Let Islamabad’s Margalla be its water bank

Islamabad, known as one of Pakistan's best-planned cities, has neglected a crucial aspect of sustainable urban development: water security. While roads, buildings, transport systems, and urban expansion have been prioritized, groundwater management has been overlooked. An integrated groundwater management plan is essential for the city's long-term sustainability.

The Margalla Hills, a scenic backdrop to Islamabad, play a vital role in the city's natural hydrological system. During the monsoon season, rainfall on the Margalla generates runoff through various nullahs and tributaries. However, much of this water flows rapidly downstream, contributing to flash flooding and ultimately leaving the city instead of being utilized for the city's long-term water balance.

A comprehensive solution involves a Margalla Foothills Water Retention and Groundwater Recharge System, which includes strategically located lakes or reservoirs, check dams, recharge ponds, wetlands, and recharge wells. This approach is not a novel concept and has a solid technical foundation. A hydrological assessment by the Pakistan Council of Research in Water Resources (PCRWR) identified 13 potential locations for surface rainwater storage, with an estimated total rainwater-harvesting potential of around 64 million cubic meters.

Sixty-four million cubic meters is a significant amount of water for a city struggling to secure its future water supply. Even if only a portion of this potential could be developed economically and environmentally, it would still provide a valuable opportunity for Islamabad. Geneva, Switzerland offers a relevant international precedent.

After groundwater levels in the Genève Aquifer fell by over eight meters, authorities constructed an artificial recharge facility, replenishing the aquifer with about 9 million cubic meters of treated water annually. Islamabad could apply a similar principle at a different geological scale, retaining a portion of Margalla runoff and infiltrating it into the aquifer system.

Conventional urban rainwater management in Islamabad has been largely defensive, focusing on building drains and channels to quickly move stormwater away from urban areas. However, this approach does not address the core issue of water security. Instead, the focus should be on capturing, storing, infiltrating, and recharging rainwater.

Although a large reservoir may seem like the answer, given Islamabad's topography, geology, environmental sensitivity, and previous proposals, a network of smaller interventions may be more effective. At selected locations in the Margalla foothills, small retention structures, check dams, recharge ponds, wetlands, and recharge wells could be constructed to slow down runoff and direct water into recharge ponds and wetlands.

In some areas, recharge wells can accelerate infiltration into suitable aquifers. Larger lakes could also be considered at suitable sites, but their primary purpose should be water retention and recharge, not solely recreation.

Evidence from Islamabad suggests that recharge initiatives are effective. The Pakistan Council of Research in Water Resources (PCRWR), in collaboration with the Capital Development Authority (CDA) and other institutions, has developed rainwater-harvesting and groundwater-recharge sites in the city. At the Kachnar Park site in I-8, PCRWR reported approximately 1.9 million gallons of water was recharged during the 2022 monsoon period, resulting in a local rise of around four meters in the water table.

Another recent initiative includes a network of 110 recharge sites, aimed at enhancing aquifer replenishment through rainwater harvesting and mitigating urban flooding. These initiatives demonstrate that rainwater harvesting is not just about saving surface water; it can help rebuild the city's underground water reserve.