Author: Nasir Ali
Ali, Nasir, 2018 Groundwater Assessment of the Peshawar District and its Potential for Future Demand, Flinders University, College of Science and Engineering
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A three-dimensional numerical model of the Peshawar District groundwater flow system has been developed with the aim to assess groundwater flow patterns in response to abstraction. The reliance of the population, agriculture, industrial and commercial activities on groundwater has put this resource under stress. Despite being such an important source of fresh, potable water for the entire district, the Peshawar groundwater system is poorly understood and under studied. Unregulated abstraction has led to a decline in the water table in densely populated areas, especially Hayatabad. This is an indication that the current rates of groundwater abstraction are unsustainable.
The hydrological and geological data of the Peshawar District was integrated to make the conceptual hydrogeological model of the area, which became the basis for the numerical modelling. Using the computer code MODFLOW-2005 (Harbough, 2005) and the model user interface ModelMuse (Winston, 2006) the numerical modelling of the area was carried out by considering the steady state condition with the geological unit of two layers. The top layer is the shallow unconfined aquifer while the deep bottom layer is the semi-confined aquifer.
The model extends around 45km in E-W and 50km in the N-S direction with a total model area of 1745 km2. The grid cell area is 2500 m2 with grid size of 50m both in x and y direction. The topographical map and the raster image of the project area was imported to the MODFLOW-2005 model using ArcGIS (Arc Map 10.4.1). Based on available pumping tests and previous studies on the lithology of the Peshawar District, the hydraulic conductivities of the shallow and deep aquifer were assigned. These initial values were altered during the model calibration process. Groundwater recharge in the area constituted recharge from rainfall and infiltration from irrigation.
The model was run under steady state conditions with rainfall and irrigation losses as recharge inputs. The flowing river is in hydraulic connection with the model area and a considerable amount of water flows into the model domain, while the abstraction by pumping accounted for a loss in groundwater from the system. The drainage channels in the model also contributed to discharge by draining the water towards the river, while the water flowing as base flow towards the river also contributes as a discharge from the system. Based on the model results the average linear velocities, hydraulic gradients and flow directions in both layer 1 and 2 were determined. Based on the analysis of the water budget, hydraulic heads and through the assessment of flow patterns an improved understanding of the hydrogeology of the project area was obtained. The calibration of the model also allowed model sensitivities to specific input data to be determined. The model findings about the flow direction indicates that the groundwater flows from the south to north -east and from west to the east towards the Kabul River. The water budget analysis indicates that the reliance is more on the Kabul River, which contributes almost half of the water to compensate the pumping from the model area. Thus, for a sustainable groundwater development, the Kabul River flow and its usage in the upper catchment areas from where it originates would play an important role regarding the future groundwater development of the model area.
This modelling exercise has been made to represent the real-world situation of the project area, therefore uncertainties are associated due to the simplifications. The boundary conditions, scarce data, and the lack of the detailed hydrogeological understanding may have an associated uncertainty. Therefore, it is important to consider the limitations when extrapolating or interpreting these groundwater modelling results.
Keywords: Groundwater Modelling, MODFLOW-2005, ModelMuse, Assessment, Aquifer, Groundwater Abstraction
Subject: Water Resources Management thesis
Thesis type: Masters
Completed: 2018
School: College of Science and Engineering
Supervisor: Ilka Wallis