HomeOpinion & AnalysisGeology sheds light on role of wetlands

Geology sheds light on role of wetlands

The disaster befalling wetlands across our capital city and nationwide is a very real but conveniently ignored crisis that should concern us all.

Opinion by Rosie Mitchell

Few people recognise the urgency with which these areas need conserving and restoring to original condition.

It’s not just about species habitat, biodiversity and greenbelt conservation. Species, many of them at the beginning of the food chain, and our last remaining city greenbelts, are indeed being lost, and this matters very much, too.

However, fundamentally, this emergency is about access to water for those both in Harare and downstream, dependent on the rivers supplied by these wetlands (also called vleis).

It is estimated by experts in the field that 6,5 million people stand to run out of water because of this resolute denial of the reality that without these vleis to capture our annual rain water, store it, filter and clean it at zero cost, then release it into rivers and thence into dams, there will be no water supply at all.

Already less than 60% of Harare’s water requirement can be supplied by the authorities, the rest, in the absence of any alternative, being privately sourced by digging a constantly rising number of boreholes, many of these, now running dry.

Fundamentally, we do not have enough water because our wetlands are drying up, no longer providing their amazing, and free, water purification, storage, supply, and flood prevention services, to our population.

Collective protest necessary
Destruction of wetlands is happening because we, the millions-strong population, fully dependent on these services, stand by and watch their destruction by illegal, environmentally devastating activities; cultivation, dumping, and worst of all, building, without raising a collective protest.

Without collective action to stop the destruction, the few lone warning voices can but repeat the mantra, over and over, till the penny drops on a city wide, then nationwide level — no wetlands, no water.

Harare built over massive, hard rock
Harare is built in an area where the bedrock beneath us is either igneous or metamorphic in origin and as such, is very hard, and does not absorb any water, except where a few underground spaces have developed over the ages through weathering, fracturing and jointing of this hard rock.

It is from these limited underground spaces, where water can collect, that the city’s boreholes draw their water. A very large portion of the city in the southern and eastern parts is built over massive, hard, granite, including Amby, Msasa, Cleveland, Chikurubi, Greendale, Athlone, Hatfield, Highfield, Waterfalls, Mavbvuku and part of Borrowdale.

Most of the country’s vleis, the capital’s included, are situated over granite, where they have developed naturally over the aeons.

The Cleveland, Mabvuku, Greengrove, Prospect, Budiriro and Manyame Wetlands in Harare are all vleis situated over granite and as such play an essential hydrological role by absorbing, holding and filtering rainfall which later trickles steadily from these sponge-like areas into the Mukuvisi, Ruwa, Manyame and the many other rivers in the catchment area, feeding Lake Chivero, Harare’s primary water source.

This being so, it seems somewhat obvious that the effective protection of these vleis, and others feeding other rivers, which in turn feed other dams, is urgent, given the water shortages affecting us all.

Few people can afford a borehole, and there are now too many of these in any case. With limited water available, many dry up seasonally and some, of late, permanently. Just because you cannot see the millions of litres of water held by a vlei as you roar by in a car or kombi, does not mean it is not there.

Take a walk in the vlei in the dry season, and the water stored there underground in the rich, spongy vlei soil will not be obvious. Return in the wet season, and you will need wellington boots to traverse most parts of the vlei, which will be thoroughly waterlogged, very muddy and squelchy!

I first began running, and have done, and do, much of my running still, in nearby vlei areas and have observed this first hand over several years.

The changing seasons and the resultant dramatic changes that take place in vleis, is one of the reasons I like running in these areas so much, as it is fascinating to observe and experience these hydrological alterations. My routes alter radically accordingly to the seasons.

Much of the area becomes impassable in the wet, unless I throw caution to the winds and decide just to wade, get covered in mud, and be damned! To enjoy a vlei in its original, pristine condition, visit the fully protected Monavale Vlei, at the end of Fenella Drive — and experience the differences.

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