In non-perennial frozen mountainous areas, the groundwater is mainly comprised of bedrock fissure water. The relatively developed weathering fissures and
tectonic fissures that form a dense and uniform network of connected fissures,
facilitate direct precipitation infiltration and groundwater replenishment and formation. Therefore, the fissure water on the top is generally unconfined and flows
from high-terrain areas to low-terrain areas to form runoff. Restricted by the
landforms, the groundwater is quickly discharged into the valleys as spring water
shortly after runoff formation.
The piedmont alluvial-pluvial fan receives replenishment, through infiltration,
from river flowing out of the mountain pass. Affected by topography and stratum
lithology, the river water rapidly infiltrates into the groundwater along the modern
riverbed. According to the survey, the Baligou runoff, 5–8 km from the mountain
pass in flood season and 1–3 km in normal and dry seasons, all recharges the
groundwater through infiltration. The replenishment averages 2.55 Â 10
4 m
3 /d
according to field measurements. At the rear edge of the alluvial-pluvial fan, the
runoff conditions are favorable, owning to great permeability of the thick and
porous aquifer comprised of coarse argillaceous gravel and pebble. At the front
edge, groundwater runoff slows down as there are multiple layers of aquifers
comprised of fine particles. The unconfined water on the top becomes shallow and
overflows, of which some forms the springs and rivers and some is consumed by
evaporation and plant transpiration. The groundwater at the bottom enters into the
Dachaidan Lake through runoff and finally evaporates.
According to the data from the Dachaidan meteorological station, the mean
annual precipitation registers 81.84 mm in the region and the evaporation is as high
as 2115.10 mm. In the rear edge of the alluvial-pluvial fan where the depth to water
table exceeds 10 m, precipitation provides little replenishment to the groundwater,
while in the front edge and the lake plain, the groundwater can be recharged by
precipitation due to shallow depth to water table (Fig. 5.17).
(2) Environmental background investigation
(a) Overview
• Geographical location
The landfill is located in the southern foot of Beishan Mountain north of Qaidam
Town, and it is about 7 km from the nearest village. The gully extends in NW-SE
direction with a total length of 500 m. There is no perennial surface runoff and no
sign of floods outside the gully, but a small amount of rainwater confluence in the
flood season. Of the V-shaped gully, the slopes on both sides are steep with gradient
of about 40°, while the mouth of the gully is wide and slightly flat, with dendritic
patterns on the top. The depth, width and elevation of the gully read 20–40 m, 40–
50 m, and 3500 m or so respectively. The proposed landfill has a storage capacity
of 700,000 m
3 and a service life of 27 years. According to the provisions of the
Landfill Classification by Construction Scale and Daily Processing Capacity, this
construction project is identified as Grade IV in Category IV by construction scale,
encompassing refuse dam, flood control and drainage systems, seepage control
166
5 Application Cases
tectonic fissures that form a dense and uniform network of connected fissures,
facilitate direct precipitation infiltration and groundwater replenishment and formation. Therefore, the fissure water on the top is generally unconfined and flows
from high-terrain areas to low-terrain areas to form runoff. Restricted by the
landforms, the groundwater is quickly discharged into the valleys as spring water
shortly after runoff formation.
The piedmont alluvial-pluvial fan receives replenishment, through infiltration,
from river flowing out of the mountain pass. Affected by topography and stratum
lithology, the river water rapidly infiltrates into the groundwater along the modern
riverbed. According to the survey, the Baligou runoff, 5–8 km from the mountain
pass in flood season and 1–3 km in normal and dry seasons, all recharges the
groundwater through infiltration. The replenishment averages 2.55 Â 10
4 m
3 /d
according to field measurements. At the rear edge of the alluvial-pluvial fan, the
runoff conditions are favorable, owning to great permeability of the thick and
porous aquifer comprised of coarse argillaceous gravel and pebble. At the front
edge, groundwater runoff slows down as there are multiple layers of aquifers
comprised of fine particles. The unconfined water on the top becomes shallow and
overflows, of which some forms the springs and rivers and some is consumed by
evaporation and plant transpiration. The groundwater at the bottom enters into the
Dachaidan Lake through runoff and finally evaporates.
According to the data from the Dachaidan meteorological station, the mean
annual precipitation registers 81.84 mm in the region and the evaporation is as high
as 2115.10 mm. In the rear edge of the alluvial-pluvial fan where the depth to water
table exceeds 10 m, precipitation provides little replenishment to the groundwater,
while in the front edge and the lake plain, the groundwater can be recharged by
precipitation due to shallow depth to water table (Fig. 5.17).
(2) Environmental background investigation
(a) Overview
• Geographical location
The landfill is located in the southern foot of Beishan Mountain north of Qaidam
Town, and it is about 7 km from the nearest village. The gully extends in NW-SE
direction with a total length of 500 m. There is no perennial surface runoff and no
sign of floods outside the gully, but a small amount of rainwater confluence in the
flood season. Of the V-shaped gully, the slopes on both sides are steep with gradient
of about 40°, while the mouth of the gully is wide and slightly flat, with dendritic
patterns on the top. The depth, width and elevation of the gully read 20–40 m, 40–
50 m, and 3500 m or so respectively. The proposed landfill has a storage capacity
of 700,000 m
3 and a service life of 27 years. According to the provisions of the
Landfill Classification by Construction Scale and Daily Processing Capacity, this
construction project is identified as Grade IV in Category IV by construction scale,
encompassing refuse dam, flood control and drainage systems, seepage control
166
5 Application Cases