Islamabad is often described as one of the best-planned cities of Pakistan. Yet one of the most fundamental requirements of any sustainable city – water security – has received far less attention than roads, buildings, transport systems and, continuous expansion of the urban footprint. One could argue whether Islamabad needed a Metro more than an integrated groundwater management plan. As part of this plan, Islamabad must invest in systematically recharging the groundwater that it is extracting. The Margalla Hills provide an obvious starting point. The hills are not merely a scenic backdrop to the capital. They are an important part of Islamabad’s natural hydrological system. During the monsoon, rainfall on the Margalla generates runoff through numerous nullahs and tributaries. Much of this water moves rapidly downstream, contributing to flash flooding and eventually leaving the city rather than becoming a useful part of its long-term water balance. The question therefore is simple: why should Islamabad allow valuable rainwater to rush away when the city is facing declining groundwater levels? A comprehensive solution deserves serious consideration for the development of a Margalla Foothills Water Retention and Groundwater Recharge System, incorporating strategically located lakes or small reservoirs, check dams, recharge ponds, wetlands, and recharge wells. This is not an entirely new idea. It has a substantial technical basis. A hydrological assessment undertaken by the Pakistan Council of Research in Water Resources (PCRWR) identified 13 potentially suitable locations for surface rainwater storage around Islamabad, with an estimated total rainwater-harvesting potential of approximately 64 million cubic metres. The study specifically noted that several tributaries originate in the Margalla mountain range and that surface storage through lakes, ponds, dams or weirs could be used to retain runoff. This figure is significant. Sixty-four million cubic metres is not a trivial quantity for a city struggling to secure its future water supply. Even if only a portion of this potential could ultimately be developed economically and environmentally, the opportunity deserves a proper feasibility study. Geneva, Switzerland provides a particularly relevant international precedent. After groundwater levels in the Genevois Aquifer fell by more than eight metres, the authorities did not merely restrict abstraction. They constructed an artificial recharge facility at Vessy, using treated Arve River water to replenish the aquifer, with average annual recharge of about 9 million cubic metres. Islamabad could apply the same principle at a different geological scale: retain a portion of Margalla runoff and infiltrate it into the receptive piedmont and alluvial aquifer system. Our conventional approach to urban rainwater has been largely defensive: build drains and channels to move stormwater away as quickly as possible. That approach makes sense for protecting urban infrastructure from flooding, but it is incomplete from a water-security perspective. Our approach should rather be: capture → store → infiltrate → recharge. A major reservoir is not necessarily the answer. Indeed, given Islamabad’s topography, geology, environmental sensitivity, and the experience of previous proposals, the better solution may be a network of relatively small interventions. At selected locations in the Margalla foothills, the Capital Development Authority (CDA) could construct small retention structures or check dams to slow down runoff. Downstream, water could be directed into recharge ponds and wetlands where geological conditions permit. At other locations, appropriately designed recharge wells could accelerate infiltration into suitable aquifers. A larger lake could also be considered at a technically suitable site, but its purpose should not be limited to recreation. It should be designed primarily as a strategic water-retention and recharge asset, with recreation and landscaping treated as secondary benefits. There is encouraging evidence from Islamabad that recharge works. PCRWR, in collaboration with CDA and other institutions, has developed rainwater-harvesting and groundwater-recharge sites in the capital. At the Kachnar Park site in I-8, PCRWR reported that approximately 1. 9 million gallons of water was recharged during the 2022 monsoon period, contributing to a local rise of about four metres in the water table. The intervention also helped reduce flooding by retaining water underground rather than allowing it to move rapidly into Nala Lai. More recently, PCRWR reports that Islamabad has developed a much larger network of groundwater-recharge sites. Its current programme with CDA and FGEHA includes 110 recharge sites, intended to enhance aquifer replenishment through rainwater harvesting and mitigate urban flooding. These initiatives demonstrate an important principle: rainwater harvesting is not simply about saving water at the surface; it can be used to rebuild the city’s underground water reserve. Islamabad’s water supply comes from both surface sources and groundwater. Surface water is primarily supplied through Simly and Khanpur dams, while thousands of public and private tube wells extract groundwater. But groundwater is not an infinite underground lake. It is part of a dynamic system in which extraction must be balanced by recharge. PCRWR has previously highlighted groundwater depletion in Islamabad at around one metre per year, while noting that Islamabad receives more than one metre of annual precipitation. The Council has suggested that capturing a significant proportion of rainfall through surface and groundwater interventions could help recharge the aquifers. The irony is striking. A city receiving substantial rainfall can simultaneously experience groundwater depletion because it fails to retain enough of that rainfall. We are therefore effectively mining groundwater while allowing a substantial portion of the replenishing resource to escape. That is not a sustainable water policy. The geology demands a scientific approach. There is, however, a major qualification. Not every location is suitable for a lake, check dam, or recharge well. Islamabad sits over several distinct hydrogeological systems. The fractured limestone and sandstone associated with the Margalla Hills are different from the alluvial deposits and gravel/sand aquifers of central Islamabad, while the Siwalik formations around areas such as B-17 and Sangjani present another set of characteristics. Therefore, simply digging a lake or installing recharge wells wherever land is available would repeat the very planning weaknesses that have contributed to the present problem. Every proposed site should undergo proper hydrogeological, geological, geophysical, and environmental assessment. The objective should be to identify where water can actually enter an aquifer, how quickly it can infiltrate, what quantity can safely be recharged, and whether there is any risk of contamination or undesirable groundwater movement. The institutional problem is equally important. CDA, PCRWR, the Ministry of Water Resources, universities and other agencies have already undertaken valuable work on Islamabad’s water resources. But these efforts need to be brought together under one comprehensive water-security framework. The city needs an Islamabad Integrated Water Management Plan with a clear 20–30-year horizon. The city should also establish a water balance, updated annually: how much water enters the system through rainfall and surface flows, how much is extracted, how much is recharged and how much is lost. Without such accounting, Islamabad is effectively managing its most precious natural resource without knowing its balance sheet. A lake could become more than a lake. The proposed Margalla foothills lake should therefore be viewed in a much broader context. A properly designed water body could simultaneously provide: water storage, groundwater recharge, flood mitigation, watershed management, biodiversity protection, urban cooling, and recreational space. But the proposal must be based on science rather than the desire to create another attractive feature for the capital. There is also a reason to be cautious. Earlier studies examined small dam sites around the Margalla foothills and some proposals were considered technically unsuitable. The reasons however are unknown to the author. That history should not be ignored. Instead, it reinforces the case for a new, comprehensive feasibility study using modern geological, hydrological, and remote-sensing techniques. Recent reports suggest progress on two small dam projects. Shahdara, a 10 MGD supply capacity dam in Margalla foot hills, inside ICT. The other Dotara Dam, not directly related to our topic of discussion, is a 72 MGD supply capacity carryover Dam, upstream of Khanpur Dam on Haro River in Haripur, KPK. The question should not be whether a specific old proposal for a dam was feasible. The question should be: given today’s water crisis, what combination of storage and recharge interventions can safely and economically retain the maximum possible amount of Islamabad’s rainfall? Islamabad’s greatest water-security asset may already be standing above it. The Margalla Hills receive rainfall, generate runoff, and feed the drainage network of the capital. Instead of allowing this resource to pass through the city as floodwater and disappear downstream, Islamabad should seek to retain an appropriate portion of it and return it to the underground water system. PCRWR’s Islamabad hydrogeological assessment does provide support for the coarse piedmont/alluvial material and high recharge potential near the Margalla foothills. It also identifies groundwater occurring in alluvial deposits and deeper formations. But that is not the same as demonstrating a laterally continuous aquifer directly overlying fractured Margalla limestone. This part should be resolved through scientific study. Water can move through joints, fractures, and faults in the Margalla limestone. Its matrix porosity may be modest, but secondary permeability can be high. A hydraulically connected composite system is really an interesting possibility. If this connectivity exists, a retention lake/check dam placed over the right part of the piedmont could potentially produce much more recharge than a conventional surface-storage scheme. But this model needs to be demonstrated, not assumed. A thick clayey overburden doesn’t necessarily destroy the aquifer underneath. Instead, it can make it confined or semi-confined and reduce direct natural recharge. Conversely, a relatively thin overburden over coarse gravels could provide an excellent managed aquifer recharge zone. The testable geological questions are: where does the Margalla runoff encounter permeable gravel/sand, and where are those deposits hydraulically connected to deeper groundwater-bearing formations or fractured bedrock? CDA could commission geophysics, borehole logging, pumping tests, and groundwater-level monitoring along several Margalla-to-Islamabad transects to establish whether such a connected system exists. If it does, the location of a recharge lake could be selected scientifically according to the subsurface geology rather than simply according to where a dam can physically be constructed. The objective should be to transform the Margalla foothills into a natural water bank for Islamabad. Every monsoon would then become an opportunity to deposit water into that bank rather than merely an event requiring emergency drainage. The capital cannot continue solving its water shortage by drilling more and deeper wells. That is equivalent to responding to a declining bank balance by increasing withdrawals. The sustainable solution is to reduce unnecessary withdrawals and increase deposits. CDA should therefore commission, without further delay, a comprehensive Margalla Foothills Water Retention and Groundwater Recharge Feasibility Study, beginning with the 13 sites already identified by PCRWR. The article does not necessarily reflect the opinion of Business Recorder or its owners.
Let Islamabad’s Margalla be its water bank
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