Ditching Day Zero | Infrastructure news

Recent rains within the Nelson Mandela Bay Municipality (NMBM) as well as water loss programmes and water restrictions have pushed back day zero, with the average level of supply dams at 19%. However, NMBM’s water supply is still constrained. Lyle Francis, deputy director: Water Demand Management, NMBM, gives IMIESA an update.

“In June 2022, the NMBM came close to Day Zero. The Kromme Sub-System (Churchill and Impofu) and Kouga Sub-System (Kouga and Loerie) were critically low and NMBM were unable to extract their licenced volume of 167 Mℓ/day,” says Francis.

Fortunately, the Gariep Dam (450 km to the north of NMB) is at full capacity and can supply approximately in excess of half of NMBM’s water supply through the Nooitgedacht Water Supply Scheme (NWSS).

Nooitgedacht Water Supply Scheme (NWSS)

The NWSS transfers water from the Gariep Dam, Loerie Dam and Kouga Dam to the areas typically supplied by the Churchill and Impofu Dams (Cape St Francis, St Francis Bay, Hankey, Humansdorp, Kruisfontein, Jeffreys Bay, Oyster Bay, Patensie and Thornhill as well as the southern and central parts of Gqeberha).

Phase three of NWSS was recently completed that included the construction of a standalone 70 Mℓ/day treatment module at the Nooitgedagt WTW, a 45 Mℓ balancing reservoir at Olifantskop Farm and the installation of cathodic protection systems on both the original Nooitgedagt to Motherwell high level pipeline and the low-level pipeline There was also the building of various bulk pipelines and rehabilitation of structures, as well as the replacement of certain valves and fittings on the Motherwell to Chelsea pipeline.

“Without the Nooitgedagt supply scheme, NMBM would have run out of water some years ago, with disastrous consequences for all. Nooitgedagt will ensure that NMBM will not run out of water entirely should the western supply fail completely due to the persistent drought but will, instead, be able to provide a large portion of the metro with a continued supply of quality potable water, albeit at lesser quantities than current demand,” explains Francis.

However, there is only a finite amount of water (210 Mℓ/day) that can be transferred to the western side via the canals, tunnels and pipelines to the treatment works and the treatment works have a finite capacity of water treated per day. The net amount that can be transferred is dependent od the consumption of the north and eastern parts of the NMBM. The net result is a 30 Mℓ/day – 40 Mℓ/day shortfall.

“In addition to this, we are also experiencing operational constraints with aging infrastructure and load shedding (water cannot be pumped). For example, the transfer pumpstations that bring Nooitgedagt water to zones traditionally supplied by the western dams are running with all pumps on duty with no standbys available due the need to augment the supply to these zones,” adds Francis.

Pressure management

The metro’s water usage in 2020 was around 300 Mℓ/day, today consumption is reduced to 260 Mℓ/day, with the aim to further decrease water usage to 230 Mℓ/day. Water pressure management is considered by NMBM as the most effective real loss and water demand management intervention.

High water pressure contributes towards an increased number of burst pipes and a greater volume of water lost due to underground leaks. The aim of pressure management is to reduce pressure to an acceptable level and, therefore, actual water losses. Water pressure management decreases water consumption and increases the asset life.

A pressure management programme was accelerated during January 2021 to identify and implement new pressure managed zones across the NMB. Currently, the number of pressure managed zones is 89. These pressure managed zones are being used to force down consumption by reducing zonal pressures to achieve and estimated 1.5 bar water pressure at critical points inside discreet pressure managed zones. The average water savings to date peaked at an estimated 10 Mℓ/day(measured during November 2021) from optimisation of existing, as well as the newly constructed pressure managed zones.

“By reducing pressure with pressure management valves, we can supply water to consumers while saving infrastructure from bursts and leaks that result in water losses that commonly occur in night flow,” states Francis.

Water leaks

Francis adds that due to the aging infrastructure in the NMB, leaks are a challenge. “Maintenance and leak repair are ongoing. NMBM has a water leaks programme to fix damaged water pipes and water meters that contribute to water leaks. Four contactors were employed to repair leaks across the NMBM. Over an 18-month period, 42 800 leaks were logged, of which almost 40 000 leaks were subsequently repaired.”

Currently, the NMBM receive 1500 leak reports per week via our mobile app, call centre, website and various whatsapp groups. “Considering a single leak may have multiple reports, approximately 1000 leaks are fixed per week. We are focused on reducing repair times to reducing losses,” says Francis.

NMBM has partnered with the Nelson Mandela Bay Business Chamber to assist with the leak repair programmes at schools. The top 100 schools with the highest water usage have been identified and investigated. To date, around 46 schools have been adopted with the potential to reduce water wastage significantly.

There is also an ‘Adopt a Leak’ partnership between NMBM and the Nelson Mandela Bay Business Chamber whereby local businesses volunteer their resources and services to speed up the pace of repairing water leaks.

Areas with high concentrations of water leaks are prioritised for deploying the expertise and resources offered by business and the Chamber. A consulting engineer has been appointed to oversee the project and work together with NMBM’s Infrastructure and Engineering Directorate to manage the flow of water leak reports and resolution.

“This partnership has been extremely successful, the Chamber attended to allocated areas where reticulation leaks were identified and fixed. They even visited residents in their homes, read their meters, and retrofitted their toilets with water saving devices. They have run the ‘Adopt a Leak’ programme exceptionally well, it is something that I am extremely proud of and I hope we can continue with this partnership. The Chamber has set a goal to save one million litres of water, and they are very close to achieving it,” says Francis.

Another water saving measure has been the installation of 3636 single residential flow limiting disks. Flow limiting devices can control the volume of water that passes through the water meter on a daily basis. A round disk of the same internal diameter as the meter with a small orifice is installed at the household connection to reduce the pressure and flow to the property. The device monitors the volume used per day and will shut off the water supply to the property once the preset volume of 500 ℓ/day has been reached.

Augmenting water supply

Groundwater is a ‘sleeping giant’ and has huge potential in improving the region’s water security. NMBM conducted groundwater investigations during the 2010/11 Eastern Cape drought, and it was found that some land owned by NMBM had a high groundwater potential. Subsequently, over 200 boreholes have been drilled to locate suitable sites where high yielding borehole wellfields will produce sustainable groundwater abstraction and supply to be added into the existing surface water supply network.

The biggest groundwater project is the Coegekop wellfield that should be completed by end January 2023 and has the potential to add an additional 10 Mℓ/day to the area.

 <insert table> These sites for groundwater are being developed

LocationLow yield (Mℓ/day)Medium yield (Mℓ/day)High yield (Mℓ/day)
St. George’s Park1.42.13.6
Fort Nottingham0.81.01.8
Bushy Park7.010.213.3
Churchill (design phase)1.734.3
St Georges Park1.42.13.6
Fort Nottingham0.81.01.8
Bushy Park7.010.213.3
Churchill (Future)
There is also an ongoing feasibility study on desalination which forms part of the long terms water supply expansion.

Water consumption

While fixing leaks and using alternative water sources (like boreholes and desalination plants) to augment NMBM’s existing supply will contribute towards improving its water security, reducing water consumption is key. “We are faced with a complexity of reducing water consumption in a city with a growing population; however, our calculations show that reducing consumption to 230 Mℓ/day would alleviate significant pressure on our water supply system,” concludes Francis.

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