**4. Results and discussion**

10−9 m/s [36–38], is available to recharge the shallow groundwater. In the Margalla hills, 7–15% of the precipitation tends to recharge the aquifer system through deep fractures of variable sizes in the limestone. Recharge within the urban areas of Islamabad and Rawalpindi is limited

*T*-values are used from the results of pumping tests at 35 tube wells. Overall, *T* is set at 2.8 ×

/s for layer 3, 6.85 × 10−4 m2

for layer 7. Boundary conditions consider all the cells active with the Korang River as a constant head boundary and the Lei Nullah as a recharge boundary. Horizontal hydraulic conductivity varies depending upon the type of subsurface material in layer 1 and is computed from *T*. The initial hydraulic heads are set at 28 m from initial guess and observed heads in the field. The top of the layer 1 is set at 426.7 m above the mean sea level (masl), and the bottom of the layer 1 is set at 47 m from the ground surface including 12 m layer of aquiclude. The top of the layer 2 is set at 47 m from the ground surface. The bottom of the layer is set at 106.7 m. Therefore, the thickness of layer 2 (saturated) is considered to be 57.9 m including 12-m layer of aquiclude. The top of the layer 3 is set at 106.7 m from the ground surface. The bottom of the layer is set at 137 m. Therefore, the thickness of layer 3 (saturated) is considered to be 30.4 m including 4 m layer of aquiclude. The specific yield (required for flow-path calculations) is set at 0.06 for layer 1, 0.009 for layer 3, 0.005 for layer 5, and 0.007 for layer 7. The Korang River is considered as the constant head boundary. Lei Nullah was considered to be influent (losing) or effluent (gaining) at places that would automatically adjust the situation during the simulations of different stress period in the steady-state and non-steady state conditions. The River Package was used to assign the following values of hydraulic properties of the rivers to the model cells:

/s

/s for layer 5, and 2.78 × 10−4 m2

/s

**•** Grids 95 columns × 89 rows. The size of grid is 91.4 m (300 ft) in *x* and *y* directions

by impervious cover. The setting of the flow model is given below:

**•** Layer 1 (25 m) type = unconfined/confined (transmissivity [*T*] constant)

**•** The total modeling area is 70.7 km2

14 Groundwater - Contaminant and Resource Management

**◦** Layer 2 (12 m) type = aquiclude

**◦** Layer 4 (12 m) type = aquiclude

**◦** Layer 6 (4 m) type = aquiclude

/s for layer 1, 4.6 × 10−4 m2

**◦** Layer 3 (20 m) type = confined (*T* constant)

**◦** Layer 5 (25 m) type = confined (*T* constant)

**◦** Layer 7 (22 m) type = confined (*T* constant)

**•** Hydraulic conductance of the river bed = 1.5 × 10−4 m2

**•** Head in the river = 27 m from the top of the layer = 0.0

**•** Elevation of the river bed bottom = 27.5 m from the top of the layer = 0.0

Observed hydraulic heads were obtained for 1998 and 2003 from the previous literature review [14], while for 2007 data were collected physically in the field. When data were collected, only

**•** Number of layers = 7

10−3 m2

#### **4.1. Simulation of the groundwater flow**

First, the model was run for steady-state condition with one time step of 20 years duration. The model was calibrated by comparing observed and computed heads using the UCODE automatic calibration program [19,39]. The hydraulic conductivity and recharge values were estimated during the process of steady-state calibration. Initially, the model was run to achieve

**Figure 8.** Three-dimensional projection of observed hydraulic heads in non-steady-state condition (1998).

the steady-state condition without pumping the wells and results obtained were calibrated with the available hydraulic head of 1998, as the available heads in 2003 and 2007 were very fluctuating due to the pumping effects. Simulated steady-state hydraulic heads for different aquifer layers are shown in **Figure 11**. Vector plots indicate groundwater flows toward Korang River in the southeast. Mass balance analysis showed a good balance between the inflow and the outflow components during the steady-state condition (**Figure 12**).

For transient-flow simulations, the initial heads were taken from the steady-state model. Withdrawals were set to a realistic range of pumping rates (in the range of 0.0094–0015 m3 /s).

**Figure 9.** Three-dimensional projection of observed hydraulic heads with reference to water supply tube wells (2003).

The non-steady-state model was run for 1, 3, and 5 years. Transient-state simulations carried out up to year 2012 showed that the flow field had changed in the underlying aquifer layers because of pumping, as indicated by the arrowheads in **Figure 13**. Cone of depressions of layers 1, 3, and 7 for the southwestern area during 2008 are shown in **Figure 14a**–**c**. In the southwest

the steady-state condition without pumping the wells and results obtained were calibrated with the available hydraulic head of 1998, as the available heads in 2003 and 2007 were very fluctuating due to the pumping effects. Simulated steady-state hydraulic heads for different aquifer layers are shown in **Figure 11**. Vector plots indicate groundwater flows toward Korang River in the southeast. Mass balance analysis showed a good balance between the inflow and

For transient-flow simulations, the initial heads were taken from the steady-state model. Withdrawals were set to a realistic range of pumping rates (in the range of 0.0094–0015 m3

**Figure 9.** Three-dimensional projection of observed hydraulic heads with reference to water supply tube wells (2003).

/s).

the outflow components during the steady-state condition (**Figure 12**).

16 Groundwater - Contaminant and Resource Management

**Figure 10.** Three-dimensional projection of observed hydraulic heads with reference to water supply tube wells (2007).

(around Rawal Town), the flow is diverted toward a composite depression trough, but the flow in the southeastern area (around Pothwar Town) still moves into the Korang River. In the extreme south, the flow tends to rise where several wells are not pumping. A maximum of 20 m drawdown was observed at the end of a 3-year simulation in 2010. As a result, groundwater in the upper horizon (47 m) has already been depleted and pumping continues in the remaining permeable layer 3 through layer 7.

**Figure 11.** Steady-state hydraulic head in layers 1, 3, and 7 (after 20 years).

**Figure 12.** Mass balance during steady-state calibration.

**Figure 13.** Hydraulic head in layers 3, 5, and 7 during 2010 (non-steady state).

(around Rawal Town), the flow is diverted toward a composite depression trough, but the flow in the southeastern area (around Pothwar Town) still moves into the Korang River. In the extreme south, the flow tends to rise where several wells are not pumping. A maximum of 20 m drawdown was observed at the end of a 3-year simulation in 2010. As a result, groundwater in the upper horizon (47 m) has already been depleted and pumping continues in the remaining

permeable layer 3 through layer 7.

18 Groundwater - Contaminant and Resource Management

**Figure 11.** Steady-state hydraulic head in layers 1, 3, and 7 (after 20 years).

**Figure 12.** Mass balance during steady-state calibration.

The physical properties of the aquifer were found favorable for the development of ground‐ water with moderate values of transmissivity and specific yield. There is a continuous drop in hydraulic heads in the vicinity of pumped tube wells in Rawal Town and adjacent areas. Simulations indicated a maximum drawdown of 20 m. Existing tube wells could be safely pumped for a period of 5 years at the existing rate of discharge. However, drawdown could reach as deep as the fifth layer of the aquifer. Velocity vectors indicate that the groundwater in Rawalpindi city moves southeast toward the Korang River. Groundwater flow pattern in the layers 3, 5, and 7 is almost identical, but the velocity of flow is different for different layers.

**Figure 14a.** Cone of depression in layer 3 (1-year simulation in 2008, non-steady state).

**Figure 14b.** Cone of depression in layer 5 (1-year simulation in 2008, non-steady state).

**Figure 14c.** Cone of depression in layer 7 (1-year simulation in 2008, non-steady state).

#### **4.2. Management options for groundwater development**

Under the present water scarcity conditions, there is a need to initiate integrated water resources management programs, with site-specific interventions, especially to harness the available rainwater. This would not only contribute to groundwater recharge in the basin but also supplement the water supplies to meet future water demand for various uses. Surface water drainage system/network (**Figure 1**) carries rainwater and is a potential source of recharge to groundwater. The Soan and Korang rivers recharge the aquifer system during rainy months and are sustained by base flow at other times. Therefore, more water wells could be constructed along the Korang River where the underlying aquifer layers have good potential yield. Pumping of water wells in the western part of the study area needs to be monitored strictly in order to enable the groundwater levels to recover. Necessary bye-laws are established to restrict the overexploitation of groundwater and installation of unplanned tube wells. Similarly, bye-laws are established for restricted clearance of vegetation cover for unplanned urban development, as vegetative cover on the free catchment has proven to be an aid to groundwater recharge. The recharging system should be so designed that the amount of recharge during a year is at least equal to the amount of groundwater extracted during the year. Some of the recharging techniques may include as follows:

## *4.2.1. Dams and pounds*

**Figure 14b.** Cone of depression in layer 5 (1-year simulation in 2008, non-steady state).

20 Groundwater - Contaminant and Resource Management

**Figure 14c.** Cone of depression in layer 7 (1-year simulation in 2008, non-steady state).

Under the present water scarcity conditions, there is a need to initiate integrated water resources management programs, with site-specific interventions, especially to harness the available rainwater. This would not only contribute to groundwater recharge in the basin but also supplement the water supplies to meet future water demand for various uses. Surface water drainage system/network (**Figure 1**) carries rainwater and is a potential source of

**4.2. Management options for groundwater development**

Water-charging pounds in open spaces, dams, and check dams need to be constructed in nullahs and distributaries. Such ponds would serve as water storage for emergency as well as for recharging of the groundwater (**Figure 15**). Main parks and green belts astride main roads of the twin cities and the dissected valleys around the built-up lands are ideal places to harvest rainwater by making water ponds recharging wells, etc.

**Figure 15.** Water ponds provide potential source not only for storing the surface runoff but also for recharging the groundwater.

## *4.2.2. Infiltration using wells and boreholes*

Water can be infiltrated by injection using wells or boreholes in the areas where low-permea‐ bility strata overlies target aquifers as in the parts of watershed containing medium- to finetextured soils over calcareous material (**Figure 2**). This technique is suitable for deep-seated aquifers that form a source of groundwater for urban areas lying in the valley plains of the watershed. The water-injecting wells have advantage that recharge water can bypass thick impervious layers to be introduced to the most permeable portions of the aquifer [40].

#### *4.2.3. Water spreading*

Water is diverted from surface water runoff into infiltration basins, ditches, or low-lying areas where the aquifer to be recharged is at or near to the ground surface as in the areas with flat to gentle topography. The water-spreading method could be practiced in medium- to coarsetextured soils in the gently sloping southeastern and some central parts of the watershed (shown in **Figure 2**). The exposed rocks of limestone and sandstone in the vicinity of the urban areas also provide potential recharge environment for subsurface water (**Figure 16**).

**Figure 16.** Joints and openings in the rocks facilitate recharge to the subsurface water.
