Inner Mongolia-Loess Plateau Semi-arid Hydrogeological Region

This area mainly involves the middle reaches of the Yellow River including Shaanxi, Gansu, Ningxia, Inner Mongolia and other areas, including the Yinchuan Basin, Ordos Basin, Hetao Plain, Guanzhong Basin, Fenwei Basin, etc.

1. Yinchuan Plain

The Yinchuan Plain is a rift basin formed in the Cenozoic. From west to east, it consists of piedmont alluvial fan, alluvial plain, and fluvial-lacustrine plain. and the Yellow River floodplain. Loose rock pore water exists in the Quaternary sediments of the basin. The thickness of the Quaternary becomes thinner from the subsidence center to the surrounding areas, from more than 1000m to less than 500m. It is 300 to 500m in the piedmont of the Helan Mountains, and is tens of meters near the Yellow River. meters to more than 100 meters. The Quaternary loose rock single-structure phreatic aquifer in the Yinchuan Plain is mainly distributed in the western and southern parts of the plain area. It is composed of alluvial sediment at the eastern foot of Helan Mountain and alluvial sand, pebbles and gravel at the mouth of Qingtongxia Gorge. The lithology is basically the same up and down. The water is abundant and the water quality is good. Other areas are multi-layer structure aquifer distribution areas. Within a depth of about 250m, three aquifer groups can be divided. From top to bottom, they are the phreatic aquifer group (burial depth < 60m), the first pressure-bearing rock group The water-bearing rock group (burial depth 70-160m) and the second confined water-bearing rock group (burial depth 160-280m). The first and second confined water-bearing rock groups are collectively called deep groundwater. There are usually relative differences between the water-bearing rock groups. A relatively continuous aquitard layer. The first and second confined water-bearing rock groups and the single-structure phreatic aquifer are the main mining target layers.

(1) Single-structure phreatic aquifer system

The alluvial fan of the Yellow River at the Qingtongxia Gorge is a single-structure phreatic aquifer area with a single lithology, consisting of pebbles from southwest to northeast. It gradually changes to gravelly silt and fine sand, and the thickness of the aquifer changes from thin to thick, from 10m to >300m. The groundwater level is 0.5~4.0m deep, the water inflow volume in a single well is 2000m3/d, and locally it is >5000m3/d. The groundwater salinity is generally <1g/L. There is a single phreatic area in the alluvial slope plain at the eastern foot of Helan Mountain, which is 120km long from north to south and 3-10km wide from east to west. From pebbles and gravels to gravels and sand layers, the thickness of the Quaternary system can reach 500-600m. The water level at the front edge of the alluvial fan is generally 10-30m deep, and the water level at the upper part of the alluvial fan is 50-100m deep, with the maximum depth reaching 181.5m; the water inflow volume in a single well is >1000m3/d. The salinity is usually <1g/L, and the water chemistry type is bicarbonate water.

(2) Multi-layer structure phreatic-confined aquifer system

The phreatic aquifer group in the multi-layer structure area is mainly medium-fine sand, and the aquifer thickness is generally 20 to 60m , in general, the thickness of the aquifer decreases from south to north; the depth of groundwater level ranges from 2 to 10 m in the piedmont alluvial sloping plains, and is <2 m in alluvial lake plains and alluvial plains.

The burial depth of the roof of the first confined water-bearing rock group is usually between 25 and 60m, and the burial depth of the bottom floor is generally 140 and 160m. The thickness of the aquifer rock group is generally between 40 and 130m. The thickness of the aquifer is larger in the central area of ??the plain and gradually becomes thinner toward the east and west sides. It is usually composed of 2 to 5 aquifers that are hydraulically connected to each other, and they are closely hydraulically connected (Figure 2-7). The lithology of the aquifer is mainly fine sand, silty fine sand and a small amount of medium sand.

Figure 2-7 East-west hydrogeological section in the central part of Yinchuan Plain

(According to Wu Xuehua et al., 2009)

1—Sand and gravel; 2—Fine sand; 3—clay sand; 4—sand clay; 5—argillaceous sandstone; 6—sandstone; 7—limestone; 8—water level; 9—geological age and boundaries

2. Hetao Plain

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The Hetao Plain starts from the western foothills of Manhan Mountain in the east, ends in the Langshan Mountains and the Ulan Bhe Desert in the west, borders the Kubuqi Desert and the Ordos Plateau in the south, and borders the Yinshan Mountains in the north. The vast area to the west of Xishanzui is the Houtao Plain; the triangular area east of Xishanzui and west of Baotou, which is narrow in the west and wide in the east, is called the Sanhuhe Plain; and east of Baotou to Hohhot City is called the Baotou Plain. The Yellow River flows from west to east through the south side of the plain. Loose sediments with a thickness of more than 600 meters have been deposited in the plain. The deep parts are Neogene strata with high salt content. The Quaternary pore aquifer system is divided into a single-structure aquifer system and a double-structure aquifer system.

(1) Single structure aquifer system

The single structure aquifer system is mainly distributed in the piedmont of Daqing Mountain, the piedmont of Manhan Mountain, the piedmont of Wula Mountain and the piedmont of Langshan Mountain In the belt, southeastern part, and the front edge of the Ringel Platform and the northern edge of the Ordos Plateau, the sediment particles are coarse, and the clay soil is mostly distributed in a lens shape. There is no stable and continuous aquifer, forming a single-structure aquifer.

The single-structure aquifer in the piedmont of Daqingshan is composed of a series of alluvial fan groups. The upper part is mainly composed of Upper Pleistocene and Holocene gravel, sand, gravel, gravel, and sand. The general thickness is 120 ~140m, unit water inflow volume 100~500m3/d·m. Most of the single-structure aquifers in the piedmont of Manhan Mountain are Upper Pleistocene to Holocene, and the lithology of the aquifers is gravel, cobblestone, medium coarse sand, and silty fine sand. The aquifer is shallow buried, between 20 and 70m, and has a thin thickness, generally 30 to 50m. The aquifer is rich in water, with a unit water inflow of 1,000 to 32,003/d·m.

The thickness of the single structure aquifer in the piedmont of the Shetai Basin is 35 to 83 m, and the roof depth of the aquifer is 90 to 120 m. The water volume is relatively abundant, and the unit water inflow is 35 to 216 m3/d·m. The water level depth decreases from 40 to 60 m near the foothills. 10~30m of the alluvial fan skirt. The water quality is good, with salinity <0.5g/L. The lithology of the single-structure aquifer in the piedmont of Langshan and Wula Mountains is pebbly sandy gravel and gravelly medium-coarse sand. There is obvious horizontal zoning from north to south. The aquifer particles change from pebbly sandy gravel and sandy gravel to medium-coarse sand. The thickness of fine sand has changed from 50~80m to 20~40m, the water inflow has changed from 100~150m3/d to 25~100m3/d, the water level depth has changed from 20~40m to 3~5m, and the salinity has changed from <0.5g /L becomes 1~3g/L.

(2) Double-layer structure aquifer system

The double-layer structure aquifer is distributed in the central alluvial lake plain and the southern Yellow River alluvial lake plain. The lithological particles of the aquifer change from coarse to fine from north to south, with sand layers and clayey soil layers spreading between them. There is a stable, continuous, and hugely thick silty clay layer distributed among them, forming a water-proof layer. The upper part is Phreatic-slightly confined and semi-confined aquifer, the lower part of which is a confined aquifer, forming a double-layer structure aquifer. In the Hubao Plain area, the upper shallow groundwater has poor quality and is mainly used for industrial and agricultural water use; the lower confined water has excellent water quality and is used for domestic and industrial water for urban and rural residents. In the Houtao Plain, the upper shallow groundwater is mainly exploited. The lower confined water is buried deep, usually 300 to 500m and below. The water quality is poor, the water volume is small, and the mining conditions are poor. It is only found in some shallow buried areas. It is mined in small quantities and there is very little drilling data to reveal this layer.

1) Double-layer structure aquifer in the Hubao Plain:

Shallow phreatic-semi-confined aquifers are widely distributed and are upper Pleistocene to Holocene aquifers. The aquifer is buried 20 to 40m deep in the skirt area of ??the front fan of Daqingshan Mountain and east of Usutu, with a thickness of less than 20m. It gradually deepens and increases in thickness to the west, reaching a depth of 190m and a thickness of 190m in Sarqin at the west end. Also increased to 157m. The depth of the floor in the central part of the plain increases from east to west, from only 47.3m in Baimiaozi in the east to 167.6m in the west of Dacheng in the west, and the thickness increases from 34m to 101m. In the middle section of the Daqingshan Front Fan Group and the Daheihe River Valley in the east, the water inflow from a single well is mostly >10003/d. In other areas, the water inflow from a single well is mostly between 500 and 10003/d. Only in the piedmont group fan zone east of Usutu, The water inflow volume of a single well is less than 5003/d. From the northeast to the southwest in the plain area, the water inflow volume of a single well decreases from 100 to 5003/d to 50 to 1003/d, and even <503/d in some areas. The water quality is generally poor, and there is groundwater with a salinity greater than 3g/L.

The deep Quaternary confined aquifer is the lower section of the Middle Pleistocene and is widely distributed in the plain. It is only missing at the eastern edge and the rear edge of the southern platform, and is not exposed within a depth of 200-250m in the west. In the north, there are sand and pebbles mixed with gravel and gravel. To the south, the mud content gradually increases and the particles become finer (Figure 2-8). The eastern part is the ancient lakeside delta deposits of the Dahei River, which are mainly gravels. The front edge gradually becomes finer and consists of gravels, gravels and medium-coarse sands. Near the Yellow River, it is lake basin deposits. The lithology gradually changes from medium-coarse sands to fine sands, Silty fine sand, the thickness gradually decreases, and the mud content increases.

The burial depth of the roof of the Quaternary confined aquifer gradually deepens from east to west and from south to north. The deepest point is within the east-west strip of the North Shi axis-Bei Ge Du in the north of the lake basin. . It is 84m near Dongbabai, and the depth reaches 401m from the west to Beigedu. The front edge of the southern platform and the shallow lake zone in the lake basin have a slope, and its burial depth increases from 35m to 192m. To the west of Usutu, The subsidence in the piedmont zone is large, and the buried depth of the roof is between 90 and 218m. Affected by the uplift of Daqingshan Mountain and Manhanshan Mountain, the northern part is a broad shallow burial zone, with the roof burial depth ranging from 54 to 75m. The aquifer is only fully exposed in the east, with a floor depth of 107-216m, reaching a depth of 502m in the Shilamengeng-Bandingying area. The thickness of the aquifer in the eastern region is generally about 20m, and it thickens to more than 100m near Baimiaozi in the west. The thickness of the aquifer is smaller at the southern platform front and the southern edge of the shallow lakeside facies belt, with a thickness of only 10 to 32m within a depth of 200m. The ancient lakeside delta of the Dahei River in the east is the largest. The water inflow from a single well can reach more than 1000m3/d. The water inflow in the piedmont lakeside zone can also reach more than 1000m3/d. Going south to the lakeside front zone, it is 500-1000m3/d, and to the interior of the lake basin. The decrease is 100-500m3/d. In the southwest, the north bank of the Yellow River and the front edge of the lake platform, it is mostly <50m3/d. The minimum water inflow volume in a single well is less than 10m3/d. The water quality of the aquifer is generally excellent. The salinity in most areas is 0.3 to 1g/L, except for some areas in the southern and southwestern Hasuhai Sea and the northern bank of the Yellow River where the salinity is greater than 3g/L.

Figure 2-8 Goumen Town-Hejiage Du hydrogeological section in the central part of the Houbao Plain

2) Double-layer structure aquifer in the Houtao Plain:

< p>Shallow phreatic-semi-confined aquifers are distributed throughout the Houtao Plain. The lithology of the aquifers is medium fine sand, fine sand and silty fine sand from the Upper Pleistocene to Holocene, with local gravelly medium-coarse sand (Figure 2 -9).

The depth of the aquifer roof is generally less than 20m, and the thickness of the aquifer increases from 60-80m in the east to 150-240m in the west, from 20-60m in the southern uplift area to 100-200m in the north, and north of Shaanba in the west In this area, the thickness of the aquifer is the largest, and the maximum thickness revealed by drilling is 238m; the thickness of the aquifer is the thinnest in the area north of Xishanzui, generally less than 20m.

Figure 2-9 Hydrogeological profile of Dazhuangedan-Chenguang Ershe in the central part of the Houtao Plain

The burial depth of the aquifer floor increases from southeast to northwest, and the thickness in the east The thickness is 80-100m, increasing to 150-300m to the west; the thickness is 30-80m in the south, and increasing to 100-200m to the north. In the Ulan Buh Desert area, due to the influence of the Dengkou-Quansheng Xigou fault zone, the aquifer has a monoclinic structure tilting to the north-northwest. The southern aquifer floor is shallowly buried, mostly 40 to 100 meters, and the thickness is thin, generally 30~80m, heading north to the depression area at the front edge of the fan group, the floor depth is between 140~250m, and the thickness is 100~200m.

The water richness of the aquifer becomes smaller from southwest to northeast. The water inflow of a single well in the aquifer above 60m is 350~5003/d in the southwest, up to 6003/d in some places, and gradually becomes 250~3503/d and 150~2503/d, to the west side of Wuliangsuhai area, it is less than 1503/d.

The water quality of the aquifer is affected by the structure and sedimentary environment. There is more salt water in the east and fresh water in the west. The salt water and fresh water interface is consistent with the regional structure. It is roughly bounded by Yongji Canal, with upper fresh water and lower salt water to the east. Its upper and lower boundaries are roughly the boundary between the upper section ( ) and the lower section ( ) of the Upper Pleistocene; to the west it is entirely fresh water. In the central part of the plain, the depth of the salt water layer gradually increases from east to west, and the thickness of the fresh water layer gradually increases, transitioning from light salt at the top to full fresh water at the bottom. According to the results of borehole sampling analysis, the salinity ranges from 13.1 to 60.5 g/L in the southern uplift area, from 0.6 to 14.4 g/L in the northern depression area, from 0.7 to 9.4 g/L in the eastern shallow depression area, and from 0.7 to 9.4 g/L in the eastern shallow depression area. The deep depression area in the west is 0.4~9.4 g/L.

The Quaternary confined aquifer is within the exploration depth of 300m, mainly found in the area south of the Dengkou-Quanshengxigou fault zone and north of the fan skirt front fault. In the piedmont area of ??Langshan and Wula Mountains north of the fan skirt front fault, the lithology of the aquifer is mainly muddy sandy gravel and medium-fine sand, which is an alluvial-lacustrine alternating lakeside facies deposit. The roof of the aquifer gradually deepens from north to south, generally at 70-110m and 180-200m. It is fresh water. In some areas, especially in the wings and inter-fan zones of ancient alluvial fans, salt water is often distributed, with a salinity of 3 to 10g/L, the top surface of salt water is basically consistent with the upper Pleistocene floor. The water inflow volume of a single well is 500~1500m3/d. In the piedmont of Wula Mountain, the burial depth of the aquifer roof is generally 60 to 100m. There is salt water distribution to the west of Gongmiaozi, and the mineralization degree is high in some areas.

South of the Dengkou-Quanshengxigou fault zone, due to the influence of the Dengkou uplift, the aquifer is buried shallowly and becomes deeper from south to north, with the roof burial depth ranging from 60 to 100m in the south. , increases to 100~150m towards the north, and the thickness also tends to increase, but the aquifer particles become finer along this direction, changing from medium fine sand to fine sand and silty sand. The aquifer is the shallowest buried in the Dengkou area. The particles are relatively coarse, mainly medium-fine sand, with coarse sand in some parts, and the thickness is relatively large, up to 250-300m. The roof of the aquifer is 50-70m deep. The water inflow in a single well is generally 300-13003/d, all of which is fresh water. , the mineralization degree is mostly less than 1g/L, and partially 1~3g/L.

Aquifers are widely distributed on the southeast edge of the lake basin. Due to the influence of the latent uplift of Wula Mountain and the Dengkou-Quanshengxigou fault zone, the aquifers in the southern part of the plain area are shallowly buried and gradually deepen toward the north. The burial depth of the roof increases from 60 to 120m to 200m to the north. The aquifer is mainly silty and fine sand. The water volume is generally small, the salinity is more than 3g/L, and most of it is salt water. In the area near the foothills of Xishanzui, it is a lakeside facies deposit at the foothills. The aquifer particles are relatively coarse, with medium to coarse sand containing gravel. The thickness of the aquifer exposed within 200m is 12-35m, and the self-flow rate is 60-70m3/d. The water quality is still good, and the mine The chemical degree is 1-3g/L, and it has certain water supply value, but its distribution range is relatively limited. On the west side of Wuliangsuhai, the aquifer is buried deeply, with finer particles, mainly silty sand, thinner thickness, very small water volume, self-flowing, and good water quality, fresh water with a salinity of 1 to 2g/L.

The long strip on the south side of the front edge fault of the fan skirt in the center of the lake basin, from Taiyang Temple in the west to the northern end of Wuliangsuhai Sea, is structurally in the deep depression zone of the basin and is the regional sedimentation center with buried aquifers. It is very deep. The buried depth of the roof is generally 200 to 300m or less. The aquifer has fine particles, small water volume, and poor water quality, mostly salt water.

3. Fenwei Basin

The Fenwei Basin is composed of a series of Cenozoic fault basins, from north to south, Datong, Xinzhou, Taiyuan, Changzhi, Linfen, Yuncheng and Weihe River and other basins. Quaternary and Neogene Pliocene loose rock pore water-bearing rock groups are widely distributed in these basins. The basic characteristics of their aquifers vary from place to place, forming independent typical pressurized artesian basins.

(1) Datong Basin

The pore water of loose sediments in the Datong Basin is the most important aquifer group in the basin. It is mainly distributed in the alluvial fan groups in the piedmont and buried In ancient river channels, the thickness of the loose layer in depressions can reach 1000-1500m. The burial depth of the main aquifers is more than 200m, mostly 100-150m, and is dominated by middle and upper Pleistocene alluvial and alluvial sand and gravel layers (Figure 2-10).

Figure 2-10 Schematic cross-section of the pore water system in the Datong Basin

(According to Han Ying et al., 2009)

1—Aquifer; 2—Aquitard ;3—groundwater level; 4—vertical recharge; 5—vertical discharge; 6—lateral recharge; 7—aquifer age; 8—fault

The pore aquifer in the piedmont slope plain is mainly pebbles , gravel and sand layers, with a thickness of 30-80m and good water-richness. The water output of a single well is 1500-3000m3/d. The alluvial fan shaft is extremely water-rich, and the water output of a single well can reach 1×104m3/d.

The plain pore confined aquifer in the central part of the basin has a burial depth of 30 to 50m and below, and artesian wells can be seen. The artesian well in Qingquan Village, Haibeitou Township, Huairen County is 120m deep, with a water head about 5m above the surface and an artesian flow of 603 /h. The well depth at Shangqiaotou in Yijing Township, Yingxian County is 164m, the well depth at Dahuangwei Township is 480m, and the hole depth at Xingzhai Township is 230m. They are all artesian. The quality of groundwater is generally good, but in places such as Heshengbao and Dachongbao in Shanyin, the fluoride ion content is relatively high. .

The pore aquifer in the terraces of the Yuhe River Valley is a medium-coarse sand and gravel layer, and the water level is usually less than 10m deep, ranging from 4 to 10m. Large tube wells with a depth of 10 to 15m along the lower reaches of the river are found. The water volume can reach 1000~40003/d. The thickness of the confined aquifer is 20-50m, the water level is 20-60m deep, and the water output of a single well is mostly more than 1000m3/d, and the largest one reaches 5000m3/d. This area is the water source for urban and industrial centralized water supply in Datong City.

The groundwater in the Datong Basin from the edge mountains to the center has obvious hydrochemical zoning patterns, especially the horizontal zoning of phreatic water. In the piedmont sloping plain area, there is HCO3-Ca, HCO3-Ca·Mg type water, with a salinity of less than 0.5g/L. The lower part of the sloping plain and the edge of the alluvial plain transition from HCO3 type to HCO3·SO4 type, with a salinity of 0.5-1g/L. In alluvial plains, the chemical type of diving water is mainly sulfuric acid or chloride type, with a salinity of 1 to 3g/L.

(2) Xinzhou Basin

The Quaternary phreatic aquifer is composed of the Holocene and the Upper Pleistocene. The burial depth of the floor is generally 15 to 70 m, and the aquifer thickness is 7 to 50 m. From the alluvial fan axis to the inter-fan depressions, the aquifer particles gradually become finer, the single layer thickness gradually becomes thinner, and the number of layers gradually increases. In the Daying fault terrace area, the floor depth is 20-55m, and the lithology of the aquifer is mainly medium-coarse sand and gravel, with a total thickness of 7-28m; in the Daixian sag area, the floor depth is 25-92m, and the lithology of the aquifer is 25-92m. Mainly medium-coarse sand and gravel, with a total thickness of 22-34m; in the Yuanping depression area, the floor depth is 25-70m, and the lithology is mainly medium-coarse sand and medium-fine sand, with a total thickness of 25-40m; in the Qicun fault step The burial depth of the floor in the area is 15-40m, and the lithology is gravel, medium coarse sand, fine sand, etc., with a total thickness of 10-20m; in the Xinding sag, the floor is 20-55m deep, and the lithology of the aquifer is coarse-medium sand, silt, etc. Mainly fine sand, with a total thickness of 14 to 45m.

The middle aquifer is generally 46.5 to 144m deep in the piedmont slope plain area, 25 to 90m thick, and the aquifer is 10 to 40m thick. It gradually deepens from the edge of the basin to the alluvial transition zone. , the thickness of the water-bearing rock formation gradually increases. In the alluvial plain area, the floor depth is 90.6 to 158.59m, generally 100 to 140m. The aquifer and the aquifer are distributed in a sandwich shape. The thickness of the aquifer is generally 8.6 to 40m, and can reach 40 to 60m in some places.

The degree of research on deep aquifers is relatively low, and only a few boreholes reveal the Quaternary and Lower Pleistocene aquifers.

(3) Taiyuan Basin

The Quaternary pore aquifers in the Taiyuan fault depression basin are mainly Holocene phreatic water-bearing rock groups (0~50m), and the middle and upper Pleistocene pressures Water-bearing rock group (50-200m), Lower Pleistocene pressure-bearing weak water-bearing rock group (200-400m).

Shallow phreatic aquifers are distributed throughout the area. The lithology is alluvial gravel and sand, with thickness ranging from 10 to 30m. From the piedmont to the plain, the particles of the water-bearing medium change from coarse to fine, the thickness decreases, and the water-rich property becomes weaker. The water inflow volume of a single well is 500-1500m3/d, the large alluvial fan shaft can reach more than 1500m3/d, and the inter-fan depression is generally <500m3/d. The sand and pebbles and medium and coarse sand aquifers of alluvial origin in the central part of the basin are generally 5 to 25 m thick. The unit water inflow in the northern part of the Fenhe River alluvial layer is 20 to 50 m3/d·, and decreases to 5 to 10 m3/d·m in the southern part.

The medium-deep confined aquifers are alluvial and lake sediments from the middle and lower Pleistocene and upper Pleistocene, including sand, pebbles, medium sand, coarse sand and fine silt. The aquifers are mostly silt. The clay is a multi-layered pressure-bearing aquifer system with a burial depth of 50 to 200m and aquifer thickness ranging from 5 to 50m. The ancient river channels and ancient alluvial fan shafts are relatively rich in water, while the inter-fan depressions are weakly water-rich.

The Fen River alluvium to the north of the Sangui horst is highly water-rich, with a unit water inflow of 1500-5000m3/d·m. To the south of the Sangui horst, the water-rich property gradually weakens along the Fen River. In general, the unit water inflow of a single well in the area is 10-26m3. /d·m, the unit water inflow in the inter-fan depression and the alluvial layer in the south of Fenhe River is less than 2m3/d·m (Figure 2-11).

(4) Changzhi Basin

Aquifers buried deeper than 50m are shallow phreatic aquifers, and 50 to 150m (or 200m) are middle-layer confined aquifers. A large area in the middle of the basin An aquifer system with a double-layer structure; in the middle and upper part of the sloping plain, pebbles and sand layers are continuously deposited, and the sandy soil in the middle is highly permeable, making it a mixed aquifer system.

Shallow phreatic aquifers are Holocene, Upper Pleistocene alluvial, alluvial gravel and sand layers. The aquifer in the plain area has many layers and uneven thickness. Generally, the thickness of the aquifer is about 10m. There are few water-bearing layers in alluvial fans and ancient river channels of major rivers, and the single layer is thick. The sandy soil has the characteristics of water-bearing and permeable, and is generally 10 to 25 meters thick. Within the basin, there are vast alluvial lake terraces, river valley terraces, inter-fluvial blocks on both sides of the river and the center of the plain. The aquifer has become thinner and the grain size has become finer. The water richness decreases accordingly, and the unit water inflow volume of shallow wells is 5 to 10 m3/h·m or less.

Medium aquifer water is mainly distributed in river valley terraces and loess platforms. It is middle and lower Pleistocene loamy clay, clay, and loess soil. It is thick, contains few sand layers, and is unevenly distributed. At present, the mining depth is mostly 50 to 150m. The unit water inflow of boreholes with a hole depth of >100m is less than 1m3/h·m. The burial depth of the roof of the aquifer group gradually deepens from the edge of the basin to the northern center of Changzhi City, generally ranging from 0 to 50m. There is a big difference between the water richness of the aquifer and the water richness of the overlying shallow water (Figure 2-12).

Figure 2-11 Concept map of hydrogeological profile of pore water system in Taiyuan Basin

(According to Han Ying et al., 2009)

1—Aquifer; 2— Aquitard; 3—groundwater level; 4—vertical recharge; 5—vertical discharge; 6—lateral recharge; 7—aquifer age; 8—fault

Figure 2-12 Groundwater in the Changzhi Basin Schematic diagram of system profile

(According to Han Ying et al., 2009)

(5) Linfen Basin

The Quaternary loose rock pore aquifers are mainly distributed in loess Tableland area, piedmont alluvial platform, piedmont slope plain area and valley plain area.

The Quaternary aquifer in the Loess Platform Area is mainly the medium-fine sand layer of the Lower Pleistocene, which is distributed in the Emei Platform, Fenyangling-Tarshan Uplift, Qingang Uplift and the floodplain in the Huoshan Piedmont. The accumulation platform is controlled by ancient sedimentary environment and tectonic processes, and its aquifer structure also differs from place to place. The Emei Platform is a large loess platform located between the Linfen Basin and the Yuncheng Basin. The medium-fine sand layer of the Lower Pleistocene of the Quaternary System is the current main mining layer of the Emei Platform. The aquifer roof is buried deep in the low platform area. It is about 200m, and it is about 150m in the high plateau area. It has 3 to 8 layers, generally 10 to 20 m thick, and the thickest can reach more than 50 m. The medium water-rich areas are mainly distributed in the Tonghua-Jiedian Town area of ??the low plateau area and The unit water inflow in Da, Xiao Xiecun, Xuedian and other places in Gaotaiyuan District is 5 to 10m3/h·m. The unit water inflow in other areas is less than 53/h·m. The water richness is weak, and the water level is 130 to 250m deep. The permeability coefficient in medium water-rich areas is 7-9m/d, and in other areas of the plateau area, the permeability coefficient is generally less than 4m/d. The Fenyangling-Taershan loess plateau area lies across the middle of the basin. The lithology of the Lower Pleistocene aquifer of the Quaternary System is fine sand and medium fine sand. The roof is about 105m deep and the bottom is 185m deep, with 2 to 4 layers. , with a total thickness of 2~20.71m. The loess plateau of the Qingang Uplift is mainly distributed in the Xin'an-Nantang area. The lithology of the aquifer is mainly sub-sand soil, sub-clay, clay and thin layers of sandy gravel layer of the Lower Pleistocene, Middle Pleistocene and Upper Pleistocene alluvial wind. , the submersible water level is 20 to 100m deep, and the unit water inflow is less than 1m3/h·m.

The Quaternary and Lower Pleistocene (Q1) strata of the alluvial platform in the piedmont of Huoshan Mountain are 40 to 70 ? thick. The aquifer is mainly a blue-gray gravel layer with 2 to 3 layers and a single layer is 3 to 12 ? thick. , with a total thickness of 6 to 23 angstroms; the mid-Pleistocene (Q2) strata are 130 to 170 angstroms thick, and the aquifer is mainly light red and blue-gray sand and gravel, with 2 to 3 layers, a single layer is 10 to 30 angstroms thick, and the total thickness is 30 to 50 angstroms. , the water level is 90 to 100 meters deep, and the unit water inflow volume of the borehole is <13/h·m (Figure 2-13).

Figure 2-13 Schematic hydrogeological map of the piedmont of Huoshan Mountain

(According to Han Ying et al., 2009)

The alluvial fan in the piedmont of Luliang Mountain is mainly composed of It is composed of sandy gravel, sub-sand soil, sub-clay and clay in the Pleistocene and Holocene alluvial facies. In the mountainous area, the phreatic-slightly confined aquifer is Pleistocene sand and gravel, with 4 to 8 layers, a single layer thickness of 2 to 23 meters, a total thickness of ~70 meters, a floor depth of 160 to 220 meters, and a water level depth of 40 to 100 meters. , the unit water inflow volume of the borehole is 0.71~19.06m3/h·m. From the fan top to the fan edge, the lithology of the aquifer gradually changes from pebbles to coarse to medium sand to silty fine sand, with the thickness becoming thinner and the burial depth becoming shallower. In the piedmont slope plain area of ??Huoshan, Taer Mountain, Zhongtiao Mountain and Zijin Mountain on the east side, the alluvial fan is dominated by sub-sandy soil and sub-clay interbedded pebble gravel lenses, with a thickness of 30 to 100 m and a sand content ratio of 0.4 to 0.7. .

The depth of the groundwater table ranges from nearly 100m at the top of the fan to about 10m at the front edge of the fan, and the water inflow per unit borehole is 0.72 to 7.85m3/h·m.

The Quaternary sediments on the alluvial terraces of the river valleys in the middle of the basin are mainly Pleistocene fluvial and lacustrine sediments. The Lower Pleistocene aquifer is a medium-fine sand and gravel layer, with 2 to 9 layers and a thickness of 2.37~ 69.97 degrees, the roof depth is 123.87-293 degrees, and the floor depth is 240.49-402.17 degrees. It is a confined aquifer with a water level elevation of 380-505 degrees. Some areas are higher than the surface to form artesian flow. The mid-Pleistocene aquifer is composed of medium fine sand and gravel, with 2 to 7 layers, with a total thickness of 6.65 to 74.34m, a roof burial depth of 43.40 to 110.71 meters, and a bottom floor burial depth of 100.05 to 242.68 meters. It is a confined aquifer with a water level elevation of 360 to 360 meters. 440, the unit water inflow volume of the borehole is 0.1~4.32m3/h·m, and the water level is buried at a depth of 20~110. It forms an artesian flow above the surface in the area where the flood tunnel slab collapses. The pressure-bearing water head is 9.66 meters higher than the surface, which is lower than the pressure in the deep parts of the Lower Pleistocene. The hydraulic head height is 4.11°, which is the main layer for groundwater exploitation in Linfen Basin.

The Upper Pleistocene and Holocene in the river valley plain area are mainly sub-sandy soil and sub-clay in the alluvial phase of rivers and lakes interspersed with thin layers of medium-fine sand and sandy gravel. They are generally phreatic aquifers, and the floor is buried deep. 30~60m, with abundant groundwater. The spatial structure of the Lower Pleistocene, Middle Pleistocene, Upper Pleistocene and Holocene aquifers in the valley plain area and their contact relationships with the aquifers of adjacent geomorphic units are shown in Figure 2-14.

Figure 2-14 Schematic diagram of the spatial structure of the aquifer in the valley plain area

(According to Han Ying et al., 2009)

(6) Yuncheng Basin

The Quaternary aquifer in the Yuncheng Basin is distributed in the loess plateau area, loess hilly area, piedmont plain and alluvial lake plain, and its distribution and structural characteristics are different.

Upper Pleistocene-Holocene aquifer: It is a phreatic aquifer. In the Castanopsis Plateau of the Loess Plateau District, it is only distributed in the Fanqiao Station area in the northeast. The water level is 9.8m deep and the floor is 15m deep. , weakly hydrated. In the sloping plain in front of Zhongtiao Mountain, the floor of the aquifer is 27-78m deep, the water level is 2.0-40.0m deep, the total sand layer thickness is 6.28-46m, the water-bearing sand layer is 1-4 layers, and the single layer thickness is 3-34m. The soil is mainly composed of gravel and medium-coarse sand, and the edge of the alluvial fan suddenly changes to gravelly sub-clay and sub-sand soil. The burial depth of the aquifer floor in front of Jiwang Mountain is 12 to 18m, and the water level is 10 to 20m, generally 15 to 16m. The aquifer has a thickness of 1 to 5 m and is composed of medium-coarse sand. In the alluvial lake plain, the depth of the aquifer floor is 23.44-59.57m. From both sides of the valley to the center, upstream to downstream, the floor depth gradually increases. The total thickness of the sand layer is 2.0-19.0m, generally 5.0-10.0m, ranging from 1 It is composed of ~8 layers of water-bearing sand layers, with more layers 1 to 3, and the thickness of a single layer is 1.0~19.0m. In the lake swale area, the aquifer floor is buried 30 to 37 meters deep, with 1 to 2 layers of water-bearing sand. The lithology is mainly interbedded silt sand and sub-sand soil, with some parts being fine sand. In the Yellow River Stage area, the aquifer floor is buried deep. The depth is generally about 55 to 80m, with 2 to 3 layers of water-bearing sand layer, a single layer thickness of 2.0 to 30.0m, and a total thickness of 40 to 50m. There is a layer of sub-sand soil at 27-32m near the bank of the Yellow River, 3-5m thick. The upper part is a silty-fine sand layer, the lower part is a medium-fine sand layer, and the bottom of the aquifer is a medium-coarse sand layer. The upper part of other areas in the eastern part of the Yellow River bank is composed of sub-sand soil, and the lower part is composed of medium-fine sand and coarse sand.

Mid-Pleistocene aquifer: The floor depth in the Castanopsis plateau area is 142-165m, and the total thickness of the sand layer is 46-100m; it gradually thickens from west to east, and from north to south. The depth of the groundwater table is 28.0~58.0m, the aquifer has 1~3 layers, the thickness of a single layer is generally about 20m, and the lithology is mainly medium to fine sand. In the piedmont loess hilly area, the floor depth is 74-132m, the water level is 16.0-66.2m deep, the aquifer has 1-4 layers, and the single layer thickness is 1.5-30.0m, thin in the northeast and thick in the southwest. Piedmont slope plain, the floor depth is generally 122-278m, the water level depth is from 1.0-43.6m, generally 10-20m, the aquifer lithology is at the top of the alluvial fan, the axis is sandy gravel, the middle and lower parts and edges are Medium fine sand, 2 to 8 layers of aquifer, single layer thickness 0.5 to 25.0m, total thickness 0.5 to 100.0m, generally about 20m. In the alluvial lake plain area, the buried depth of the floor is generally 90 to 100 m, and gradually thickens toward the downstream alluvial lake plain. The thickness of the sand layer in the aquifer gradually thickens from the northeast to the south-west of the basin and from the valley to the alluvial plain. The lithology of the aquifer transitions from sandy gravel to silty sand and changes due to the influence of alluvial deposits in mountain ravines. In the lake swale area, the aquifer floor is 170 to 220m deep, with 2 to 11 aquifer layers. The thinnest single layer is 1.0m, and the thickest is about 10m, with a total thickness of 3.6 to 48.0m. The lithology is mainly silt sand with a small amount of fine and medium sand. In the Yellow River Stage area, the roof of the aquifer is buried to a depth of 83 to 88.7m, and the bottom is about 200m deep. The lithology is mainly medium-coarse sand, with a small amount of silty fine sand and gravel, and is about 80m thick.

Lower Pleistocene aquifer: The floor of the Castanopsis plateau aquifer is 475-497m deep, with 13-18 aquifer layers. A single layer is 3.0-27.0m thick, with a maximum thickness of 165.0m. The lithology is medium. Mainly fine sand and fine sand, with some coarse sand and silty fine sand.

In the piedmont loess hilly area, the floor depth is 310 to 400m. The aquifer in this area has 1 to 6 layers, usually 2 to 3 layers, and the thickness of a single layer is 1.0 to 20.0m. In other loess hilly areas, the floor depth is 155 to 440m, generally around 380m. Zhongtiao Mountain Piedmont is a sloping plain. The burial depth of the floor is 500m in the northeast of Wenxi Songjiazhuang. The burial depth increases due to the influence of faults in the southwest. To the north of Xia County, alluvial fan skirts are developed, and the lithology is mainly medium-fine sand and sandy gravel, with a small amount of silty fine sand. From Yuxiang to Yongji, there are 4 to 8 layers of aquifers. The thickest single layer is up to 53.0m, generally about 12m. The lithology is mainly medium-fine sand, with a small amount of gravel. The burial depth of the floor in front of Jiwang Mountain is 90 to 140m, while in the Shangwang area of ??Yuncheng, the burial depth is shallower, about 100m. The water level of the aquifer is deep in the northeast and shallow in the southwest. It is generally 50-75m near the loess hills and 30-50m in the alluvial plain. There are 1 to 3 layers of aquifer, and the thickness of a single layer is about 1.4 to 10.0m. The total thickness of the sand layer increases from the loess hills to the alluvial lake plains, ranging from several meters to 20m. In the alluvial lake plain, the aquifer has 2 to 9 layers, usually 2 to 4 layers, with a single layer thickness of 3.0 to 50.0m and a total thickness of 40.0 to 97.20m. The lithology is mainly medium to fine sand. In the lake swale area, the aquifer floor is buried 280 to 320m deep, with 1 to 4 aquifer layers, a single layer thickness of 1.1 to 12.5m, and a total thickness of 1.2 to 28.4m. The lithology is mainly medium-fine sand, with silty fine sand. .