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Features of geological structure, hydrogeological riparian zone from Son Tay town to Hung Yen

Complete the research area of the town from Shanxi to Hung Yen is covered with Quaternary sediments in which two strips along the edge adjacent to the edge of the northern plains is ancient alluvial plain. Red River coastal alluvial plain young Quaternary sediments study area was divided into 9 units with different age and origin including Lizhi Formation Early Pleistocene age, the age of the Pleistocene formations Hanoi mid - late, formation late Pleistocene age, Vinh Phuc, Hai Hung formation early Holocene age - middle age formations Pacific late Holocene.

Based on lithological composition of rocks containing water, geological structure and characteristics of their water division conducting hydro-geological cross section into two aquifers holes and cracks aquifer 1.

Aquifer vulnerability Holocene sediments (qh)

Describe aquifer exposed on the surface of the area of research, particularly riparian strips. Lithological composition usually divided into two classes. Distribution layer on discontinuous include loam, sandy upper part of the formation of the Pacific have a very small thickness of approximately 10 meters. Rock has low water permeability, hydraulic conductivity ranges from 0.0036 to 0,065m / ng. The lower layer of sand with different particle size mixed with gravel, the average thickness of about 10 m. Conductivity coefficient of soil water storage changes from 20 to 800 m 2 / day. Water release gravity coefficients ranged from 0.01 to 0.17.

Depth of ground water level is usually 3 to 4 meters, in separate inner suburbs of Hanoi is lowered to 10 meters deep water exploitation by the powerful is happening here in the aquifer below makes the water level is lowered according qh floor. Qh floor groundwater mainly no pressure, where the pressure is only by rare geological structures so tiny.

Aquifer vulnerability Pleistocene sediments (qp)

Aquifer described widely distributed area of ​​research, but did not disclose on the ground that was just caught by the borehole. Depth caught aquifer roof usually from 10 meters in the northwest to 35 meters in the center and southeast of the study area.

Composition of rock containing water is usually divided into two classes. Class on medium to coarse grained sand is mixed with gravel under the lower part of the formation of Vinh Phuc has a thickness of 10 meters to 15 meters. The bottom layer consists of pebbles, gravel, sand thickness of 10 meters and 35 hotels meter. Conductivity coefficient (KM) of the upper layer of rock containing water is 50-300m 2 / day, the bottom layer 300-1600m 2 / day, sometimes larger. Groundwater pressure, the pressure column typically 10-23m. Ink pressure usually distributed at a depth of 2-4 m above the ground, the inner city areas of Hanoi by water extraction is very strong on this floor so the water level lowered to 10-30 meters deep.

Qp aquifer which is very rich in water, almost all experimental bores are larger flow rate 1 l / sm, 70% of boreholes experiment flow rate greater than 3 l / sm Water in qp floor is fresh water, total mineralization of up to only 0.8 g / l with mainly Bicarbonate ingredients - calcium, sometimes where Bicarbonate chloride - calcium.

Located between 2 aquifer sediments above the water way Formation Hai Hung and Vinh Phuc, water sediments above only way out at the edge of the plain, and in the study area being covered. But along the Red River, especially the section from Shanxi to the end of the urban area of ​​Hanoi, making them eroded and qp qh aquifer directly upon each other to form the geological windows Posted make Red river water and the qh aquifer and hydraulic qp relationship tightly in hand, there is also the scientific basis for the construction of the absorbent form of coastal mining has been and will thrive here.

Fissured aquifer sediments Neogene strata (n)

Description aquifers are widely distributed throughout the study but should be completely covered by only caught by the borehole. Depth caught between 50 meters to 90 meters. Ingredients include rock reservoir sandstone, grit, siltstone with low engagement. Aquifer thickness from 50 to 350 meters. Synthesis of research results showed that only in the southeast, between Nhat Tan, Xuan La and younger is better taking water.

The experimental boreholes in this area for flow rates from 0.66 to 3,75l / sm water conductivity coefficient of soil from 55 to 840m 2 / day. Can be folded into the aquifer generally moderate. Neogen water in aquifers have very good quality due to less contamination. Urban areas such as Dinh Cong, Linh Dam, France Van are exploited for drinking water aquifers living in Neogene.

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