How to supply an ever-growing city with water?

IMC is rehabilitating the water supply system of Sierra Leone’s capital city Freetown to the benefit of 600,000 people. From space constraints to competing needs, challenges are rife.

Wednesday 08 November 2017, Private: Philippa Jefferis, Private: Lorenza Geronimo

It is estimated that 54% of the world’s population now lives in urban areas. That proportion is expected to increase to 66% by 2050.

Global population’s growth could add another 2.5 billion people to the number of urban dwellers within the next 32 years, with 90% of that increase concentrated in Asia and Africa.

This makes Sustainable Development Goal 11 – Sustainable Cities and Communities – even more critical. SDG 11 states the aim to make cities and human settlements inclusive, safe, resilient and sustainable. While this definition is easy to understand, the concrete measures that need to be taken to achieve this goal are far from clear.

For IMC Worldwide, working on behalf of the UK Department for International Development (DFID) and the Guma Valley Water Company, this is a very real challenge in Freetown, Sierra Leone. IMC is leading a consortium that includes Atkins and BAM Nuttall to develop a solution to the city’s poor access to water.

Guma Dam, which was built in early 1960s, is the major source of the water supplied to Freetown.
Guma Dam, which was built in early 1960s, is the major source of the water supplied to Freetown.

Freetown’s water supply is in a critical situation. It relies almost exclusively on a single source, the Guma Dam, which was built in the early 1960s. Between the time of construction and today, the number of dwellers has increased from around 100,000 to 1.06 million people.

Over half the water that enters the system is lost due to leakage from the deteriorated network and informal ‘spaghetti’ plastic pipes. These have grown exponentially over the past 20 years to keep up with the city’s booming population.

Because of the network leakage and the high pressures at which water is supplied to the west coast, by the time water reaches Freetown’s central areas flow and quantity are lower, and then almost non-existent in the densely populated east of the city. This forces much of the population to seek informal sources, which increases health hazards and the risk of disease.

Spaghetti of hose pipes are unofficial ways of increasing water distribution.
Spaghetti of hose pipes are unofficial ways of increasing water distribution.

To improve access to water for the 600,000 people who live in the eastern part of Freetown, we will rehabilitate and extend the city’s water network by around 80 kilometres.

Balancing competing priorities

As with all cities, there is a battle of space and who gets priority is never an easy call to make. Engineering design of infrastructure needs to consider what is in place and ensure it can continue to perform its designated function.

Within this project, we are trying to fit new pipes within a city that has sprawled in all directions. The Roads Authority insists that all utilities, including watermains, are laid between the drains and buildings walls. However, this space is often too narrow.

Trying to find best solution that will cause minimal disruption.
Trying to find the best solution that will cause minimal disruption.

We will need to find a compromise as to where the pipe goes and what impact that will have on either the road or the water supply network. The decision will have to consider the requirement for future maintenance of both infrastructure.

What further complicates the situation is that some of the original pipes throughout Freetown were laid out in the open. However, as the city has grown, they are now surrounded by houses. To access and upgrade them while ensuring that residents in the area are not affected is challenging.

Here is where achieving SDG 11 becomes complex: the need to provide access to infrastructure for the many without negatively impacting a few.

The Freetown Water Rehabilitation project is at the early stages of design, but there is a need to act quickly. Decisions will have to be made, and balances found to ensure that the design of the water supply is inclusive, safe, resilient and sustainable.

Cover photo: Development Planning Unit University College London, photo made available on courtesy of Creative Commons License

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