Tuesday, November 18, 2025

The Water Crisis: Start harvesting rainwater! 


If you are not harvesting at least some of the rain that falls on your roof, you need to start without delay. Having only a few thousand litres of water in tanks that can get you through, at minimum, a week of no water, is insurance you need. You don't want to be putting your faith in the Muni being able to supply your water all the time. 

But while a week of water is good, you need to be harvesting the rain that falls on as much of your roof as you can. Then you need to be storing the water in as many tanks you can squeeze on your property. Tanks come in all shapes and sizes so even small spaces can be used. 

An example of what's possible: 

In 2016, I put in two 5,000 litre water tanks harvesting about 140 sq m of my house roof. Then, at some stage the HOA loosened the setback requirement for tanks. They now allow a tank to be positioned outside of the building line, with certain restrictions.  I could now squeeze in another tank of  4,750 litres, which I did in 2023. If I could have squeezed in a 4th tank, I would have!  When my tanks are full, I have 14,750 litres (14.75kl) of water. I increased the roof area I harvest to 218 sq m. This is virtually my total roof area.

A quick check shows that in the last year, I used 11kl of Muni water, with 2 people living here almost permanently. Roof repairs and painting resulted in use of a small amount of the rainwater. Plus with the lack of rain I definitely wanted to preserve my 5,000L buffer supply so I switched to the Muni water for a period. Then 40 mm of rain I measured in later October filled my tanks to the brim, which currently sit at 80% capacity.

As a rough guide, 1mm of rain on 1 sq m of roof gives 1 litre of water. 


ReCap of my blog post dated 4 December, 2023:

"Sadly the ponds have many water birds, some who are permanent residents whose home is rapidly drying up. This is a warning of what could happen to the humans who have made their homes on Thesen Islands if they don’t start storing water. "

- excerpt from my letter to the HOA on 30 November 2023.   

More from my letter:

Elfrieda's response primarily reiterated the challenges and reasons behind the reluctance to pursue various water projects, as mentioned in the first board communiqué of 2023. I find this response disheartening, given the urgent need for proactive measures, especially in light of the escalating water crisis in Knysna.

The inadequate water harvesting practices across Thesen Islands have become a growing concern for me. 

I strongly believe that the HOA should play a pivotal role in addressing this issue by setting an example. Specifically, showcasing rainwater harvesting at the clubhouse would embody a 'lead by example' strategy.

Our dependency on the municipality for water becomes increasingly precarious, considering their ongoing challenges in waste collection and sewerage pump maintenance. With water restrictions already in place due to insufficient town water supply and no immediate plans to increase storage capacity, our reliance on small dams filled by river pumping poses a significant risk. Yet the cash strapped municipality, desperate for more income, is still approving a block of flats in lower town, a mall in Main Street, houses, RDP housing and who knows what other developments.

In summary, we face a critical situation with inadequate water supply, managed by an inefficient cash strapped municipality, and a growing demand for water. This is a pivotal moment that demands immediate action and collective responsibility.

Possible practical solution: Introduce an HOA requirement mandating water harvesting for every renovation project exceeding a certain threshold. This can be a first step in ensuring sustainable water practices within our community.

The Ponds

The current predicament with nearly empty ponds, following a R2 million investment, is disheartening. Sadly, the ponds have many water birds, some who are permanent residents whose home is rapidly drying up. This is a warning of what could happen to the humans who have made their homes on Thesen Islands if they don’t start storing water. 

The initial ponds were likely designed to be fed by run off but are the new ones? 

Can we investigate how we can get runoff?  

At the north end across the road there is a swale with a drain in it. When it rains, masses of water runs down the drain into the lagoon.  What about a sump pump and some piping to run the water into the top pond? There is electricity at the capped borehole. 

By my rough measuring, I estimate the clubhouse to have over 600 sq m of roof. One square meter of roof receiving 1mm of rain delivers about 1 litre of water. 10-year average rainfall on Leisure Island is about 680mm. This water could serve the needs of the HOA offices as well as contribute to the ponds. 

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