection, the other is used to pump out water, the other is used for injection. The other one is used for water injection, the groundwater pumped out by the air conditioning equipment for thermal energy conversion, the temperature of the discharged water is about 7 ℃, and through the injection wells back into the aquifer, the two wells to retain a certain spacing, in order to back into the aquifer of the lower temperature of the water can be fully absorbed by the ground temperature, and then warmed up to 14 ℃ or so, to achieve the purpose of recycling.
5 Weak aquifers to increase the water yield of a single well water extraction technology
Qingdao City, in addition to a small range of river valleys, pre-mountain alluvial flood plains, marble karst water-rich areas and basalt pore and fissure water-rich areas, most of the areas of aquifers or water-bearing formations of poor hydraulic conductivity, the ordinary wells are very difficult to obtain a satisfactory single-well water influx, these areas, although there is a more adequate recharge resources, but by the water extraction Although these areas have more adequate recharge resources, but by the limitations of water extraction technology, the degree of exploitation and utilization of groundwater resources is low, in such areas there are two methods of water extraction technology more successful to achieve the purpose of increasing the water output of a single well, and the construction cost of its wells is lower, it is worthwhile to popularize the application.
5.1 Large-mouth well mining bedrock fissure water
Qingdao City, large-mouth wells are generally 5 to 50m in diameter, well depth is generally 10 to 15m, the single-well influx is generally 500 to 2000m3 / d, mainly in granite, metamorphic rocks and other fissure water distribution area, the method of formation of wells is generally manual or mechanical open excavation, and then stone masonry retaining wall; mainly used for agricultural irrigation, a small number of large wells. Agricultural irrigation, a small number of large wells are also used for urban centralized water supply, Jiaonan City Water Plant in the mountain slopes of the floodplain area successfully constructed a 50m diameter large well for urban life centralized water supply, the daily water supply capacity of 2000 ~ 5000m3 / d. Large wells to increase the amount of hydrogeological principles: in other conditions remain unchanged greatly increase the cross sectional area, thereby increasing the aquifer flow into the well. The amount of water flowing into the well is increased. The main advantage of large wells is that more groundwater can be extracted from weak aquifers, which increases the water consumption of a single well and facilitates extraction and management. The main disadvantages are: ① the water quantity varies greatly with the seasons, and the water quantity decreases in the dry years; ② due to the large caliber of the wells, dust or other debris can easily fall into the wells with the wind, which affects the water quality. Improvement direction: by backfilling gravel in the well, create artificial aquifers, buried in the bottom of the well horizontal collection pipe, directly in the collection pipe to extract groundwater. This can achieve two purposes: ① easy to manage, safeguard water quality; ② less occupied arable land, protect the natural landscape.
5.2 Small-diameter well group extraction of weak aquifer pore water
Small-diameter well group extraction method is a number of small-diameter wells, through a connecting water pipe (horizontal water collection pipe) will be connected together to form a unified outlet, the use of vacuum counterparts to extract groundwater pumping. The diameter of the small-diameter wells is generally 5-8cm, the depth of the wells is generally 10-15m, the horizontal spacing is generally not less than 2m, and the number of small-diameter wells is generally 3-6, depending on the hydraulic conductivity of the aquifer and the amount of water to be extracted from a single well. The well type in the northeastern part of Pingdu City, the front of the mountain, the slope of the mountain floodplain area of farmland irrigation applications, achieved better water extraction results.
6 Conclusion
The development of groundwater resources in Qingdao City has gone through a course from disorder to order, and also experienced the process of generating environmental geological problems to the governance of environmental geological problems, and paying insufficient attention to the protection of groundwater resources to the process of legislative protection, and some successful experiences have been made, but it is still a long way to go for the restoration of the hydrogeological environment of the region, and to achieve the goal of the sustainable development and utilization of groundwater resources. There is still a long way to go. This paper introduces the application of groundwater resources and water extraction technology methods, aims to continue to be able to explore the application of groundwater resources and weak aquifer water extraction technology, better and more extensive development and utilization of groundwater as a renewable resource for economic development services.
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