Figure 5. Contour of groundwater level for 270 days of pumping
When the pumping time is 300 days, the base flow from zone 1 to zone 2
becomes 1313.8 m3/d; at the same time, some water
flows from zone 2 to zone 1 with a volume of 41.12
m3/d, which means that the water from the wetland
recharges the piedmont plain aquifer, and the process can be described
as induced infiltration. The area of induced infiltration is initially
distributed in the center at the junction of zones 1 and 2. This is
because the pumping wells are located in the middle of the study area,
and the extent of the cone of depression formed during pumping is also
roughly distributed in the middle. The inversion of the hydraulic
gradient in the middle of the study area causes the groundwater flow
direction to change from east to west, while the edge is relatively less
affected by pumping, which can be clearly observed in Figure 5. Another
reason for setting the pumping wells in the middle of the study area is
that the south and north boundaries of the model are no-flux boundaries,
and the contour of the groundwater level is perpendicular to the south
and north boundaries. If the pumping wells are located too close to the
no-flux boundaries, with the increase in pumping time, the formed cone
of depression will definitely affect the groundwater flow direction at
the south and north boundaries, which does not match the set boundary
conditions.
As the pumping process continues, the area where the hydraulic gradient
is inverted becomes increasingly larger, while the infiltration volume
of zone 2 flowing to zone 1 increases, and the base flow of zone 1
flowing to zone 2 decreases. The base flow from zone 1 to zone 2 is
reduced to 0.69 m3/d when pumping is carried out for
1440 days. At this time, due to the reversal of the hydraulic gradient,
the infiltration from zone 2 to zone 1 increased to 2661.5
m3/d, and the water level at the location of the
pumping wells dropped to 5.0 m. When pumping was carried out for another
30 days and the simulation duration was 1470 days, the base flow from
zone 1 to zone 2 became 0, which means that the groundwater divide
formed between the wetland and the piedmont plain due to pumping had
spread to the wetland boundary, as shown in Figure 6. The groundwater in