I. Background

Groundwater is a vital freshwater resource on Earth, widely used for industrial, agricultural, and domestic water supply. However, in recent years, uncontrolled extraction has led to a decrease in groundwater volume and a drop in water levels. Concurrently, the discharge of industrial and domestic wastewater has degraded groundwater quality, causing issues such as land subsidence and ecological degradation. Traditional groundwater monitoring methods struggle to predict water quality trends and future pollution changes, limiting the rational development and utilization of groundwater.

Groundwater resources are more complex than surface water resources. Changes in the quality and quantity of groundwater itself, the environmental conditions causing these changes, and the laws governing groundwater movement cannot be directly observed. Furthermore, groundwater pollution and land subsidence caused by groundwater over-extraction are slowly evolving processes. Once they accumulate to a certain extent, they become irreversible damage. Therefore, accurate development and protection of groundwater must rely on long-term monitoring to grasp the dynamic changes promptly.

II. Current Situation Analysis

The collection of groundwater level data can not only identify, analyze, and resolve problems promptly and accurately, thereby guiding practical work, but it also serves as crucial evidence for studying the dynamic patterns of groundwater levels and understanding the characteristics of groundwater level changes in different hydrogeological units, different strata, and different water sources. It is of great significance for water resource research and management.

Groundwater monitoring refers to the observation of changes over time and space in groundwater levels, volume, quality, pressure, temperature, flow velocity, flow direction, etc., under the influence of natural or anthropogenic factors. Groundwater monitoring should be conducted purposefully, planfully, and systematically based on the needs of geotechnical engineering and structural stability.

Currently, groundwater monitoring faces numerous challenges. On one hand, some monitoring points are located in remote areas with power supply difficulties, relying on solar panels, and the equipment requires independence, scalability, and integration stability. On the other hand, the selection and configuration of monitoring equipment should be based on specific monitoring needs and site conditions, considering various factors comprehensively. Furthermore, the performance of monitoring equipment and the quality of data also vary, necessitating strengthened quality supervision of equipment and data management.

III. Solution Approach

To address the challenges of groundwater monitoring, the following approaches can be adopted:

Optimize Equipment Selection and Configuration: Reasonably select monitoring equipment based on factors such as monitoring objectives, site conditions, and budget, ensuring its adaptability and reliability.

Strengthen Equipment Quality Supervision: Establish strict quality standards and certification systems, and enhance supervision over the production, installation, and operation of equipment to ensure the accuracy and reliability of monitoring data.

Improve Data Management and Application: Build professional data management platforms for the centralized storage, organization, and analysis of monitoring data, mining data value to provide scientific basis for groundwater management and protection.

Enhance Technical R&D and Innovation: Continuously invest in R&D resources, promote the upgrading of monitoring technologies, and improve equipment performance and intelligence levels, such as developing more efficient sensors and data transmission technologies.

IV. System Composition and Equipment Selection

The groundwater monitoring system primarily consists of the following components:

1.Water level monitoring equipment: Such as integrated water level and temperature loggers, pressure-based water level gauges, etc., used to measure changes in groundwater levels and suitable for different measuring ranges and accuracy requirements.

Integrated Water Level and Temperature Logger:

The water level and temperature logger is used to measure the water level and temperature in wells. The measured data is transmitted to a telemetry terminal unit via signal cable.

The logger contains built-in pressure and temperature sensitive elements. Utilizing the piezoresistive effect, it converts the applied hydraulic pressure into an electrical signal. This electrical signal is then transformed into an RS485 standard long-distance transmission signal by a voltage-current converter.

Calculation formula: P = PI + Q * H

Where:
P: Measured liquid pressure
PI: Atmospheric pressure
H: Liquid depth
Q: Specific gravity of the measured liquid

Since atmospheric pressure varies with geographical elevation, a vented cable is used with the sensor to introduce atmospheric pressure (PI) to the other side of the sensitive element. The vent hole in the cable connects to the atmosphere. This modifies the calculation formula to: P = Q * H

Thus, measurement errors caused by changes in atmospheric pressure are eliminated, achieving a measurement accuracy of up to 0.05%.

For water level measurement in pools with significant fluctuations, methods such as anti-wave tubes or fixed brackets can be employed to secure the transmitter based on the specific situation.

2.Water Quality Monitoring Equipment: This includes multi-parameter water quality analyzers and water samplers. These devices can monitor parameters such as pH, conductivity, dissolved oxygen, and heavy metal content, meeting diverse water quality monitoring requirements.

3.Data Acquisition and Transmission Equipment: Such as data loggers and telemetry terminal units, are responsible for collecting sensor data and transmitting it to the monitoring center via wired or wireless communication methods, ensuring the timeliness and integrity of the data.

IV. System Composition and Equipment Selection

4. Remote Monitoring and Management Platform: Composed of servers, monitoring software, and other components, it enables the reception, storage, display, and analysis of monitoring data, supports remote device management and control, and enhances the operational efficiency and management level of the monitoring system.

Data Acquisition Section: The data acquisition section consists of water level sensors, water temperature sensors, pH sensors, conductivity sensors, turbidity sensors, and other groundwater monitoring sensors, which collect data on groundwater quality.

Network Transmission Section: The primary equipment in the network transmission section is the intelligent telemetry terminal unit. It is responsible for connecting to the front-end acquisition devices and transmitting the collected data via 4G wireless networks or other networks.

Data Management Center: The data management center can be further divided into three sub-sections: the Water Resources Monitoring Cloud Platform, the Data Processing Center, and the Database Storage. The Water Resources Monitoring Cloud Platform can be a dedicated platform or a user-developed cloud platform for water resources monitoring. It visualizes and processes the data through large screens, PCs, and mobile devices, while simultaneously storing the data in a database for permanent retention.

The groundwater online monitoring system utilizes modern sensor technology, Internet of Things (IoT) technology, and mobile communication technology to conduct real-time monitoring of groundwater parameters such as pH, water temperature, dissolved oxygen, turbidity, conductivity, water level, ammonia nitrogen, and chloride. Data is transmitted in real-time to the monitoring center platform via hydraulic telemetry terminals. The platform automatically receives and stores the data and analyzes the patterns of groundwater changes. The system employs solar power or lithium battery self-power supply, conserving energy.

In terms of equipment selection, factors such as measurement range, accuracy, stability, environmental adaptability, and cost must be comprehensively considered to ensure the performance and reliability of the monitoring system.

V. Application Scenarios

1. Urban Water Supply Source Monitoring: Install groundwater monitoring equipment at urban water supply sources to monitor water level and quality changes in real-time, ensuring the safety of the water supply. If any abnormal water quality is detected, measures can be taken promptly to prevent contaminated water from entering the supply system.

2. Industrial Contaminated Site Monitoring: Conduct long-term monitoring of groundwater around industrial contaminated sites to assess the spread and impact range of pollutants, providing a basis for pollution remediation and risk prevention and control. Monitoring data guides the implementation of remediation projects, reducing costs and improving effectiveness.

3. Agricultural Irrigation Area Monitoring: Monitor groundwater levels and quality in agricultural irrigation areas to rationally arrange irrigation water use and prevent over-extraction and water quality pollution. Optimize irrigation schedules based on monitoring data, improve water resource use efficiency, and ensure sustainable agricultural development.

Through the above measures, the efficiency and quality of groundwater monitoring can be effectively enhanced, providing strong support for the rational development, utilization, and protection of groundwater, and ensuring the sustainable use of groundwater resources.

VI. Watersurvey Project Case

Tangshan Groundwater Monitoring Project