RESULTS & DISCUSSION
The calibrated model was run for 20 years period i.e. 10 years historic
simulation (2011-2020) and 10 years prediction period (2021-2030) based
on current/ actual abstraction scenario and different anticipated
scenarios. The past 10 years (2011-2020) rainfall data was used for
historic simulation and the same trend was used for the prediction
period with one-year stress period.
Scenario 1 (Current/Actual
Pumping)
In scenario 01, actual abstraction was put in historic simulation and
the same rate was used for the prediction period without any change.Figure. 6 shows the simulated results for 10 years historic
period for the year 2020 with a maximum drawdown of 11 to 15 m in the
industrial area and 5 to 7 m in the agriculture area. Figure. 7depicts the simulated results after 20 years for the year 2030 observing
anticipated drawdown up to 20 m in the industrial area and up to 10 m in
the agriculture area. A negative drawdown of 2 to 4 m has also been
observed in some areas where there is less or no groundwater
abstraction. The average drawdown was calculated for the historic period
and the prediction period. An average drawdown of 05 m @
0.5 m/year occurred in the 10 years historic period (2011-2020) and the
same is anticipated in the prediction period (2021-2030) with the
current abstraction rate.
Scenario 2 (Projected
Abstraction)
In scenario 02, the actual groundwater abstraction was assigned to the
model in the historic period however, a projected abstraction was used
in the prediction period based on the cement industry expansion &
population growth rate. The regression analysis between population
growth rate and abstraction rate (domestic + agriculture) was made based
on historic data. Based on the analysis, the current abstraction
(domestic + agriculture) was projected @1.3% per annum in the
prediction period and the current industrial abstraction was projected
@10% per annum keeping in view the water demand for future expansion of
the cement industry. The increase in industrial abstraction in the
prediction period is a hypothesis, based on the expected installation of
cement factories in the study area.
Figure. 8 represents the simulated results after 20 years for
the year 2030 showing maximum drawdown up to 24 m in the industrial area
and up to 12 m in the agriculture area. The simulated results depict
that the projected abstraction in the prediction period resulted in an
even worse scenario. The average drawdown was calculated for the
historic period and the prediction period. Anaverage drawdown of 05 m @ 0.5m/year occurred in the 10 years
historic period (2011-2020) and an average drawdown of 7.4 m @ 0.74
m/year is anticipated in the prediction period (2021-2030)
Scenario 03 & 04 (Controlled
Pumping)
After a number of trial-runs, with various percentages of controlled
(reduced) pumping, it has been observed that a 20 to 40% reduction in
current abstraction leads the groundwater system to the equilibrium
state. From these trial-runs, two scenarios of controlled pumping i.e.
20% and 40% reduction in current abstraction are illustrated here. The
current/actual groundwater abstraction was taken in the historic period
but reduced by 20% & 40% in the prediction period in scenario 03 and
04 respectively. Figure. 9 represents the simulated results of
scenario 03, after 20 years for the year 2030 showing maximum drawdown
up to 17 m in the industrial area and up to 7 m in the agriculture area.
The average drawdown was calculated for the historic period and the
prediction period. An average drawdown of 05 m @ 0.5 m /
year occurred in the 10 years historic period (2011-2020) and an average
drawdown of 2.1 m @ 0.21 m/year is anticipated in the prediction period
(2021-2030).
Similarly, Figure. 10 represents the simulated results of
scenario 04, after 20 years for the year 2030 showing maximum drawdown
up to 15 m in the industrial area and up to 05 m in the agriculture
area. The simulated results of scenario 04 for the year 2030 are almost
identical to simulated results of scenario 01 for the year 2020 showing
no change in the prediction period. The average drawdown was calculated
for the historic period and the prediction period. An
average drawdown is 05 m @ 0.5 m /year occurred in the 10 years historic
period (2011-2020) and an average of zero drawdown is anticipated in the
prediction period (2021-2030)
Scenario 5, (Managed Aquifer
Recharge)
Due to high altitude and rolling terrain the canal irrigation system is
not present in the study area. Therefore, groundwater is the main source
of agriculture. The impact of River Jhelum was assessed by assigning
GHBC to the model, but no effect was observed on the simulated results
due to the significant difference in elevation of the river and the
study area. The recharge in this area is mainly from precipitation. The
recharge to groundwater generally varies from 15 to 20% of the total
precipitation depending upon the soil, land use/land cover, and
intensity of the precipitation (Augustyn,
2020). The annual precipitation in the study area is averaged at 626 mm
in the last 10 years (2009 to 2019). Therefore, rainwater harvesting
through open surface ponding is the most feasible method of MAR. The
recharge ponds are the common approach for MAR that involves surface
infiltration through ponds to induce rainwater into the aquifer
(Grau-MartÃnez et al., 2018).
The watershed of the study area was delineated using ArcGIS as shown inFigure. 11. The catchment area of the watershed is about 70
km2 which contributes 32,789 m3/ day
inflow caused by annual precipitation. MAR technique was applied by
assigning 03 ponds/lakes of size 1950 m x 650 m x 3 m each to the models
on appropriate places to accommodate flood runoff in the prediction
period. Figure.12 represents the simulated results of scenario
05, after 20 years for the year 2030 showing maximum drawdown up to 13 m
in the industrial area and up to 7 m in the agriculture area. The
average drawdown was calculated for the historic period and the
prediction period. An average drawdown of 05 m @ 0.5 m /
year occurred in the 10 years historic period (2011-2020) and an average
drawdown of 1.6 m @ 0.16 m/year is anticipated in the prediction period
(2021-2030) in scenario 5.
The mass budget of the groundwater system of the study area represents a
natural aquifer recharge of 53,016 m3/day against the
total abstraction of 75,283 m3/day under scenario 01
and the pond/lakes contribute 13,333 m3/day
infiltration to the aquifer under scenario 05 as shown in Figure
13 .
Figure. 14 represents the comparison of the scenarios analysis.
Up to the year 2020, all scenarios give the same trend representing
groundwater depletion in the past which is defiantly a non-favourable
condition. Any increase in current abstraction in case of agriculture /
industrial growth would cause extra pressure on groundwater resources as
evident from the results of scenario 02. Scenario 04 is the most
favourable scenario that can bring back the groundwater system to
equilibrium as there is negligible drawdown in the prediction period
with a 40% reduction in current abstraction. Even the 20% reduction in
current abstraction can reduce the drawdown significantly. The MAR
through open surface ponding would be more helpful in aquifer recharge
as it contributes to the aquifer recharge significantly.
Figure.15 shows the flow path of simulated groundwater from the
low abstraction zone (agriculture area) to the intense abstraction zone
(industrial area). The sacred pond is located near the boundary of the
industrial area and inward flow direction toward the industrial area
influences the natural flow path of groundwater recharging the pond.