Home » Governance » Siltation Threatens Chivero Water Supplies

WATER woes for Harare and its satellite towns are set to worsen as siltation at the main water source, Lake Chivero, reaches unprecedented levels. Harare City Council officials, water experts and environmentalists admitted this week that the silting up of the capital’s main source of water was now a major cause for concern as it has begun affecting the pumps that draw out water from the reservoir to Morton Jaffray Water Works.

The deposition of silt into Lake Chivero has reduced its total storage capacity by an estimated 20 percent. The pumps are being clogged up by severe sedimentation resulting in them constantly malfunctioning. “We have been facing challenges with pumping water from the reservoir. Silt has now overwhelmed the intake pumps,” said Clifford Muzofa of Harare City Environmental Department.

Morton Jaffray Water Works has been undergoing rehabilitation as part of a Harare Water Plan to cost US$2,95 billion. To date Harare, Chitungwiza, Epworth and Norton towns are served from two pumping sites, Morton Jaffray water works and Prince Edward water works in Seke. The two have been able to pump a meagre 450 mega litres per day of potable water.

It is envisaged that under the US$144 million loan facility from the Export-Import Bank of China to go towards the rehabilitation of the water works, the city will be able to reach its original pumping capacity of 614 mega litres per day. Environmentalists have long warned that rampant urban agriculture in the lake’s entire catchment area would eventually completely silt the lake.

Christopher Magadza, a biologist and a leading expert in inland water, said the lake now has a projected six month water storage capacity owing to the high rate of siltation. “On our last count the lake had lost about nine metres due to silting. We should be thinking of building an alternative water source considering the rate at which the lake is silting,” said Magadza. The Nobel laureate said the issues of abuse of Harare wetlands, stream bank cultivation and climate change have had a lot of impact on the water reservoir.

Tamuka Nhiwatiwa of the Biological Sciences at the University of Zimbabwe, who is part of a team running a project on two of Harare’s rivers, Gwebi and Marimba, concurred with preliminary studies they conducted that indicate that siltation is on the increase. According to Nhiwatiwa, urban agriculture has been a major contributor, submitting that scientific consensus is that developments on wetland will ultimately jeopardize the supply of clean drinking water to the city, as wetlands are primarily natural filtration systems.

In addition, local ecosystems will disappear and flooding could occur as natural waterways become obscure. Lake Chivero has also been under threat from pollution from sewerage effluent, industrial and domestic waste, fertilizer and pesticide from peri-urban agricultural activities in the catchment area. Lake Chivero (formerly Mcllwaine) was built in 1952 and lies 29km southwest downstream of Harare, the capital of Zimbabwe on the Manyame River.

It has a capacity of 250 106 cubic metres, is 225 metres deep and a surface area of 2 630 hectares. The lake is Harare’s main water supply reservoir which is one of seven Ramsar sites of Zimbabwe designated under the Ramsar Convention on Wetlands, which provides a framework for wetland conservation and asks that nations promote the sustainable utilisation and conservation of wetlands.

Source : Financial Gazette

Archives