Groundwater Protection System in Dagujia River Basin

1. Construction of groundwater protection system based on the constraint of "three red lines"

Based on the basic information of prevention and control of seawater intrusion and groundwater protection in Yantai City, with the implementation of the strictest water resources management system as the guiding ideology, with the constraints of "three red lines" (red line of water resources development and utilization, red line of water efficiency control, and red line of water function area restriction), the goal is to achieve prevention and control of seawater intrusion and sustainable utilization of groundwater, with the focus on groundwater exploitation and rational regulation of groundwater level. Adhere to the working principle of "prevention first, protection first, overall planning, comprehensive management, adapting to local conditions, highlighting key points, strict management and sustainable utilization", and adopt the management strategy of "building reservoirs in the upper reaches to control water storage, drilling wells in the middle reaches to store supplementary resources, building dams in the lower reaches to stop invasion, and multi-source joint dispatching" in Dagujia River Basin, that is, establishing a perfect early warning and forecasting system for seawater intrusion at the estuary to monitor the dynamic change process of seawater and groundwater in real time; Delineate prohibited mining areas and restricted mining areas within the scope of seawater intrusion, and effectively reduce the amount of groundwater exploitation; A large number of ground and underground seawater intrusion barrier engineering systems have been built in seawater intrusion areas, effectively cutting off seawater intrusion channels; Construction of water storage and regulation works such as tidal sluice, tidal dam, rubber dam and overflow weir in the downstream to raise the water level of the downstream river; A large number of seepage canals and wells will be built in the middle reaches of the river to strengthen the infiltration and recharge of groundwater. Carry out joint dispatching of surface water, groundwater, external water transfer, seawater and other water sources, strengthen the construction of groundwater as an alternative water source, and build a groundwater protection system. See Figure 8-5 for the framework of groundwater protection system in Dagujia River Basin.

Figure 8-5 Framework of Groundwater Protection System

2. Determination method of "three red lines" control indicators

The determination of "three red lines" control indicators (total water consumption control indicators, water use efficiency control indicators and water function area pollution control indicators) is the premise of building the most stringent water resources management system. However, at present, many areas have a certain administrative color and subjective consciousness when delineating the "three red lines" indicators, and lack a scientific and rigorous demonstration attitude. Therefore, this paper first discusses the determination method of "three red lines" control index, which provides support for the realization of joint dispatching of multiple water sources.

(1) Determination of total water consumption control index

Total water consumption control index is a control index for macro and quantitative management of total water consumption. According to the characteristics of regional water supply structure, the corresponding total water consumption control indicators are selected, including surface water consumption control indicators, groundwater consumption control indicators and external water transfer control indicators. When determining the total water consumption control index, we should first fully consider the regional surface water and groundwater resources and water supply structure, and take the available surface water and exploitable groundwater as the upper limit of the total water consumption control index; Secondly, considering the current development and utilization level of water resources and the water supply potential of alternative water source projects, following the water source construction concept of "giving priority to surface water, making full use of external water transfer, increasing the utilization of reclaimed water and compressing the exploitation of groundwater", the maximum water supply capacity of different water sources such as surface water, groundwater and external water transfer is given on the premise of considering water source replacement; Finally, combined with the local socio-economic development level and water demand, fully consider the realizability of future indicators, rationally adjust the water consumption indicators of various water sources, and formulate total water consumption control indicators that meet the requirements of different development levels.

(2) Determination of water use efficiency control index

Water use efficiency control index is a control index for fine management of regional water use behavior. When selecting water use efficiency control indicators, we can select corresponding indicators from different water use industries such as industry, agriculture and residents' life, such as water consumption per 10,000 yuan of GDP, water consumption per 10,000 yuan of industrial added value, industrial water reuse rate, average irrigation water consumption per mu, effective utilization coefficient of agricultural irrigation water, comprehensive water consumption per capita and agricultural water-saving irrigation rate. The determination method of water use efficiency control index is as follows: firstly, the current water use quota of various industries in the study area is analyzed and compared with the water use quota of the same or similar industries in the advanced water-saving areas of China; Secondly, considering the water resources conditions, water-saving level, alternative water source construction, urban residents' income and other factors in the study area, the efficiency and water-saving potential of local industries are analyzed, and the efficiency indexes such as agricultural water-saving irrigation rate, effective utilization coefficient of irrigation water, industrial water reuse rate and urban sewage reuse rate under the maximum water-saving level are determined. Finally, considering the local socio-economic development level and water resources management level, fully consider the realizability of each index in the future, make appropriate adjustments to the index, and analyze the rationality of the index.

(3) Determination of pollution control index of water functional area.

The control index of limited pollutant capacity in water functional area is the control index of quantitative management of total pollutant discharge in the region. From the point of view of water function zone management, the indicators such as the compliance rate of water intake function zone, the total amount of main pollutants entering the river, the standard discharge rate of industrial wastewater and the treatment rate of urban domestic sewage can be selected as the indicators to limit pollution acceptance. The corresponding determination methods are as follows: firstly, scientifically check the pollution capacity of water functional areas, and make clear the water quality management objectives of water functional areas on the premise of meeting the water functional requirements; Choose appropriate mathematical methods, comprehensively consider the hydrological characteristics, natural purification capacity and pollution discharge status of water functional areas, and scientifically calculate the water pollution carrying capacity. Secondly, considering the current situation of water functional areas, water pollution capacity, sewage and wastewater treatment level, pollution source layout and other factors, the pollution load reduction target is determined. Finally, the future pollution discharge level and water quality management objectives are analyzed, and the realizability of limiting pollution intake index in water functional areas is analyzed, and the indexes are adjusted appropriately and the appropriate control index values are set.

3. Determination of "three red lines" control indicators

(1) Total water consumption control index

In order to achieve the goal of groundwater pressure exploitation, it is the key to determine the scientific threshold of groundwater exploitation and groundwater level. According to the data of Cl- mass concentration and groundwater exploitation of typical monitoring wells in urban areas provided by Yantai Water Conservancy Bureau, the correlation trend line between Cl- mass concentration and exploitation and buried depth is drawn. Considering the representativeness and completeness of the data, the determination of Cl- mass concentration in this study is mainly based on the observation data of Gongjiadao water source monitoring station of Yantai Power Plant, and calculated with reference to the observation data of Jiahe Chicken Farm in Yantai City and the water source monitoring station in the south upper part of Yantai Power Plant.

Through the analysis of the historical monitoring data of Yantai City, it can be seen that the overall change trend of Cl- mass concentration in groundwater and exploitation amount is: Cl- mass concentration increases with the increase of exploitation amount, while Cl- mass concentration decreases with the decrease of exploitation amount, indicating that the Cl- mass concentration in groundwater in this area is controlled by groundwater exploitation amount, as shown in Figure 8-6.

To sum up, only by establishing the relationship equation between the mass concentration of Cl- in groundwater and the exploitation amount and groundwater level can the mass concentration of Cl- in groundwater under different exploitation conditions be predicted. The relationship equations between the mass concentration of Cl- in groundwater in Dagujia River Basin and regional exploitation (Q) and buried depth (H) are shown in Formula (8-9) and Formula (8- 10).

ρ(Cl-)= 2 13. 16 1n(Q)- 17 18.5(8-9)

ρ(Cl-)= 139.27 1n(Q)-25.542(8- 10)

Combined with the expression of the relationship between seawater intrusion and groundwater, according to the general judgment standard of seawater intrusion, seawater intrusion will occur when ρ (Cl-) > 250 mg/L/L. According to formula (8- 1), when ρ (Cl-) = 250 mg/L, the corresponding exploitation amount is 654.38+0024800 m3. According to the latest total water consumption control index from 20 1 1 to 20 15 in Yantai, the controlled groundwater exploitation in Yantai is 12 1 10,000 m3, which is basically consistent with the predicted groundwater exploitation control threshold, and also shows that the prediction result is reasonable. On the premise that seawater intrusion can be controlled, further consideration should be given to gradually restoring the virtuous circle of groundwater system to reach the pre-invasion balance as much as possible. Considering the groundwater system of the whole city, the corresponding exploitation amount of Gongjiadao Water Source Monitoring Station of Yantai Power Plant is 81000000 m3, which is taken as the control index of groundwater exploitation amount for seawater intrusion prevention in 20 15 years.

Figure 8-6 Relationship between Chloride Ion Concentration in Groundwater and Exploitation Amount and Buried Depth

According to Yantai 20 1 1 ~ 20 15 Annual Water Consumption Control Index, the annual water consumption control index includes local surface water control index, groundwater control index and regional external water control index, that is, the maximum allowable water consumption index of the year. It is stipulated that the control index of surface water consumption in Yantai city in recent years is 295 million m3, and the diversion water is 465,438+600,000 m3. Combined with the above calculation results of groundwater exploitation threshold, the groundwater control target is 8 1 10,000 m3 and the total water consumption control index is 417.5 million m3, as shown in Table 8- 10.

Table 8- 10 Annual Total Water Consumption Control Index of the Lower Reaches of Dagujia River Basin in Planning Level

(2) Water use efficiency control index

According to the general requirements of the strictest water resources management system, Yantai City has compiled a water use efficiency control index of 20 1 1 to 20 15 with the goal of improving water use efficiency, curbing water waste, promoting sustainable water use and supporting sustainable economic and social development. Recent Downstream of Dagujia River Basin (20 15)

Table 8- 1 1 Annual Water Use Efficiency Control Index of the Lower Reaches of Dagujia River in Planning Level

(3) Pollution control index of water functional area

In recent years, with the rapid development of industry and the promotion of urbanization, the discharge of wastewater is increasing, and the amount of pollutants entering rivers is also increasing, which greatly exceeds the carrying capacity of water environment, resulting in water pollution and serious deterioration of water quality in some areas. The decline of water function and the decrease of available water resources caused by water pollution make the already severe contradiction between supply and demand of water resources more prominent. In order to further promote the smooth implementation of the strictest water resources management system, strictly control the total amount of sewage discharged into the river, and ensure the safety of water ecological environment, the Water Resources Department of Shandong Province has formulated the Pollution Acceptance Control Index of Water Function Zones in Shandong Province (Provisional), 201,according to the Comprehensive Water Resources Planning and Water Function Zoning of Shandong Province approved by the provincial government, and according to the Opinions on Total Pollutant Discharge Control of Water Function Zones in Shandong Province.

Table 8- 12 Pollution Control Index of Water Function Zone in Dagujia River Basin in 20 15 Planning Level Year

4. Groundwater protection measures in the lower reaches of Dagujia River Basin

Combined with the "Twelfth Five-Year" water conservancy planning of Yantai City and the water conservancy project construction to be carried out in the near future, the groundwater protection measures in the lower reaches of Dagujia River Basin are further put forward, including the overall layout and management measures system of the engineering measures system.

(1) groundwater protection engineering measures

In view of the tongue-shaped seawater intrusion in Yantai City, we can adopt the control strategy of "building a reservoir in the upper reaches to regulate water storage, drilling wells in the middle reaches to intercept and replenish water sources, damming downstream to intercept and prevent intrusion, and multi-source joint dispatching". Urban groundwater protection engineering system specifically includes surface reservoir engineering, underground reservoir engineering, water body replacement engineering, river pollution interception engineering, regional water regulation engineering, alternative water source engineering and other water source development and groundwater protection engineering. Groundwater protection engineering measures are as follows:

1) build a reservoir at the estuary and block the passage. According to the local hydrogeological conditions, surface and underground reservoirs were built at the estuary to prevent seawater intrusion and store underground fresh water.

2) cascade water storage, strengthen the supply. In the middle and lower reaches of rivers entering the sea, cascade dams will be built, seepage canals and wells will be excavated, and artificial wetlands will be built to accumulate fresh water entering the sea in the river and strengthen the infiltration and recharge of groundwater.

3) Water source replacement, well sealing and pressure production. By diverting surface water from the reservoir to replace the groundwater source in the invaded area, a large number of unconventional water source utilization projects such as rainwater storage projects and seawater utilization projects are developed. On this basis, the well is closed and pressure mining is vigorously carried out to restore the groundwater level in the estuary.

4) Regional water transfer to increase water supply. With the construction and implementation of the Yellow River Diversion Project in Jiaodong area, the effect of reducing or preventing seawater intrusion can be achieved by strengthening the reservoir of the diversion project and optimizing the water supply pipe network of the water plant.

(2) Groundwater protection and management measures

The degree of seawater intrusion is closely related to man-made exploitation of groundwater, and over-exploitation of groundwater is the main reason for seawater intrusion. Therefore, local governments and relevant parties should formulate or improve laws, regulations and supporting systems for groundwater management and protection as soon as possible, strictly examine and approve groundwater intake permits, strengthen the supervision of water intake measurement, and adjust the layout of groundwater exploitation in a planned way; At the same time, strengthen the basic work of groundwater, including building groundwater monitoring network to monitor seawater intrusion, formulating reasonable water price mechanism, establishing groundwater management model and other related work, and fully implement groundwater management and protection.

1) Define the total control index of urban water consumption and strictly implement water intake management.

2) Establish an early warning line of groundwater level, dynamically monitor the exploitation of groundwater resources, and limit over-exploitation.

3) Define the surface water functional area to limit the pollution capacity, establish the early warning line of the pollution capacity of the water functional area, increase the scale of sewage treatment and reuse, and protect the water environment.

4) Vigorously promote the construction of water-saving society and the level of water demand management, and improve the efficiency and benefit of water use.

5) Establish and improve the water resources management information and decision-making system, and realize the automatic and unified dispatching of urban multi-water joint water supply.

To sum up, Dagujia River is a seasonal river. The flood season is from June to September every year, and the runoff accounts for 84% of the annual runoff. A large number of water resources are not used and flow into the sea. Inter-annual changes are also great. The maximum annual runoff occurred at 1964, which was 564.96 million m3, and the minimum annual runoff occurred at 1999, which was 0,000 m3 in 2000. Moreover, Dagujia River passes through Haiyang, Rushan, Qixia, Mu Ping, Fushan, Laishan, Zhifu District and Development Zone, so the joint operation of Dagujia River water resources needs to overcome time and regional problems. In order to give full play to the regulation function of underground reservoirs and improve the utilization rate of water resources, Jiahe River Basin vigorously develops agricultural water-saving irrigation and urban efficient water use, and vigorously builds water conservancy facilities in Jiahe River Basin to realize the cascade development of water resources and the protection of groundwater resources, so as to realize the efficient joint utilization of surface water and groundwater in space. The efficient utilization mode of water resources in Dagujia River Basin is shown in Figure 8-7.

Figure 8-7 Efficient Utilization Mode of Water Resources in Dagujia River Basin