What Are the Different Types of Groundwater Services?

Under the influence of natural and human factors, the groundwater level, water quantity, water quality, and water temperature change over time. More research has been done on the change of diving water level, which actually reflects the relationship between the income (supply) and expenditure (drainage) of diving aquifer water. Climate is the most active factor affecting diving dynamics.

Introduction to groundwater dynamics

Groundwater dynamics refer to changes in the groundwater level, water volume, water chemical composition, and water temperature over time under the influence of relevant factors. Groundwater dynamics provide a series of information about aquifers or systems. Groundwater dynamics are very important when verifying whether the hydrogeological conclusions made or the hydrogeological measures taken are correct. Groundwater dynamics are affected by climate, hydrology, geology, and human activities. Those affected by climate, hydrology, geology and other factors are called "groundwater dynamics affected by natural factors." dynamic".

Influencing factors of groundwater dynamics

Groundwater dynamic climate factors

Groundwater intake structure Climate is the most active factor affecting diving dynamics. In the rainy season, the infiltration of precipitation increases the diving level and the degree of diving mineralization decreases; after the rainy season, evaporation and runoff discharge gradually reduce the diving level, and valley values appear before the rainy season of the following year, and the diving mineralization increases. This cycle of changes throughout the year is called seasonal change. The secular variation of the climate will cause corresponding multi-year periodic fluctuations of the diving level.

Groundwater dynamic water body factor

Near surface water bodies, the dynamics of groundwater are significantly affected by surface water. When the river's water level rises, the diving level near the shore rises fastest, with the largest increase; away from the river bank, the change of the diving level becomes smaller, and the response time lags.

The climatic and hydrological factors determine the basic model of groundwater dynamics, while the geological factors affect the magnitude and speed of change. For example, the confined aquifer is limited by the overlying aquifer, the dynamic change of the replenishment area is strong and rapid, and the distance from the recharge area becomes weak and lagging. For diving, the greater the thickness of the aerated zone, the more water is trapped in the aerated zone, and the change in the diving level lags behind precipitation.

Groundwater dynamic human factors

Affects the natural dynamics of groundwater: For example, after drilling a well for water, some or all of the natural drainage volume will be transferred to a water production well. For another example, using surface water flood irrigation without strengthening drainage, the diving level will rise year by year due to irrigation infiltration and resupply, causing secondary swamping or salinization of the soil.

Significance of groundwater dynamics research

Studying the dynamics of groundwater is helpful to solve a series of theoretical and practical problems. Analysis of groundwater dynamics can help identify sources of recharge and identify connections between aquifers or between aquifers and surface water bodies. When determining the depth of a water well, you need to know the minimum water level to ensure water availability in dry seasons and years. To calculate groundwater resources, you must have groundwater dynamic observation data for a certain number of years. Monitoring the dynamics of groundwater under the influence of human activities can detect adverse changes early (such as salt water invading fresh aquifers and groundwater pollution) and take measures without losing time. Changes in ground stress before the earthquake can cause abnormal changes in groundwater levels and water quality. Therefore, observing the dynamics of groundwater can be used as an auxiliary method for earthquake prediction. To monitor groundwater dynamics, it is necessary to arrange representative boreholes, wells, springs, etc. to form a controlled groundwater dynamic observation network.

Groundwater dynamic equilibrium conditions

In a certain period of time in a certain area, the amount of income and expenditure related to the amount of groundwater, salt, etc. It is closely related to groundwater dynamics. The area selected for the equilibrium study is called the equilibrium area. The period of time during which equilibrium studies are conducted is called the equilibrium period. In a certain equilibrium period of a certain equilibrium area, if the income of groundwater (or salt) is greater than the expenditure, it will show an increase in storage, which is called a positive equilibrium; if the expenditure is greater than the income, the storage is reduced, which is called a negative equilibrium. From a multi-year statistical perspective, meteorological elements tend to a certain average. Therefore, the amount of groundwater storage under natural conditions also tends to a certain value, that is, it will not increase for many years. However, in a short period of time, the fluctuation of climatic factors has often caused the groundwater to be in an unbalanced state, and the amount of groundwater and the corresponding water level and water quality have changed over time. It can be seen that the dynamics of groundwater is an external manifestation of groundwater equilibrium.

In the study of equilibrium, analyze the income and expenditure terms of the groundwater equilibrium, and formulate the equilibrium equation; by measuring each known term, calculate the unknown term. The general form of the diving (volume) equilibrium equation in the natural state is in the formula, which is the inflow (outflow) amount of (downward) diving; X f, Y f are the infiltration recharge amount of precipitation (surface water); Q t is the recharge amount (Take a positive value) or cross-flow discharge (take a negative value); Q d is the diving discharge to the surface in the form of a spring or a discharge; Z c is the condensation water recharge diving; Z u is the diving surface and its adjacent capillary water Zone evaporation (including soil surface evaporation and plant emission); H is the change in diving storage at the beginning and end of the equilibrium period, where is the water supply degree, and H is the change in diving level at the beginning and end of the equilibrium period, which is positive when rising and falling Take a negative value. Under different natural conditions, the proportions of each equilibrium element in the formula are different.

Groundwater dynamic monitoring frequency

A. The time and frequency of groundwater quality monitoring, for construction projects with an evaluation level of one or two, should be sampled once during the dry and high water periods. If the evaluation work time is less than one hydrological year, a sample should be taken during the dry season. For construction projects with an evaluation level of three, sampling can be performed only once during the dry season. The groundwater quality monitoring of solid waste storage sites should be mainly carried out during the rainy season. At the same time, representative monitoring wells should be selected for dynamic monitoring of water quality and water level. For the dynamic monitoring work after the construction project is put into production, it can be used as the normal work content of the environmental protection monitoring of the construction unit, and the long-term monitoring work should be carried out according to relevant regulations.

B. The groundwater level and water volume measurement work should be completed at one time within a short period (usually 3 days) of the local dry season or peak groundwater extraction period. The peak period of groundwater extraction can be determined according to the period of centralized agricultural irrigation by local mechanical wells.

C. Long-term dynamic monitoring of groundwater levels is usually performed every 5-10 days. Observe the number of observations when there are significant changes in the water level due to special reasons (such as rainfall or accidental discharge).

D. If the prediction and evaluation of groundwater temperature is not specifically performed, the water temperature may be measured only once when the water sample is collected. If the prediction and evaluation of special water temperature is performed, the number of water temperature observations may be encrypted as appropriate.

Groundwater dynamic monitoring instrument

China Geological Survey Institute of Hydrogeological Engineering Geological Technology and Methodology has been committed to the research of groundwater monitoring technology and monitoring equipment since the 1980s. The project and key projects of the Ministry and the State Development Planning Commission's high-tech application development projects have completed the development of a variety of groundwater dynamic monitoring instruments, providing services and support for solving technical difficulties in groundwater monitoring, and providing an overall level of groundwater monitoring in China. The improvement has played a positive role.

Groundwater dynamic monitoring equipment WS1040 Tangshan Pingsheng DATA-6216 battery-powered water level monitoring equipment is designed for monitoring occasions that do not have power supply conditions, the environment is humid, and the real-time requirements of water level data are not high. This device not only solves the problem of on-site power supply, but also has low power consumption, small size, good waterproof performance, and convenient installation and maintenance.

WS-1040 Automatic Groundwater Dynamic Monitor is a new-generation groundwater dynamic monitoring instrument recently submitted by the China Geological Survey's Institute of Hydrogeological Engineering Geological Technology and Methods based on previous research results. This instrument is based on the original automatic monitoring of groundwater dynamics, and adds a GSM communication system. Through the use of the GSM global public service network, it completes the wireless transmission of data to achieve remote real-time monitoring of groundwater levels and water temperatures. The instrument can be used for groundwater level, long-term observation of water temperature, water temperature monitoring of pumping wells, surface water monitoring of rivers, lakes, reservoirs and industrial water management. Long-term automatic monitoring of dynamic changes in groundwater level and water temperature. The main body of the instrument is installed in a stainless steel cylinder, and the sensor is connected by a cable. The instrument can be put into the well, so it is easy to protect and overcome the impact of climate and weather. It is especially suitable for use in open-air observation holes. There is a storage unit inside the host, and the measured data is automatically stored in the storage unit. The monitoring data can be directly transmitted to the microcomputer through the data interface and complete the parameter setting of the instrument; Parameter setting of monitoring instrument. Its characteristics are: automatic timing monitoring, automatic storage, arbitrary setting of timing cycle; high precision, high resolution, good stability; strong anti-interference ability, unique pressure balance device ensures that the measured value of the instrument is not affected by atmospheric pressure . ^[1]

WS-1040 groundwater dynamic automatic monitoring instrument has been popularized and applied in some areas since its successful development. Practice has proved the superiority and strong field adaptability of fully automatic unattended work. In order to cooperate with the 2008 Beijing Olympic Games, 60 sets of monitoring instruments were installed and used in Beijing, which is playing a significant role in groundwater monitoring in Beijing. The monitor not only improves the scientific and technological content of the monitoring technology, but also saves human resources. It will play a positive role in optimizing the layout of the tertiary groundwater monitoring network in China.

Groundwater dynamic type

Human activities change the natural dynamics of groundwater by adding new sources of recharge or new ways of excretion.

Groundwater shock formation Under natural conditions, because climatic factors tend to a certain average state for many years, the recharge and discharge of an aquifer or aquifer system remain in balance for many years. The groundwater level, which reflects groundwater reserves, fluctuates within a certain range without continuously rising or falling. The quality of groundwater has developed in a certain direction (salinization or desalination) for many years.

Artificial groundwater extraction: After drilling groundwater or pit channels to remove groundwater, artificial mining and drainage becomes a new drainage route for groundwater; the original balance of the aquifer or water-containing system is destroyed, and some or all of the natural drainage volume is converted to artificial drainage , Natural excretion no longer exists, or the amount is reduced (spring flow, drainage flow is reduced, evaporation is weakened), and new recharge may be added.

(1) If, after a period of time, groundwater has been extracted and discharged, the new recharge amount and the reduced natural discharge amount are equal to the artificial discharge amount, and the aquifer water balance has reached a new balance. On the dynamic curve, the groundwater level is lower than before, and the annual fluctuation fluctuates, but does not continue to decrease. As shown in the example in Figure 9-6, in the Wugong area of Raoyang County, Hebei Province, Quaternary diving and shallow confined water are used as irrigation water sources. Water is irrigated from March to May (June) every year, and the water level is reduced to the lowest point. From the beginning of the rainy season in June (7), water extraction ceases, precipitation infiltration and recharge of groundwater in the surrounding area cause the water level to rise rapidly. After the rainy season, the surrounding runoff flows into the filling mining funnel, and the water level continues to rise slowly. In the early stage of water collection in the following year, the water level reached the highest point. This dynamic change shows the combined effects of natural and human factors. The dynamic type is called mining-runoff type.