Groundwater system in Daxinganling area

Daxinganling area can be divided into Quaternary pore phreatic water-bearing system, fracture-pore water-bearing system, bedrock fissure water-bearing system and permafrost zone water-bearing system.

Pore phreatic water-bearing system of Quaternary loose rocks

The water-bearing system is linearly distributed in the valleys and valleys of Daxing 'anling. The main valleys are Hailaer River, Genhe River, Ergon River, Ganhe River, Nuo Min River, Arun River, Yarlung Zangbo River, Chuo 'er River, Taoer River, Huolin River, Wulijimuren River, Xilamulun River and Laoha River. The lithology of the aquifer is Holocene alluvial-diluvial sand, gravel and pebble layers in the upper part, and clay gravel layers accumulated by middle-upper Pleistocene moraine and ice water in the lower part, basically without aquifuge, forming a unified water-bearing body. Generally, the river valley is wide, with the middle and lower reaches 2 ~ 5 km wide, reaching 10km locally. The aquifer is thick, with an upstream thickness of 20 ~ 30m and a downstream thickness of 30 ~ 40m. From upstream to downstream, the aquifer particles gradually become finer and the water content becomes better. The unit water inflow of the upstream gullies is100 ~ 300m3/d m or 300 ~ 500m3/d m; Downstream large and medium-sized river valleys, with a unit water inflow of 500 ~ 3000m3/d m, are rich in water and are the main water supply sources.

The surface water system in this area is developed and the surface water resources are abundant. Runoff of each river is above 2× 108m3/a, generally (4 ~ 10 )× 108m3/a, Nuo Min River is 42.89× 108m3/a, and the main river is 33.83× 008m3. After groundwater exploitation, a large amount of surface water leakage can be replenished, and the water storage capacity is strong, so it is the most abundant diving area.

Secondly, fracture-pore water-bearing system.

Fracture-pore water-bearing system is mainly distributed in Mesozoic and Cenozoic fault basins such as Bayan Basin and Huolinhe Basin in Ewenke Township, Molidawa Daur Autonomous Banner.

Bayan basin is a NNE syncline basin, and the aquifer is composed of Cretaceous sandstone and glutenite. Its sedimentary feature is that the thickness increases from the edge of the basin to the center of the basin, and the maximum thickness can reach 200m·m m. Because of the different aquifer thickness, particle size and cementation degree, the water abundance of different sections is obviously different. The depression on the west side of the basin is deep, the aquifer has coarse lithologic particles, and the water level is shallow, generally about 5m. The water inflow is large, and the unit water inflow can reach 250 ~ 300m3/d m, while the lithology on the east side of the basin has little change, the particles are fine, the content of cohesive soil increases, the buried depth of groundwater level increases to 70m, and the water inflow is smaller than that in the west, and the unit water inflow is 100 ~ 65440. ..

Huolinhe basin is a faulted basin. The aquifer is Cretaceous sandstone and glutenite with poor cementation, developed cracks and pores and good water permeability. The aquifer thickness is 10~50m in the south, slightly larger in the north, and the buried depth of water level is less than 10 ~ 50m. The abundance of water resources in the basin is quite different, and the unit water inflow at the edge and south of the basin is less than 25m3/d m, and the abundance of local water resources is poor. The unit water inflow in the middle of the basin is 250 ~ 500m3/d m, and the water yield is good. The southern part of the basin is confined water area, with the water head higher than the surface 1 ~ 5m, and the unit water inflow less than 25m3/d m, so the water abundance becomes worse.

Three, bedrock fracture water-bearing system

The bedrock in this area is widely distributed, with developed fractures, deep valleys, developed water systems and wide river valleys. The bedrock fissure water is mainly phreatic water, and the aquifer is weathered fissure zone. Water abundance is closely related to the degree of fracture development. From east to west, the degree of fracture development is weakened and the aquifer thickness is relatively thin. Generally, the fracture development depth is 10~30m ~ 30m, and the groundwater runoff modulus is (2 ~ 3) ×104m3/km2 a.

Gullies are developed in this area, with more precipitation and better water circulation conditions. Leaching is the main method, and the chemical types of groundwater are mainly calcium bicarbonate and HCO calcium and magnesium, followed by HCO calcium and sodium. The salinity is low, mostly less than 0.5g/L, and the water quality is good. However, in some valleys and depressions, the fluorine content is relatively high, generally1~ 2mg/L, and locally above 3mg/L. ..

Four, permafrost zone water-bearing system

The northern part of this area is tundra, with an annual average temperature of -3 ~-5℃ and permafrost distribution. The northern region is a continuous permafrost distribution zone with a lower limit of more than 60m, and the seasonal melting zone is 0.5 ~ 2.5m The southern region is an island permafrost distribution zone with intermittent permafrost distribution. The upper limit of frozen layer is about 8m, the thickness of frozen layer in the north is relatively large, generally about 70m, and it gradually becomes thinner to 5 ~ 20m in the south.

The northern melting zone is small and the connectivity is poor; The southern melting zone has a large area and good connectivity. The groundwater volume in frozen area changes greatly, and the unit inflow can be increased from less than 25m3/d m to1000m3/d m.

There is fissure confined water under the frozen soil layer, and the confined water head is higher than the ground in some areas, forming self-flow, and the water quantity is small, and the general unit water inflow is less than100 m3/d m.