First, find water and supply water.
As early as 1980, a general survey of hydrogeology was carried out in China, covering an area of about 8.2 million km2, and basic data were obtained for the use of national planning and construction and relevant industrial departments. In addition, nearly 6.5438+0.3 million km2 hydrogeological exploration of water supply in agricultural and pastoral areas has been completed, which provides a scientific basis for farmland water conservancy planning, guiding well irrigation area to expand irrigation area, improving saline-alkali land and treating cold-soaked fields.
Since the late 1970s and early 1980s, China has transferred to key economic development areas, such as Huanghuaihai Plain, Jixuhuai Area, Yangtze River Delta, Northeast Economic Zone, Beijing-Tianjin-Tangshan Area and Northwest Energy Base, and has achieved many important research results.
Since 1980s, many special investigations have been carried out, such as the enrichment of groundwater in red beds, basalt and loess areas, and groundwater in northern karst areas and typical karst areas.
Hydrogeological surveys have been carried out in more than 200 cities to varying degrees, and more than 200 centralized groundwater recharge sources have been evaluated in more than 80 cities with serious water shortage, which has greatly eased the water supply shortage in these cities. The water resources of 75 major cities such as Beijing, Tianjin and Shanghai are predicted, and the water resources of coastal open cities such as Shenzhen, Xiamen, Dalian and Beihai are demonstrated in combination with urban development planning. Beijing, Tianjin, Fuzhou, Lhasa, Zhangzhou, Zhanjiang, Kunming, Zhengzhou, etc. 10 cities with geothermal resources development prospects have carried out exploration and research on geothermal fields.
In the long-term practice of water search in water-deficient areas, a set of effective methods and experiences have been summarized, such as "new structure water control" (Xiao Nansen), groundwater network theory (Hu Haitao) and water storage structure theory (Liu Guangya, Qian Xuepu, etc.), which are valuable explorations for water search in bedrock areas.
Since 1995, the special plan for water exploration in northwest China has been implemented, and potable fresh water has been found in the hinterland of Taklimakan desert and remote areas of Ningxia, northern Shaanxi and Inner Mongolia. With the new round of land resources survey by the Ministry of Land and Resources and the implementation of water exploration projects in karst mountainous areas in northwest and southwest China, it is of great significance to the country's large-scale development in the western region where water resources are scarce
Second, the groundwater resources evaluation
On the basis of hydrogeological investigation, the evaluation methods of large-scale groundwater resources are preliminarily summarized for different types of groundwater in Beijing, northern Shaanxi, eastern Henan, central and western Jilin and Hexi Corridor. ① For the over-exploited city of Beijing, the total amount of precipitation, rivers and groundwater resources in the whole region is predicted and calculated by regions, and the scheme of evaluating the exploitation amount and protecting the groundwater resources in Yongding River area by artificial storage is put forward. (2) The evaluation of groundwater resources in the agricultural and forestry areas of the Loess Plateau was carried out, and it was confirmed that fissure phreatic water in loess caves and confined water in bedrock fissures are two main types of groundwater in typical loess plateau areas. For loess, an anisotropic and vertically heterogeneous aquifer, we should not only choose various hydrogeological parameters, but also pay attention to the relative layering and bearing capacity of bedrock cracks under loess, so as to put forward a complete model for groundwater resources evaluation in loess plateau area. ③ Evaluate groundwater resources in key areas of national economy in combination with specific hydrogeological conditions. For example, in Jilin Province and Songnen Plain, the characteristics of multi-layer overflow recharge are fully considered, which makes the evaluation results closer to the actual situation. Shangqiu area in Henan Province mainly considers the lithologic structure of vadose zone and water level fluctuation zone, and improves the previous methods for determining precipitation infiltration coefficient, precipitation water supply in water level fluctuation zone and phreatic water evaporation limit depth. A numerical simulation model of groundwater in 6000km2 large watershed of Hexi Corridor is established. After in-depth analysis of the distribution of aquifer systems in various hydrological basins and the conditions and processes of groundwater recharge, the aquifer areas available for development and utilization are delineated. (4) Carry out research on water resources evaluation, development and utilization in North China. It is estimated that the total regional water resources are 41.900 million m3/a, the available amount is 31.000 million m3/a, and the brackish water and shallow confined water with salinity of 2-3g/l are 5.3 billion m3/a, of which the total water resources in Beijing, Tianjin and Tangshan are1.1. ⑤ Special types of groundwater resources are also evaluated. For example, the recoverable resources of deep underground brine in Sichuan Basin are estimated to be 983 million m3, and the remaining recoverable resources are 762 million m3. The static reserve of underground hot water in Tianjin is 584,465.438+0 billion m3, and the recoverable amount is 825 million m3.
Since the founding of the People's Republic of China, 832 underground water sources have been identified 1243, including large-scale water sources (the allowable exploitation amount is above 5× 1× 104 ~ 5×65438) and medium-sized water sources (the allowable exploitation amount is1× 65438) 490. According to the types of water-bearing media, there are 846 pore water types (68%), 3 15 karst water types (25%) and 82 fissure water types (7%).
According to the characteristics and classification of groundwater resources, the author thinks that groundwater resources are systematic, mobile, recoverable and controllable. This is because groundwater is distributed in a certain range, can flow in the aquifer and can be replenished regularly. When the recharge is sufficient, the original water quantity can be restored, and the storage of groundwater plays a regulating role in the process of hole filling and drainage. So it is different from solid mineral resources and fluid mineral resources such as oil and natural gas. There are many schemes to classify groundwater resources, such as natural resources and exploitation resources, recharge, storage and consumption, recharge and storage resources, and so on. In recent years, on the basis of summarizing all kinds of classification of groundwater resources in the past, a classification scheme has emerged, which is divided into recharge resources and storage resources from the perspective of groundwater resources composition, and into allowable resources and resources that are difficult to use from the perspective of exploitation. In the evaluation of groundwater resources, the actual amount of groundwater to be calculated includes recharge, storage and allowable exploitation.
Three. Groundwater resources management
Since the 1980s, an important symbol of groundwater resources research is to gradually shift the main goal to the research of management mode, that is, on the basis of mastering the distribution and quantity of groundwater resources, to study how to rationally develop, utilize and protect groundwater resources, so as to make them in the most favorable state for human life and production, so as to obtain the greatest economic, social and environmental benefits. It involves natural environment, social environment, technical and economic environment and other issues related to groundwater development activities. Through the mathematical model and optimization technology of groundwater flow, the groundwater management model is established to realize the management goal. The research on groundwater resources management has made rapid progress. From the types of management models, there are centralized parameter model, distributed parameter model, water quantity management model, water quality management model, economic model and the combination model of the above models, single-objective planning model and multi-objective planning model, single groundwater management model or surface water management model, and surface water and groundwater joint management model. From the management content, it has developed from the general water policy and water balance management in the past to the management of groundwater dynamics and water resources (including water quantity and water quality), the joint operation management of surface water and groundwater, the land use and groundwater dynamic control management to control geological disasters, and the multi-level and multi-objective management to comprehensively consider the side effects of ecological environment caused by water resources development and utilization and the prevention, control and improvement of economic and technical constraints. The theory of groundwater resources management has matured.
The research of groundwater resources management in China started a little late, but it developed very rapidly, and a large number of research results of groundwater resources management aimed at different regions and different management problems appeared. For example, the groundwater resource management model in Shijiazhuang City, based on the overall concept of systematization, modeling and optimization, integrates water quantity model, water quality model and optimization model, which provides a feasible comprehensive management decision-making scheme for controlling the development of groundwater falling funnel in Shijiazhuang City and preventing the deterioration of water quality. In this paper, the multi-objective programming method is used to establish the agricultural water analysis model and the inter-basin water transfer model with the goal of maximizing the economic output value. Aiming at Xinxiang, Pingdingshan, Beijing, Xi, Shenyang, Tangshan, Handan, Beihai and other cities, according to different goals and requirements, the water resources management mode or the joint mode of water quality and quantity, the joint dispatching mode of surface water and groundwater, and the planning management mode of optimal distribution of industrial, agricultural and domestic water in the whole basin have been established, and important research results have been achieved.
Four, the environmental problems caused by the development of groundwater resources
Since the 1970s, due to the rapid development of cities and the increasing water supply in cities, environmental geological problems (or negative environmental effects or geological disasters) caused by over-exploitation of groundwater, such as water depletion (such as the continuous decline of groundwater level and the daily decrease of large spring flow). ), ground deformation (such as ground subsidence, karst collapse, ground fissures, etc. ), water quality deterioration (such as seawater intrusion, etc. ) and the deterioration of the ecological environment have aroused widespread concern. In China, many cities have carried out geological hazard exploration. Based on the analysis of the formation mechanism of geological disasters and the study of groundwater management mode, some measures such as adjusting mining layout or artificial recharge are put forward to prevent or control geological disasters.
Shanghai, Tianjin, Xi, Suzhou, Wuxi, Changzhou and other cities have carried out land subsidence research, and made progress to varying degrees. For example, the land subsidence in Shanghai has been studied since the 1960s, and the mechanism of land subsidence has been basically found out. Comprehensive control measures such as artificial recharge have been taken, and it has been basically controlled since the 1970s. Since 1980s, based on the quasi-three-dimensional groundwater flow model and the one-dimensional model describing land subsidence, the possible subsidence under different mining-compensation ratios has been predicted by numerical simulation. Therefore, the study of land subsidence has shifted from qualitative to quantitative.
In China, no matter in the north or the south, the karst collapse has been deeply studied, the types, characteristics, formation conditions and formation mechanism of karst collapse have been systematically analyzed and summarized, and the specific prevention measures have been put forward. Some researchers have also tried to study the prediction of karst collapse.
Dalian, Laizhou, Longkou, Yantai, Qingdao, Beihai, Guangxi and other places in Liaoning Province have made a detailed study on seawater intrusion in coastal areas. The mathematical model describing seawater intrusion has gone through the development from saltwater abrupt interface model to solute dispersion model in transition zone, from two-dimensional model to three-dimensional model, from model without considering density change to model with considering water density change in transition zone, and tends to be perfect. In the aspect of prevention and control countermeasures, some measures are put forward, such as adjusting exploitation quantity, artificial recharge and setting waterproof curtain. In addition to adjusting the groundwater exploitation in coastal aquifers, other control measures are rare in China.
In addition, ground fissure is another special ground deformation phenomenon related to groundwater exploitation. For example, there are many ground fissures in Xi 'an, which have caused serious harm to urban buildings. After a long-term and in-depth study, it is considered that neotectonic movement is the internal cause of the formation of ground fissures, while a large number of groundwater exploitation is the main external cause, which has stimulated the development of ground fissures.
In order to control land subsidence, store energy and increase groundwater recharge, Tianjin, Shanghai, Beijing, Yantai, Shandong and other places have carried out artificial recharge or related experimental research. The infiltration mechanism of artificial recharge is discussed, and the recharge experience under different hydrogeological conditions and the effect of controlling land subsidence or regulating energy storage are summarized.
The basic concept and theory of verb (the abbreviation of verb)
Since Toth put forward the theory of regional groundwater flow in 1960s, especially the penetration of systematic view into various fields of science and technology, many hydrogeologists have tried to study hydrogeological problems with systematic theory, and successively put forward the concepts of "groundwater hydrological system", "aquifer system", "groundwater system", "groundwater flow system" and "hydrogeological system", which have had a great impact on the development of hydrogeology. However, due to different viewpoints and angles held by different scholars, the definition and understanding of this concept are also different. Many scholars believe that the occurrence, distribution, movement and evolution of groundwater are systematic, and the word "groundwater system" has been mentioned by more scholars. Groundwater system includes "groundwater aquifer system" and "groundwater flow system". The former refers to the water-bearing rock series with unified hydraulic connection composed of aquifer and water-resisting or relatively water-resisting rocks, while the latter refers to the underground water body with unified temporal and spatial evolution process composed of stream surface groups from source to sink. They all have the characteristics of integrity and hierarchy. At present, the theory of groundwater flow system has developed rapidly in theory and method. Toth and others focus on the study of groundwater flow system with large temporal and spatial scale, which is mainly used to predict the distribution of oil and gas reservoirs. Toth also put forward the concept of "gravity cross-layer flow", which extended the flow system theory to the field of heterogeneous media.
With the exploration of water in bedrock area and the evaluation of large-scale groundwater resources, some basic research has been paid attention to. Rutian deduced from the field phenomenon and proved by experiments that the cross flow of fractured water has three important hydraulic characteristics: in a cross fracture, the water in one fracture is totally or partially deflected to another fracture when passing through the cross; The flow resistance effect in the two directions is not equal; The water inflow is not equal to the water displacement, that is, the phenomenon of partial flow occurs. On this basis, the basic models of groundwater network deviation and conditional deviation in bedrock area are derived. For another example, in the study of water characteristics in vadose zone, ① it is considered that the influence of temperature on soil water movement depends on the type of soil surface boundary conditions; When the soil surface is the boundary of pressure head, temperature has a very obvious influence on soil moisture movement. ② Lag mainly changes the distribution of soil water content; When water absorption and dehydration cycles occur, the hysteresis phenomenon has a significant impact on soil moisture movement. ③ The research of zero flux method, neutron measurement method and WM-I negative pressure gauge, as well as the application in the characteristics of hydrothermal gradient of rock and soil, unsaturated permeability coefficient, regularity of water-holding curve in the process of three-water transformation, have made the theoretical research of soil vadose zone reach a higher level.
Some new theories in other disciplines, such as grey system theory, geostatistics and fractal theory, have been popularized and applied in hydrogeology research. Groundwater system is a grey system with uncertain information. Grey system can be described by grey parameters, grey equation and grey matrix. The grey system can be controlled in the grey domain, that is, within a certain upper and lower limit. Geostatistics fully considers the spatial correlation of geological variables in a certain space, that is, it thinks that such random variables have spatial structure, so it can effectively use the information lost by classical statistics to make a more accurate evaluation of geological variables. For example, for hydrogeological variables with sparse spatial distribution but long observation time series (such as groundwater level), we should make full use of not only the spatial structure of the data, but also its time structure, and draw the water level isoline map by using the spatio-temporal kriging method, which obviously improves the quality of the map. Both grey system theory and geostatistics embody the combination of certainty and randomness. Their introduction and application have produced a series of new hydrogeology application theories.
The model and simulation of intransitive verbs
Since 1950s and 1960s, especially since 1970s, due to the mutual penetration of applied mathematics and groundwater dynamics, especially the popularization and application of computer technology, the content of traditional hydrogeology has been greatly enriched and broken through, and the quantitative study of groundwater has developed to a new stage. The basic theories of groundwater calculation, from steady flow to unsteady flow, from two-dimensional flow to three-dimensional flow, from analytical method to numerical solution, finite element method and finite difference method, have been widely used in groundwater resources evaluation and calculation. Through simulation calculation, the model identification and prediction are carried out, and the hydrogeological calculation problems under various conditions are solved. Computer software related to groundwater simulation calculation is improving day by day. Modflow is one of the most popular simulation software in the world in recent years, which has developed from DOS version to WINDOWS version. It has a visual interface, powerful calculation, processing and display functions, and simple operation, so it is widely used.
Many models are used in the calculation and dynamic analysis and prediction of groundwater resources, such as deterministic model and stochastic model, lumped parameter model and distributed parameter model, linear model and nonlinear model, single model and coupling model. Different regions establish corresponding models according to specific hydrogeological conditions, such as the mathematical model of multi-year balance method combined with finite element under the condition of artificial storage in Shangqiu, Henan Province; According to the dynamic evolution law of groundwater in Shiyang River basin of Gansu Province, the mathematical model and the joint mathematical model of saturated and unsaturated groundwater in yellow soil layer are established by non-standard finite difference method. Mathematical model based on elastic effect of groundwater, delayed water supply effect of groundwater and abnormal water level effect in arid and semi-arid areas. In addition, there are some special models, such as the seepage model of radioactive waste disposal site, the pollutant migration model of landfill and surface reservoir, etc.
Seven, the application of new technologies and new methods
In recent decades, measurement, testing and computer technology have developed rapidly, and have been widely used in hydrogeological investigation and research, which greatly improved the efficiency of hydrogeological work research and the quality of obtained data, and also provided a more solid foundation for understanding and explaining some hydrogeological problems.
In terms of geophysical methods, on the basis of electrical testing, various methods such as shallow high-resolution earthquake, acoustic wave, comprehensive electromagnetism, audio-frequency geoelectric field, induced polarization, very low frequency, electrostatic A card, comprehensive logging, radioactive low-energy spectrum measurement, space radio wave perspective, ultrasonic imaging and so on have been carried out. For example, shallow seismic method is used to determine the development area of underground karst, divide the Quaternary strata, ESP geological radar system is used to understand the structure and level of loose strata and the development of shallow bedrock cracks and caves, magnetic method is mainly supplemented by electric profile method, shallow temperature measurement and α card method to guide hot water wells, and audio geoelectric field method, induced polarization method and comprehensive magnetic method are used to find water, all of which have achieved good results.
In remote sensing, the application level of aerial infrared imaging scanning technology has been improved, which makes the image information richer and is beneficial to the interpretation of remote sensing images. Remote sensing method has achieved good results in finding groundwater and geothermal water, detecting ancient rivers and drawing water quality maps. In recent years, on the basis of conventional visual interpretation, the comprehensive interpretation technology of multi-variety, multi-band and multi-temporal has been further developed, which is developing towards multi-data compounding, dynamic monitoring, trend prediction and computer quantitative analysis, and many practical remote sensing geological interpretation results have been obtained.
By studying the isotopic composition of groundwater and combining with hydrogeological conditions, the source, age, runoff path and recharge relationship of groundwater can be determined, which provides scientific basis for groundwater resource evaluation, rational exploitation and prevention of groundwater disasters. According to the monitoring data of δD and δ 18O for many years, the linear equation of precipitation line in China is δD=7.7δ 18O+7.5, and the stable isotope database of precipitation in China is established and imported into the stable isotope database of precipitation hydrogen and oxygen in IAEA.
Geographic Information System (GIS) is a new technology developed in recent years, which has been rapidly applied in the field of hydrogeology. The hydrogeological spatial information of a study area can be divided into several independent information layers, and the spatial data (such as water system, water-rich zone, fault structure, control well, groundwater exploitation, hydrochemical composition, etc.). ) can be extracted in layers. GIS links the information of different layers through logical matching, generates new layers and outputs new information. At present, the software of water resources information management system based on GIS is being developed, which provides convenient conditions for digitalization and graphics of hydrogeological information.
Eight. Hydrogeological information system and its achievement display
In order to provide a large amount of hydrogeological information needed for establishing mathematical models, such as effectively using hydrogeological data, it is necessary to establish corresponding information retrieval systems and databases. Geology and mineral resources information system is a subsystem of national economic information system, including "mineral reserves database" and "groundwater resources database". Relevant databases have also been established in some parts of the country. Through the research of data management system, Henan Environmental Hydrogeology Station has developed "Henan Groundwater Resources Data Management System" and "Groundwater Balance Test Observation Data Processing System" in recent years. Shanxi Environmental Hydrogeology Station has developed "Shanxi Groundwater Dynamic Database Management System". Qinhuangdao, Shijiazhuang and Xinxiang have also established databases and database management systems respectively. They all have many processing functions such as input, change, query, counting, printing, drawing and so on.
Based on the research of information system, the expert decision-making system of urban water resources management is also studied. Through the study of information base, knowledge base and reasoning and explanation system, a general expert system for urban water resources and environment management can be established, which can realize computerization and automation, real-time analysis of water resources status, process simulation and information output, and realize the best decision-making choice.
On the display of achievements, on the basis of hydrogeological investigation data and groundwater resources evaluation, the compilation of hydrogeological maps of various scales in China has developed rapidly, creating a set of hydrogeological mapping methods with national characteristics, and compiling and publishing many national, provincial, municipal or regional maps, maps or atlases, among which the Hydrogeological Atlas of China published by 1978 basically systematically reflects the achievements of hydrogeological work in China since the 1950s. Subsequently, the hydrogeologic map of Asia (1:8 million) was compiled, as well as maps with special contents, such as the distribution map of hot springs in China (1:6 million), typical remote sensing hydrogeologic images in northern China and typical remote sensing hydrogeologic images in karst areas in China. In recent years, the digitalization of hydrogeological research results has made rapid progress, and all kinds of maps can be displayed by computer (multimedia).