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Wetlands & Human Wellbeing, Part 1

The Environmental Importance of Wetlands

The following is an illustrated text version of a presentation entitle Wetlands & Human Wellbeing given by Dorothy Wakeling at the Highlands Presbyterian Church, Harare on the 3rd February, 2024 in honour of World Wetland Day. (At the same event Julia Pierini, C.E.O. of Birdlife Zimbabwe, spoke on Wetlands: Concerns and Suggestions, also reproduced on this site.)

This version has been divided into two parts, Part 1. Harare’s Wetlands and Their Crucial Function and Part 2. Monavale Ramsar Site: A Model for Wetland Restoration and Management.

Terms for “wetland”

Wetlands are seasonally flooded open grasslands. Alternative names for this sort of area include vlei (pronounce “flay”, from the Afrikaans), dambo (from the language of the Mang’anja people of Malawi) or mapani or matoro in Shona and ixhaphozi in Ndebele. We will use the term “wetland” below.

Wetlands in Zimbabwe as a whole

There are various types of wetland around the world, e.g. coastal, on flood plains, forest swamps, etc.  but the wetlands we are concerned with are seasonally flooded grasslands that occur in wide shallow depressions at the headwaters of drainages on the high central plateau of Africa. 

Zimbabwe’s river system (as part of this plateau) is characterized by many small headwater wetlands, with few large signature wetlands such as around Lake Kariba. These wetlands give rise to the streams and rivers of the country.

What do our wetlands look like?

When the settlers arrived in September, 1893, the above is what they found in the area now occupied by Harare. Trees only occurred on the higher ground with the natural habitat being the pristine open seasonal grassland wetlands of the Mashonaland Plateau. (We are grateful to Jonathan Waters, the author of this amazing book, who has allowed us to use this picture for wetland awareness purposes.)

There are huge seasonal differences in the appearance of wetlands.

A bulk of the water that is held in a wetland is invisible. It is either hidden by a thick layer of grasses or it is being held in the peaty soil under the grass layer.  The water table can lie two meters below the surface in the dry season and be just below the surface or visible, standing in wide shallow pools, in the wet season. 

Water revealed by digging into a wetland

Harare’s wetlands give rise to important river systems

What is special about Harare’s wetlands is the geographical location of the city.

Rainwater falls on Harare and drains into the shallow grass-covered wetlands all over the city. The grasses have thin leaves which pull the rainwater down into their heavily clumped roots and into the peaty soils where the water is stored all year round. The water filters through the wetlands which give rise to the streams and rivers which feed the city’s water-supply dam, Lake Chivero.  (In the spaces between the grasses birds and other creatures to move around and breed hidden from sight.)

In the map above the yellow area is Harare. The city lies on top of the Mashonaland Plateau watershed, in the Upper Manyame Catchment Basin, the source of the Manyame and the Mazowe Rivers which feed into the lakes downstream.  What happens in the wetlands of Harare has implications for the whole country.

A Google Earth version showing the same information as above
Lake Chivero (rimmed with invasive water plant)

Quick Tour of Harare’s Wetlands

Monavale Vlei is in the middle of this photo which looks across to Western Harare. Note the wetland loss to housing developments and agriculture. This translates into less water available for the ever-growing population. 

Here we are looking south down the Marimba River. Again showing Monavale Vlei and also the Belvedere Vlei and the Central Business District to the east (higher left).   (More construction has taken place in this ecosystem since this photo was taken.)

Above is a photograph of Borrowdale Vlei looking east from Mount Pleasant. This important wetland is a headwater of the Gwebi River, which in its turn flows into the Manyame Dam.

Here is a dry season photograph of Marlborough Vlei which lies adjacent to the Gwebi River. This is a famous wetland  which is richly biodiverse and replenishes ground water, as do all the open spaces. Notice how this wetland has been degraded by cultivation. It is also threatened with housing development.

Monavale Vlei, for example, represents an intact area of the overall headwater wetland ecosystem of Harare which is located on the watershed between several main rivers which perform many functions for the health of the environment and the human population.

Photo from Urban Nature Atlas Monavale Vlei

Harare’s wetlands are assets at our service, saving ratepayers huge amounts of money in water purification and water storage if left intact.    Ground water plays an important part in water provisioning in many parts of Harare.

Many people, young and old, have taken wetland awareness walks on Monavale Vlei. When we ask, “Where does the water in this glass come from?” we get myriad different answers! Here are Moze and Sheltania from Monavale with their glass of water!

When this crucial question is addressed to Harare’s children they come up with a variety of answers, all of which are correct in their way.

From a stream? Where did the stream begin? We have not had rain for seven months so how come this stream is still flowing?

Jimmy Muropa, Monavale Vlei Scout, is teaching Marlborough Primary School pupils about wetlands.

Wetlands provide environmental enhancement that no other ecosystem can as they:

  • Capture upland water runoff, slowing the flow and preventing erosion;
  • Provide natural water quality improvement:
    • Natural sewage systems, filtering out waste and running clean water into rivers;
    • Roots break down harmful pollutants including chemicals, separate them from the water, and use the chemicals as fertilizer for vegetation growing on the wetland (preventing inappropriately nutrient rich water from running into dams leading to eutrophication [1] and feeding, e.g., Kariba weed);
    • Reduce the cost of purification of water for human consumption;
  • Natural carbon sink, secreting carbon in the soil;
  • Allow silt to settle slowly in the wetland rather than being carried into water supply dams;
  • Reduce air temperatures, absorbing heat (as opposed to radiating heat the way roads and buildings do);
  • Provide rich source of plant and animal biodiversity, including unique habitats for some rare species;
  • Store water for prolonged periods:
    • Water seeps down to recharge ground water supplies
    • Water is slowly released into streams and rivers, many months after it has fallen as rain
  • Provide flood control – water held underground rather than released in sudden bursts;
  • Mitigate the effects of climate change – e.g. records show that rain is increasingly tending to fall in a small number of powerful storms rather than scattered showers. Wetlands can accommodate these downpours;
  • Provide beautiful vistas and opportunities for recreation and aesthetic appreciation.

The Loss of Harare’s Wetlands

All the advantages of wetlands listed above turn into problems when wetlands are lost.

This wetland habitat, which is the source of our rivers and our water, is threatened in Zimbabwe and southern Africa. Everywhere wetland areas are shrinking.

Apart from rapidly spreading building and road systems, wetlands are being affected by cultivation – thousands of people growing mainly maize in open ground near their homes. This monoculture is replacing the natural rich biodiversity, and causing artificial fertilizers to leach chemicals into the ground water.

One of the serious implications of wetland loss is flooding.

Above is Mayfield Estate just upstream from Monavale Vlei but within the same ecosystem. It floods every rainy season at great expense to house owners who are constantly having to repair their dwellings. This water runs off in drains or rivers to Lake Chivero and off down to the sea. It is lost to the precious groundwater storage of the wetlands.      

 On the other hand, here is Monavale Vlei just nearby to the houses shown in the previous photo, holding the storm waters and storing them for access to ground and lake water. It is only in the past two decades that the wetland ecosystems of Harare have been impacted negatively by cultivation and lost to housing developments. 

Above is the Avondale Stream, also known as the Rukadora or the Marimba. It is flooding after a big storm carrying with it precious topsoil from intensive cultivation. Also in this water are the fertilizers liberally scattered onto the maize fields.

Note that the topsoil has accumulated in Lake Chivero, reducing its storage space by at least 20%. And the fertilizers have to be removed from the water, along with many other pollutants, at Morton Jaffray Treatment Works, at huge expense to ratepayers.

Monavale Vlei and all other wetlands and open spaces in the city are the primary source of water for the residents of Harare.  Alternative spaces for housing development and agriculture must be agreed upon immediately if we are to keep our glasses full of water!

Implications of Wetland Loss in Harare

  • Harare is dependent upon its wetlands as they are its primary water source. Harare’s wetlands are essential for the water system and fresh water underpins sustainable development and business. In recent years Harare’s wetlands have suffered extensive loss and degradation due to population growth and increasing land pressure, coupled with weak governance and protection.
  • Wetlands regulate flow during droughts and dry seasons. The importance of the wetland biodiversity in relation to water provisioning is being overlooked by decision makers.  Loss of Harare’s wetlands will result in the City relying upon runoff during the summer months only.

Ways Forward

  • Need for mainstreaming wetlands protection in town planning processes. Conversion to development is not compatible with wise use of wetlands or sustainable development
  • Need for territorial mapping of wetlands and legislative reform to protect wetlands
  • Alternative options to cultivating on wetlands must be found
  • Alternative options to building on wetlands must be found
  • A model needs to be established for the restoration and preservation of Urban Wetlands, including community participation and educational awareness. (See Part 2 for responses of COSMO, Birdlife Zimbabwe and partners.)
  • Strides have been made towards the implementation of the Ramsar Convention but challenges remain with the full implementation. We need support for full implementation of Ramsar Convention in terms of wise use of wetlands for sustainable urban development
  • Recommend Harare as a potential candidate for Ramsar Wetland City Accreditation

[1] Eutrophication is a general term describing a process in which excessive concentration of plant nutrients such as phosphorus and nitrogen accumulate in a body of water, resulting in an increased growth of microorganisms and a dense growth of plant life that may deplete the water of oxygen. It is usually due to run-off from the land, carrying pollutants like fertilizers, untreated sewage, detergents and industrial waste.

Dorothy Wakeling

Monavale Vlei Programme Manager. Conservation Society of Monavale Trust

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