Wa­ter af­fairs


Har­vest rain­wa­ter and re­use house­hold wa­ter – then get your own wet­land go­ing

By har­vest­ing rain­wa­ter and reusing house­hold wa­ter, you can re­duce your wa­ter bill and be­come a stew­ard of this pre­cious re­source and not just a con­sumer. Bev­er­ley Bal­lard-Tre­meer ex­plains.

South Africa’s av­er­age an­nual rain­fall, 464mm, is about half the world av­er­age. Add this statis­tic to the wa­ter needs of our fast-grow­ing pop­u­la­tion, and potable wa­ter is bound to be­come an ex­pen­sive lux­ury in the fu­ture. Wa­ter is a pre­cious re­source, not to be used waste­fully and cer­tainly not to be thrown away. Yet we do ex­actly that if we don’t make the most of rain­wa­ter and grey wa­ter.

Sea­sonal rains can be a great ben­e­fit to plants. A rain­fall of 10mm will pro­duce about 500ℓ (or 0,5kl) from 100m2 of roof­ing, and a prop­erty of 4 000m2 will pro­duce 20kl! The av­er­age home­owner could col­lect tens of thou­sands of litres of rain­wa­ter each year if they set about har­vest­ing it. Imag­ine the sav­ing on your wa­ter bill!

Har­vest­ing rain­wa­ter works well in re­gions that have heavy rain­fall or pro­longed rainy pe­ri­ods, both of which re­sult in run-off. Along with wa­ter-wise gar­den­ing tech­niques, rain­wa­ter can pro­vide much of the wa­ter needed by your plot. If you have suf­fi­cient stor­age tanks, har­vest­ing wa­ter dur­ing peak rain­fall sea­sons en­sures wa­ter will be avail­able dur­ing drought or when wa­ter re­stric­tions are in ef­fect. Mak­ing use of rain­wa­ter also re­duces re­liance on un­der­ground wells, pumps and mu­nic­i­pal wa­ter sys­tems. More­over, rain­wa­ter is free and clean.

Farm­ers and small­hold­ers have long known how to cap­ture the rain that falls on their prop­er­ties, for ex­am­ple, by con­struct­ing dams and fur­rows, and in­stalling wa­ter tanks. How to con­serve wa­ter in the home and gar­den is now be­com­ing common knowl­edge for all home­own­ers, and new tech­nolo­gies are be­ing de­vel­oped all the time. Th­ese days, a wide range of durable wa­ter tanks that can be at­tached to gut­ters are avail­able to cap­ture rain­wa­ter run-off from the roof. Some prop­erty own­ers in the plat­te­land are fa­mil­iar with us­ing house­hold grey wa­ter for land­scap­ing, and now sev­eral golf es­tates, ho­tels and com­mer­cial prop­er­ties in South Africa are do­ing the same. Age-old tech­niques of pre­vent­ing rain­wa­ter run-off on slop­ing sites are also be­ing re-ex­am­ined. >

on the amount of run-off) and plant a bor­der, veg­etable gar­den or or­chard. The same can be done to cap­ture runoff from a neigh­bour­ing prop­erty. • Wet­land, pond or bog gar­den The low­est part of a slop­ing prop­erty is ideal for th­ese types of fea­tures. Use French drains with pip­ing, or berms and swales, to di­rect run-off here.

Har­vest rain­wa­ter from your roof

Col­lect­ing rain­wa­ter from the roof is the most ef­fi­cient means of har­vest­ing. To find out how many litres of wa­ter you can har­vest from your roof per year, us­ing the na­tional av­er­age an­nual rain­fall of 464mm as a base­line, mul­ti­ply the roof area (or the area of your house) in square me­tres by 515,5ℓ. Di­vide by 1 000 to get the num­ber of kilo­litres. Deduct this amount from your an­nual wa­ter bill to see how much you will save for the year. If your an­nual rain­fall is higher, the sav­ings will be greater, and vice versa.

Rather than let­ting this free wa­ter run off your prop­erty, use it by di­rect­ing the wa­ter to where you want it or by stor­ing it in wa­ter tanks for later use in the gar­den. Which of th­ese choices best suits you de­pends on your bud­get, your land­scape and whether there is a slight slope away from the down­pipes.

• Re­di­rect roof rain­wa­ter run-off

The down­pipes from gut­ters can be con­nected to or feed into sur­face-laid flex­i­ble tub­ing or pipes, un­der­ground pip­ing (for ex­am­ple, a Flo-Pipe) or a French drain to re­di­rect wa­ter into par­tic­u­lar ar­eas. Or let the wa­ter from the gut­ter be chan­nelled along a dry stream bed lined with strong plas­tic sheet­ing topped with peb­bles. Even a shal­low chan­nel across a lawn can serve to di­rect run-off to a bor­der, >

a veg­etable gar­den, an or­chard or a pond.

A slight slope down­wards from the down­pipe is nec­es­sary. This method works par­tic­u­larly well if the ar­eas where the wa­ter is di­rected are some­what sunken, so that suf­fi­cient wa­ter col­lects there to wet the soil thor­oughly. The trendy name for such an area is a rain gar­den. If the wa­ter is used in a pond for wildlife, a sim­ple fil­ter may be needed, as bird drop­pings and pol­lu­tants may wash off the roof.

• Save roof rain­wa­ter in a tank

If redi­rect­ing wa­ter is not prac­ti­cal, invest in a wa­ter tank for rain­wa­ter stor­age. A tank is usu­ally po­si­tioned at ground level, but if you’re in the process of build­ing a house it is pos­si­ble to bury your tank un­der­ground. Tank-stored rain­wa­ter can be used in the home for bathing and show­er­ing, as well as in the gar­den – although this would in­volve pro­fes­sional plumb­ing al­ter­ations and ad­di­tional fil­ter­ing ac­ces­sories. City rain­wa­ter is not rec­om­mended for use as drink­ing wa­ter.

Rain­wa­ter tanks are avail­able in durable poly­eth­yl­ene plas­tic in a range of sizes, and in colours that blend well with a va­ri­ety of home ex­te­rior fin­ishes. Tra­di­tion­ally, wa­ter tanks have been cylin­dri­cal with a large di­am­e­ter. Nowa­days, slim­line tanks are avail­able that are ideal for small ur­ban prop­er­ties. Their 750mm di­am­e­ter means that they can be po­si­tioned in an al­ley­way or next to the garage. The slim­line tanks come in var­i­ous sizes, the largest hold­ing 2 000ℓ. Any num­ber of tanks can be joined to­gether against a wall in or­der to max­imise your wa­ter har­vest. The smaller tanks, which are only 1,8m high, could even be used in town­house com­plexes with shared in­ter­nal walls, as they would fit through in­ter­nal door­ways. Rec­tan­gu­lar tanks are also avail­able.

Pumps, level gauges, leaf traps, first-flush divert­ers that di­vert the ini­tial “dirty” roof rain­wa­ter, as well as taps, valves and other fit­tings to help con­nect your tank to your pumps and ir­ri­ga­tion sys­tems are all on of­fer.

Wa­ter tanks must be placed on a com­pletely level base so they don’t sub­side. Prop­erly laid pre­cast con­crete pavers and brick paving are able to support the smaller tanks. Al­ter­na­tively, place them on a 75mmthick con­crete base or find a metal tank stand.

• Rain­wa­ter tanks are easy to in­stall

De­cide where you want to po­si­tion the tank or tanks. Then cut a hole in the gut­ter above the tank po­si­tion and in the lid of the tank, us­ing a cir­cu­lar cut­ter avail­able from hard­ware stores. In­sert the down­pipe and seal the joins with sil­i­cone.

Run-off from a gut­ter can be di­rected into a curv­ing dry stream bed con­tain­ing ir­reg­u­lar-sized rocks to help slow the flow. If you want to di­rect the wa­ter to a pond, line the bed of the stream with strong plas­tic sheet­ing topped with peb­bles.

TOP Ter­raced ar­eas help to hold run-off on a slop­ing site. MID­DLE Con­struct paths and drive­ways with the cen­tre or one side slightly raised to di­rect run-off into ad­ja­cent bor­ders. BOT­TOM A slight swale in a lawn di­rects run-off from a paved area to a...

With suf­fi­cient stor­age tanks, har­vest­ing wa­ter from the roof dur­ing the rainy sea­son en­sures wa­ter will be avail­able dur­ing dry pe­ri­ods or when wa­ter re­stric­tions are in ef­fect.

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