DOMESTIC HARVESTING OF RAINWATER IN GREATER CAPE TOWN

The worst drought in Cape Town continues unabated in “The Fairest Cape in all the circumference of the Earth” (Francis Drake, I believe), and lately we have lived our daily lives, from morning till evening, to the surrounding background syncopation and “heavy-metal” throb and pulse of borehole drilling machines. Like giant mosquitoes, they probe the fragile, dry, skin of our gardens in order to suck the life-blood of the water-bearing layers below.

I fear that these thirsty bores that surround my home of 50 years bode ill for the future productivity of my hitherto trusty well point, and I have distinct reservations about tapping the aquifers below while my roof-water continues to find its way down to the sea. The proposed tapping of the major aquifer under the Cape Flats will also threaten the Phillip Market Gardens, with knock-ons of job loss, pollution and diminished, vital, food production.

My depleted, stagnant swimming pool has a new lease on life, this time not as a recreational focus, but as a storage vessel. Cleaned up and spruced, it now awaits the first flow of the rainwater that will once again fill it, from my roof, via new gutters and piping. This installation cost about 50 per cent that of the average borehole and will not be subject to future controls, such as metering of borehole water, logbooks and restrictions on watering times. This freedom will last into perpetuity! This process is largely driven by gravity, energy- negative, other than for minor irrigation pumping. Further mental wanderings produce the following, startling, theoretical realities! I have attempted to peg the finite realities, such as the actual number of households in the greater Cape Town, but will estimate half a million! I note, from the City Dam Storage Level Dashboard that the Total Capacity of our major dams is around 898 221 million litres.

These dams have fixed catchment areas and it would be pointless and wastefully expensive to increase the capacity of these dams unless assured of a sustained increase in our future rainfall. What is required is a new expanse of catchment, which could be provided by the hitherto unharvested roofs of the city!

It’s been postulated that if each household provided harvesting and storage of 2 000 litres, the potential total would be (500 000 × 2 000) a million litres! This figure does not purport to be 100 per cent accurate but gives some idea of the possibly staggering potential! More than double the existing storage.

It is noted that the present purchase price of PVC storage vessels equates to about R2 500/kl which then equates to R5 000 per household. The cost of this increase would, inevitably, be borne by the home- owner, but this would be an investment, rather than possible future increases in municipal rates or levies to finance alternate water sources such as desalination, which has the additional knock- on effect of energy-drain.

It would certainly also be very beneficial to the city, province and state to consider financing incentives or rebates to encourage moves in this positive direction, which could facilitate immediate execution, rather than years of planning and construction.