Access to clean drinking water is a survival issue for a big metropolitan city like Lahore with an ever increasing population, now exceeding 10 million. With the year 2001 legislative delimitation of services under City District Government Act, the functional domain of municipal limits has expanded to the level of the District. This has important connotations for sustained water supply across both rural and urban localities given the large expanse of the District at 1,772 km2. At present, this is being managed by sole and wholesome reliance on the underlying groundwater aquifer. Against a combinatorial mix of abstractive mechanisms operated by WASA, Lahore and Walton Cantonments, DHA, private housing schemes, household bores and rural farming, the year 2015 estimated annual withdrawals from the aquifer were of the order of 2,303 million cubic meters (mcm) against a recharge of 1,999 mcm. The deficit in aquifer balance is ominous in lieu of falling water tables that have been documented and mapped across the entire District. Unless this wayward predilection for politically inspired tube well installations is checked, time is not far when the abstraction would become too expensive to sustain in terms of energy cost and adjusted cost to the consumer. And history is replete with stories of forgotten settlements that ran dry against diminished water sources.
How can a system that has been working for decades face an accelerated downfall? The answer lies in the now inordinate balance between urban growth and available space for rain-related aquifer recharge. Without the open space, the aquifer cannot replenish itself. Attempts at artificial recharge induce local recoveries and the other more perennial sources like the River Ravi has since depleted to 1/7th of its annual flow capacity following year 2000 construction of Thein Dam located upstream of Madhopur Head Works in India. Therefore, sustainability of meeting increased water demand is very much doubtful for the times to come given an average annual water table depletion rate of 0.55 m.
A report published under WWF Pakistan on “Situation Analysis of the Water Resources of Lahore” had revealed that due to excessive pumping, the water table depth in central part of the Lahore had gone below 40 meters and it was projected that by year 2025 the water table depth in most areas would drop below 70 meters. If present trends in groundwater withdrawals continue, the situation would become even worse by year 2040 when the water table depth in a significant part of the District would drop below 100 m or more.
Although increased reliance on groundwater supplies through a gridded pipe distribution network was originally articulated by consultants Camp Dresser & Mckee Ltd. (CDM) in 1975 (a year before creation of Lahore WASA) through a master plan, the decision only took into account a limited service zone of 313 km2 restricted to the urban Lahore. The decision was supported by a numerical groundwater model that predicted future depletion of water tables between 40 to 82 m.
The grid-based abstraction without the aid of overhead storages was not meant to be a permanent recommendation. In fact, city managers were not oblivious to harmful effects of an unrelenting reliance on ground waters when a 1964 feasibility report on Lahore groundwater hydrology had indicated minimum impact if 186 million gallons per day (mgd) pumpage was sustained till the year 1981. In 1969, the report review predicted 1 ft/yr decline till 1979. In Nov. 1974, the then Secretary Local Govt. had urged the visiting IBRD Appraisal Mission for Lahore Improvement Trust water and sanitation services about the alarming dependence on groundwater and reaching the limits of exploitation.
A major predictive analysis in 1988 observed historic changes in groundwater balance between 1960 and 1987; in 1960, Ravi River was receiving seepage from the aquifer over most of its length. By 1987, the river was a principal source of recharge and was feeding the aquifer over a large proportion of its reach (37 km) astride Lahore. The analysis showed maximum drawdown of about 18 m in year 2000 and 36 m in 2010.
In recent times, studies contingent with numerical modeling of actual pre-monsoonal water table data between years 2003-14 have shown that continuing pro-rata reliance on unconfined groundwaters flowing underneath Lahore would create a situation by year 2030 not amenable to recovery unless other geographically recessed sources of withdrawals are identified. These would be the areas at the very gate of subterranean flow lines coming in from across the northeastern border of Lahore District with India.
The projected groundwater level depletion should be a worrisome cause for the municipalities of Lahore; it is estimated that current (year 2018) municipal demand is about 950 mcm/yr. This equates to a flow of about 1,064 cusec and the figure is likely to increase to about 2,000 cusec over the next 25 years. It would be hard to imagine a system of water supply exclusive to aquifer abstractions pumping this huge quantity of water equivalent to the size of three large irrigation distributaries. Admittedly, to replenish this much abstraction, a very large area of land would be required which is definitely not going to be available within the leftover rural area of Lahore by year 2040.
Developing proposals for enhanced recharge would undoubtedly be on the strength of the undeveloped lands that would not be encroached with settlements in the future. The strategy may take the shape of large ponds of treated wastewaters and re-routed stormwater flows, infiltration galleries, soak-away pits and even deep injection wells. Whatever the form and factor of the recharge strategy, the necessity and preservation of agricultural lands would be a high priority and means to flexibility in planning
However, in the present milieu of an uncoordinated strategy, a reversal of fortunes would take time and attempts at aquifer recharge would at best be a partial solution to the emergent situation. It then becomes desirable to protect the agricultural and non-built up areas in a manner deemed fit through Lahore Development Authority zoning regulations. This requirement is, unfortunately, not addressed in the 2021 Master Plan of Lahore that actually projects continuing settlement expansion as far south as the border with Kasur District. (to be continued)