DROUGHT
Gauteng’ s main dams explained
Alittle simple hydrological geography will make it plain to you which Gauteng ' s dams,( notably the Vaal Dam) aren ' t filling as fast as we ' d like because, while Gauteng is awash( literally, if you were in Gillooly ' s Interchange a few weeks back) with rain. The simple reason is because not much rain has fallen yet on their catchment areas. The Vaal Dam ' s catchment, for example, is largely the highlands around Standerton and Ermelo. Rain that falls over Gauteng flows west and north. Thus, insofar as Gauteng uses water from Roodeplaat, Bon Accord and Hartbeespoort Dams our rainfall is helpful to the dams, but that which falls on the south of the Witwatersrand ridge flows into the Vaal River, replenishing the Bloemhof Dam, thence into the Orange, and thus to the South Atlantic on the West Coast. Notably, rainfall in this area does not reach South Africa ' s largest dam, the Gariep, on the Orange River, as the
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the area that you use grey water on frequently, giving parts of your garden a break from receiving a constant dose of what is in effect a weak liquid chemical fertilizer. While“ proprietary” grey water filter systems are now available, a handy smallholder could easily build a low-cost system comprising a gravel-and-sand filter and storage using 210 litre drums both for the filter and, in tandem for storage of the filtered effluent, the number of storage drums dependent on the size of the household. A more profitable use of grey confluence of the Vaal and Orange takes place further down the Orange at Douglas, northwest of the Gariep Dam. Rain which falls to the north of the Witwatersrand ridge flows into various northflowing rivers, notably the Crocodile River, and into Hartbeespoort Dam, and then into the Limpopo River on the Botswana border. The Limpopo, in turn, forms South Africa ' s northern border and, onward, the eastern boundary of Mozambique ' s Parque Nacional, before it empties into the Indian Ocean just west of Xai-Xai. Incidentally, many visitors to Gauteng wonder why, even in times of drought when other rivers might run dry, the Vaal River near Vereeniging and Van der Bijl Park is always full of water to the same level. That ' s because the river as it flows past those two towns is effectively a 64km long dam itself, its waters held there by the Barrage, a 10m high spillway across the river between Van der Bijl Park and Parys completed in 1923.
WATER
water, perhaps, is to replace that( fresh, clean, drinking quality) water which flushes one ' s toilets, with grey water. Filtered and deodorised, grey water repurposed in this way will actually make a saving to overall water usage, rather than merely watering a small patch of plants and lawn. US plumbers ' studies show that an individual using an old-fashioned cistern toilet will use about 71 litres per day, while one using more modern water-saving devices( including modern dual-flush systems) will use about 35 litres a day.
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