The City of Harare has been experiencing water problems of varying gravity over the last fifteen years. The main problems have been with the poor quality of the water supplied, the inadequate water supply as well as the erratic supply of potable water. Some suburbs like Mabvuku and Tafara have gone for years without a reticulated water supply. Most parts of Chitungwiza have gone for weeks on end without water supplies. The parts of Harare that have received water, have received water of unpotable quality.
It is therefore of utmost importance that long term as well as short term solutions to these water supply challenges be found Water is a basic human right as well as an essential driver of economic development, wellbeing and ecological sustainability. It is important that water supply and development be central to all development plans. Harare is not only the capital city of Zimbabwe, but it is the commercial hub and biggest city in the country with a population over 2 million.
It is also the first port of call for most business visitors as well as tourists. It is therefore of paramount importance that Harare lives up to the expectations of its status. The provision of adequate water of good quality should therefore be given top priority in the delivery expectations for the City.
The Causes of Water Supply Challenges
The City of Harare is located at the top of the Manyame catchment area. The city obtains its water supply from four dams; Lake Chivero, Lake Manyame, Harava Dam and Prince Edward Dam (which are also in the Manyame Catchment area and downstream of the City of Harare). Three main rivers; the Mukuvisi, Marimba and Hunyani Rivers drain into these dams. All the three rivers have their head waters around the City of Harare. This means that most of the runoff from rain falling in Harare ends up in the supply dams, mostly into Lake Chivero and Lake Manyame. The run-offs transport urban pollutants such as household waste and industrial waste into the lakes. The catchment area is also partly commercial farmland and partly peri urban farmland.
This means fertilisers and other plant nutrients which are leached from farms and plots find their way into the lakes. The plant 2 nutrients encourage growth of weeds and algae in the lakes thereby contaminating the water and negatively affecting its quality In addition, the two main Sewage Treatment Works at Firle and Crowborough are also located in the Manyame Catchment area and upstream of Lakes Chivero and Manyame.
This arrangement would be ideal if the Sewage Treatment Works worked properly, as the treated effluent would be released into the river system for recycling at the Water Treatment Works. However, like everything else the two Sewage Treatment Works have not been working properly leading to the release of partially treated effluent, and in some cases raw sewage, into the river system and into the supply lakes.
This further impact negatively on the quality of the water in the lakes. The combination of urban pollution, plant nutrients and poorly treated sewage effluent has resulted in a heavily polluted water source. The polluted water is more difficult and more expensive to treat to potable standards. The City of Harare is now using a combination of eight chemicals to treat their water instead of the normal three. They also must backwash their filters more often due to the prevalence of plants in the source water, adding to the water purification cost. The City of Harare has two Water Treatment Works; Morton Jaffray just below lake Chivero and Prince Edward near Chitungwiza. Morton Jaffray is supplied by Lake Chivero and Lake Manyame whilst Prince Edwards gets water from Harava and Prince Edward Dams. However due to the low water levels at Harava and Prince Edward Dams, the Prince Edward Treatment Works have stopped operating until the next rain season.
This has left Morton Jaffray as the sole operating Water Treatment Works. The water quality at Lake Chivero entering Morton Jaffray Water Works would normally be improved by blending it with the water from the downstream Lake Manyame which is of a better quality. The two Lakes are connected by a 13 km long sloping tunnel which terminates in a reception chamber 40m below Morton Jaffray Water works from where the water is pumped into the WTW.
However, the 4 pumps in the reception chamber have been out of service for several months leaving Lake Chivero as the only supply dam for the Morton Jaffray Water Treatment Works. Morton Jaffray has an installed capacity of producing 600million litres per day against the City’s demand of 1200million litres per day.
Prince Edward Treatment Works when operating would just add an extra 70million litres. The City of Harare’s water demand therefore greatly outstrips installed supply capacity even in the best of times. To exacerbate the supply situation further a lot the treated water is lost to leakages during transmission.
It is estimated that 30% or more of the treated water is lost through pipe leakages. This is mainly due to aging pipelines, some of which are more than 60 years old.
In summary the water supply challenges are caused by the following:
Highly polluted water source, mainly Lake Chivero Dam, due to poorly treated sewage effluent being discharged into the river system
Polluted water source due to plant nutrients leached into the river system
Polluted water source due to urban pollutants
Loss of better-quality water from Lake Manyame due to reception chamber pumps breakdown
High water losses of more than 30% of potable water through pipeline leakages
Loss of potable water at treatment works due to more frequent filter backwash
The long-term solutions of the water supply challenges include the increase of treatment capacity at Morton Jaffray to fully utilise the water from Lake Chivero and Manyame estimated at 1000 mega litres per day against the current capacity of 600ML/D. The construction of an alternative water source in the form of Kunzvi Dam would not only augment the existing dams’ capacity but would provide an unpolluted water source thereby reducing water purification costs.
However, this scheme has been in planning for years and there is uncertainty as to when it will be implemented. There are, however, short term and deliverable solutions which the City of Harare have some control over, and which can give the City immediate dividends. The source water quality of Chivero dam can be improved by effectively treating the sewage effluent at the two Sewage Treatment Works at Crowborough and Firle before discharging into the river system.The City should and can repair and maintain these basic technology STW. Stopping the discharge of partially treated effluent into the rivers by diverting such to Council farmland will also help improve the water quality. Council owned Ingwe and Imbwa farms should therefore be availed for discharge of partially treated effluent from Crowborough and Firle Sewage Treatment Works. The quality of water entering Morton Jaffray can also be greatly improved by blending water from Lake Chivero with the cleaner water from Lake Manyame. The pumps at the reception chamber at Morton Jaffray should therefore be repaired or replaced to enable the blending of the water. The discharge of industrial waste from factories in the City should be stopped by ensuring all polluting factories build onsite interception facilities according to council regulations.
In addition, all unregulated farming activities in the Manyame catchment area should be prohibited to limit the amount of plant nutrients leached into rivers. To limit water losses through leakages quick-fix leak repairs should be carried out at known leak hot spots using highly adaptable and versatile HDPE pipes and pipe specials to patch or replace the leaking components.
The Council should also adopt a continuous leak detection and repair programme. Conclusion The Harare water supply challenges are huge and need both technical and political involvement and determination. As this is a technical write-up, I can conclude by saying that the technical aspects are surmountable with adequate funding. The experts are available both in Zimbabwe and in the diaspora ready to step in. However, it is up to the politicians to step up to the plate and play a constructive role and provide leadership.
Shadreck Rangarira, Secretary for Water Development & Management, UK & Ireland Province
24th September 2019