(2) groundwater movement law in the lower reaches of Wanghe River
(1) power supply
The groundwater in this area is mainly replenished by atmospheric precipitation, followed by river runoff and lateral seepage of bedrock fissure water. Due to the continuous drought in the early stage in recent years, precipitation is less, rivers are cut off, and groundwater recharge is seriously insufficient.
(2) Excretion
The drainage form of groundwater in this area is mainly artificial exploitation, and a small amount evaporates during migration. With the increase of exploitation and the sharp drop of groundwater level, a large area of negative funnel area has been formed in this area. It can be seen from the contour map that the lowest elevation of water level has reached-18.0m, and the serious imbalance of recharge relationship has accelerated the inland movement of seawater. Groundwater flows from southeast to northwest, and some areas are affected by mining, and the water flows to concentrated mining areas. Near Yinjia in the negative funnel area of the lower reaches of Wanghe River, groundwater flows from SW to NE and then from NW to SE in the negative funnel area, reflecting the direction of seawater intrusion into groundwater.
2. Dynamic analysis of groundwater
The main recharge source of regional groundwater is atmospheric precipitation. According to the relationship curve between the average water level and precipitation for many years in this area and the water level map of June and September of 1990, the groundwater level dropped greatly before the flood season due to the large amount of groundwater exploitation. A large funnel area is formed near Houlu Village and Qiandeng Village, with the maximum depth of-15.0 ~ 18.0 m. By the end of the flood season, the groundwater level is replenished by atmospheric precipitation and river runoff, and the water level rises obviously, and the water level changes slightly behind the rainfall, and the change law is basically the same. High water level usually occurs from July to 10, and its peak value depends on precipitation. The low water level usually appears from April to June every year, and its valley value is controlled by the rainfall in the previous year and the amount of industrial and agricultural exploitation.
The dynamic change of groundwater level also depends on river runoff. Wanghe River is a seasonal river. During the flood season, the river surged and plummeted, and it was discharged into Bohai Bay in the form of surface runoff, and it was cut off for a long time during the dry season. River runoff depends on annual rainfall, duration and rainfall intensity. The greater the annual rainfall, the longer the duration, the more uniform the rainfall intensity and the greater the river runoff, and vice versa.
The dynamic law of regional groundwater is strictly controlled by atmospheric precipitation, and the annual and inter-annual distribution is extremely uneven. In the dry season, the groundwater level drops, and in the rainy season, it rises. In the continuous dry season, the groundwater level drops greatly, and in the feng shui year, it rises greatly. This reflects that the aquifer in this area has good permeability and connectivity, and the hydraulic connection between surface water and groundwater is close.
After the courtyard sluice was built in the middle and lower reaches of this area, the infiltration time of surface water into groundwater was increased. Comparing the isobar graphs before the sluice was built1June 1994 and after the sluice was built1February 1995, it is found that the negative values in the isobar graphs of the lower reaches of Wanghe River1June 1994 are connected, with a large area, while the negative values range from1June 1995 to 65438.2. However, the negative area far away from Wanghe River has also narrowed, and the water level has slightly increased. After the completion of Pinglidian Sluice, the water levels in Zhu Feng and Wang Jia increased obviously. In addition, the construction of recharge project can effectively increase the infiltration intensity of surface water and make it fully converted into groundwater. 199 1, the Chinese academy of sciences has done experiments in this field, and the effect is good.
After the completion of the underground reservoir, with the change of groundwater flow field, on the one hand, it can prevent seawater intrusion and improve water quality, on the other hand, it can give full play to the regulation function of the underground reservoir for many years, so as to achieve the purpose of making up for the regret with abundant resources, making up for fixed mining and balancing mining.
3. Physical and chemical characteristics of groundwater
Due to the over-exploitation of groundwater in this area, a negative funnel area was formed, which led to seawater intrusion and the physical and chemical properties of groundwater changed greatly. Generally speaking, the hydrochemical types of groundwater in this area can be divided into four types, namely -Cl- type water, Cl- type water,
S
O -Cl water, Cl water.
According to the Standard for Drinking Water (GB 5479-85), the toxicological and bacteriological indexes of the two groups of water samples meet the standard, and the sensory indexes basically meet the standard. Except for pH value, iron, manganese, copper, zinc, volatile phenol and anionic synthetic detergent, the general chemical indexes are basically up to standard, and the total hardness, sulfate, chloride and total dissolved solids all exceed the standard 1 ~ 3 times. After the completion of the underground reservoir, with the change of groundwater flow field, the water quality will gradually improve.
4. Hydrogeological zoning
According to the genetic types of groundwater, this area can be divided into three hydrogeological areas, namely Quaternary pore phreatic area, shallow freshwater-free area and bedrock fissure water area.
(1) Quaternary pore phreatic area (Area I)
This area is distributed in the south-central part of the rain reservoir, and the water inflow of single well on the shore can divide this area into three sub-areas.
I 1 area: the water inflow of single well in this area is greater than 1000m3/d, which belongs to strong water-bearing area and is widely distributed in the alluvial-diluvial plain of Shabuzhuang-Guoxi Town-Yuanshangwang River West. The aquifer in this area is composed of Quaternary Holocene alluvium, Pliocene alluvium gravelly coarse sand and gravelly coarse sand with a small amount of soil, with a thickness of 6 ~ 20m, and the water inflow of a single well is generally 1 0,000 ~11,600m3/d, with abundant water. The sand layer in the north of this area is banded, and the water inflow of a single well changes greatly.
I2 area: The water inflow of single well in this area is 500 ~ 1000m3/d, which belongs to medium water-bearing area and is distributed in the flood plain of Youzhu Town-Zhangjia-Panjia-Qiandeng-Jiexi and Xiyou Town. The aquifer in this area is composed of gravelly coarse sand and gravelly coarse sand with a small amount of soil, which is Quaternary Holocene alluvial deposit and Pliocene alluvial deposit, with a thickness of 2 ~ 10m and a single well water inflow of 450 ~ 965m3/d. ..
I3 area: The water inflow of single well in this area is generally less than 500m3/d, which belongs to weak water-bearing area and is distributed in alluvial-diluvial plain in Jiazheng-Lujia-Jony J area. The aquifer in this area is mainly composed of gravelly coarse sand and gravelly coarse sand with a small amount of soil, which is Quaternary Holocene alluvial and Pliocene alluvial and diluvial deposits. The thickness is generally less than 5m, and the water inflow of a single well is generally 200 ~ 480m3/d. ..
(2) Shallow water area without fresh water (Area II)
According to the nature of the aquifer, the groundwater type is still Quaternary pore phreatic water, which is distributed in the coastal plain north of Zhu Youzhen-JOE-Cuijia and Cangshang-Danshan-Shaling. Due to the influence of seawater intrusion, groundwater in this area has been salinized, TDS is generally greater than 3g/L, and Cl- content is generally greater than 1000mg/L, which can no longer meet the needs of water supply for industrial and agricultural production, and most of the original water intake wells have been abandoned. The aquifer in this area is mainly composed of gravelly coarse sand and gravelly sand deposited by Quaternary Holocene marine, gravelly coarse sand and gravelly coarse sand deposited by Quaternary Pleistocene flood, with large thickness and abundant water. For example, in the west of the reservoir area and the northeast of the warehouse soil, the thickness of the sand layer can reach 7.90 ~ 13.30m, and the water inflow of a single well is generally greater than1000m3/d; The aquifer in the north of the single mountain is relatively thin, generally 4.0~4.5m, and the water inflow of a single well is about 500m3/d. ..
(3) bedrock fissure water area (Zone III)
Bedrock fissure water is mainly distributed in the eastern hills and residual hills of the reservoir area, the metamorphic rocks of Minshan Formation in Sanshandao and Cangshang, and the weathering cracks and structural cracks of granite and granodiorite in the late Yanshan period. Due to the comprehensive influence of different factors, such as structural location, weathering degree of coal bunker, development degree of structural cracks, burial conditions, etc., the water inflow of a single well changes greatly, but it is generally less than 100 m3/d, which is a very weak water-bearing area.