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September 18, 2016

Flooding in Lahore


September 18, 2016

Lahore’s sewerage-cum-drainage system was built nearly 80 years ago for a small city with a population of a few hundred thousand. Today’s rulers want it to work for a mega city of 10 million without any major addition made to the wastewater infrastructure.

Whenever there is heavy downpour, Lahore gets flooded – bringing life to standstill. During the rains people remain stranded in traffic jams for hours owing to water on the roads.

The issue is that Lahore city does not have a separate system for carrying surface water and sewage. The same underground pipes and open drains carry both sewage and storm water which choke up when their intake exceeds much beyond their capacity post rains. In 2009, Wasa statistics showed the city produced 3,125 cusecs of sewage daily. By now, this quantity must have increased by a few hundred cusecs.

A decade ago, Nespak had conducted studies on the city’s sewerage and drainage systems and presented solutions for improvement, but the authorities did not implement these proposals. According to the Nespak research, the city needs separate channels for the proper disposal of sewage and rainwater. Here the technical jargon needs to be clarified. The term ‘sewerage system’ is used for channels carrying sewage and waste water while ‘drainage system’ means channels that carry only rainwater or surface water.

The present drainage system can work without any major problem when rainfall is up to 25mm but beyond this mark it chokes up. This year, Lahore received intense rain spells up to 120 mm. The network of sewer lines and major drains do not have the capacity to take away excessive rainwater to River Ravi. As a result, it drains out from streets in 8 to 12 hours post rains or after one or two days if downpour touches the 200 mm mark as was the case in the 2004 monsoons.

Since ages, the city’s eight open natural nullahs (storm water drains) such as Hudiara, Satto Katla etc take all the water from the city to River Ravi. These eight drains wind through length and breadth of the city. In the late 1930s, when the city’s sewerage system was built for the first time, it was also connected to these main nullahs. This system worked till the city was small but collapsed with a massive growth in population – from 350,000 in 1947 to 10 millions in 2016.

During the last 70 years, the sewer length has increased from a few hundred km to nearly 5,000 km, but no major drain (a channel that connects small sewer lines to the river) has been added to the system. Moreover, large swathes of dirt surface and green belts in and around the city used to absorb showers and now have been converted into metallic roads and concrete buildings. This water is also now carried through the sewerage system.

To makes matters worse, the existing sewer lines are quite small in capacity and in a dilapidated condition; most of them were laid 50 to 60 years ago. For example, a 50-year old sewer line of 9-inch diameter caters to the needs of Gulberg, which has turned from a residential area into a busy commercial district with high-rise buildings.

The same is the case with many other localities. According to Wasa officials, more than half of the city’s sewage pipes have completed their normal age of 25 years and thus keep breaking and cracking owing to gases in the waste water passing through them.

In certain parts of the city main sewerage lines simply do not exist. For example, until four years ago, at Multan Road, a main artery of the city with new residential areas on its both sides, there was no main sewerage line to take sewage from the localities to a main drain or the river. Waste water used to accumulate in empty pieces of land around the localities.

In southern Lahore, where massive expansion of residential localities has taken place, a sewerage system with a length of nearly 290 km is required, but proposals regarding this are gathering dust.

An old, worn-out sewerage-cum-drainage keeps working somewhat thanks to 12 disposal stations installed where the main drains fall into River Ravi. These pumping stations suck, lift and throw away water from the drains into the river so as to speed up flow in these channels.

Additionally, 80 small disposal stations help accelerate the flow of water from small sewer lines into the main drains. This is the only major investment our governments have made in the city’s water-disposal system. But this is not enough to save it from flooding during and after intense rains.

In 2009, in light of the Nespak finding, Wasa Lahore proposed a mid-term plan with the building of six additional major drains and sewerage lines. This project’s estimated cost was around Rs15 billion at that time. The authorities dismissed the project, except one small portion of it – a main sewer line at Raiwind Road. This line was completed last year.

In the long run, as suggested by Wasa in 2009, an investment of Rs39 billion was required for laying all the required sewerage and drainage lines. Obviously, now this would cost more than double the original estimate. This proposal includes two main drainage systems – 77-km for the central zone and 220-km for the southern parts of the city.

In the short run, the city’s submergence in rainwater can be mitigated to some extent with the building of a 10-km trunk sewer along the Cantonment drain and a 9-km main line along Ferozepur Road. It is estimated that both these lines will cost nearly Rs12 billion over a period of two years – not a huge amount considering the billions being spent on other infrastructure projects.

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