STORMWATER MANAGEMENT IN URBAN LAHORE FOR GROUNDWATER RECHARGE UNDER EXTREME RAINFALL EVENTS

Abstract

Over the last few decades, the metropolitan of Lahore has changed drastically with expansion of urbanization towards the east and south but also changed the typical character of urbanization. In particular, the drainage network has been outdated by this growth and hence the flow obstructions create ponding conditions under severe storm events. Due to increase in population, groundwater abstraction is also at increase which resulted in decline in water table of Lahore aquifer. The mechanism to be adopted would recommend dampening the extreme storm runoff and the utilization of the diverted flows in recharging the aquifer. To do so it was necessary to identify those areas that have potential for drainage carriers and also have adequate space available for recharge mechanism having and urban land use ratio between 1.2-2.75. The study focused on possibly generated extreme storm water from 10-year extreme rainfall event to recommend areas for recharge mechanism implementation across the urban land. A Dem of 2.5 m elevation has been used in order to apply a delineation processing and number of catchments have been identified along with their natural drainage network. Historical extreme rainfall events have been identified to drive a process for hydrograph generation given with peak discharges at some ponding locations. A sample catchment has been selected to calculate flood ponding capacity and number of recharge wells that can utilize the open space in order to augment ground water of Lahore aquifer. Considering minimum required spacing amongst the recharge wells, a total of 09 recharge wells could be installed per ha of open space which equates to a maximum installation of 288 wells within the 32 ha of space that would correspond to maximum recharge potential of 0.13 Mm3.