Drizzle and Dams

Just a month or so ago, we heard reports that the Midlands water table had dropped by 60 metres!  Fortunately, it has been raining quite a lot since then, but don’t be fooled by the grey and drizzly days – the drought is not over.

For the first time in two summers, the Midmar-uMngeni River catchment area received good rain recently. More than 50ml was recorded at Singisi in one night, and the river was still pumping healthily, at volumes not seen for more than 18 months. The general perception is that with five dams plus the entire uMngeni River, there is plenty of water. This is not the case. This is how it actually works, explained by Penny Rees.

Midmar Waterworks purifies water from Midmar Dam, which is fed by the uMngeni River. The Waterworks sends the purified water via pipes, tunnels and reservoirs to an area stretching east to Wartburg and New Hanover; as far west as Richmond and Mid-Illovo; and south to Vulindlela and Botha’s Hill: plus Howick, Hilton, Pietermaritzburg, Sweetwaters, Camperdown, and everywhere in between –all are dependent on Midmar Waterworks, which gets its water from Midmar Dam. Midmar Dam is fed from two small catchments – the upper uMngeni and part of the Mooi River catchment.

For such a crucial river (supplying over 5 million people plus industries with water), the catchment of the uMngeni above Midmar is tiny. It’s roughly triangular, with the top corner at the N3-Nottingham Road offramp; running parallel to the highway down to the lower corner of the triangle at Midmar; then across to the north west around Midmar Dam as far as Fort Nottingham and back to the N3. That’s it.

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This small catchment can no longer supply enough water  to everyone due to growing population, industry and demand.  So Springrove Dam was built on the Mooi River. The Mooi River runs to Springrove from the Kamberg area in the Drakensberg and once trapped behind the Springrove dam wall, is piped to the uMngeni catchment.  As the Mooi River eventually joins the Tugela, which enters the ocean 70 kilometres north of Umhlanga, the action of taking water from the Mooi results in less water in the Tugela. But that’s another story!

The water of the Mooi River is gravity fed from Springrove Dam via pipeline to Balgowan where it is dumped into the Mpofana stream. The Mpofana joins the Lion’s River near Caversham Mill, and the Lion’s joins the uMngeni River less than a kilometre upstream of Midmar Dam. This transfer scheme is the only reason Midmar did not dry up last summer. So when you see the Lion’s River pumping away near Thokan’s Store, don’t think the drought has been broken or assume the catchment has had lots of rain.

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Springrove Dam is just more than half the size of Midmar. When construction was completed three years ago, it filled up in less than one summer. But the Springrove catchment has also been hard hit by the drought and for more than a year, Midmar has been artificially kept at 46% full by means of transferring water from Springrove. So, as at 21 November 2016, Midmar Dam’s back-up supply (Springrove Dam) was only 45% full and Midmar was 50% full!

Do the sums. Stop watering your gardens, washing cars, using water irresponsibly.

The recent rains are not nearly enough to fill Midmar.  The drought is now forecast to continue another two summers. We need to ensure that what little water we have lasts for as long as possible – so keep practicing your water wise habits – and hope it lasts until the drought is actually over.

 

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About Nikki Brighton

I live in a Magic Cottage near the mist-belt forest with my African dog, Dizzy. We enjoy long walks in the fields to gather wild greens, sitting on the verandah with a pot of tea, and harvesting vegetables outside the kitchen door.
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One Response to Drizzle and Dams

  1. Dean de Chazal says:

    Hi Nikki

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