Household-level water storage systems – why install tanks?

Install the biggest water tank system that you can afford or accommodate.   

Why?

• Clearly “water scarcity may from now on be the new normal” in SW Cape. The dams will surely fill and empty again but the trend (due to climate change?) now seems to be towards diminishing average annual rainfall. So water shortages will happen again and again; the only question is when? Therefore, households should change water consumption habits, actively practice water re-use and creatively conserve and store water.
• A peculiarity about the topography of the SW Cape argues for a different approach. Most of the population lives in low-lying areas near the sea but are reliant on fresh water from dams located in the distant mountains. Interestingly, however, more than enough rain falls each year in the low-lying areas to satisfy most needs; but it is not practical to collect and store this rainfall run-off in large dams. So every year, most of this water runs unused into the sea.

So consider this: if one takes these two aspects together – reduced consumption and topgraphically available water – it becomes apparent that a potent solution lies within the hands of most households. And what’s that? Obviously, install appropriate rainfall water capture/storage systems in every home.

The simple but critically important outcome would be that fresh water is then captured precisely where it is needed. With care, no filtration is needed and in many cases by locating the tanks properly, little or no pumping is required. Careful calculations are needed but desk-testing many variations shows that most households can capture 60%-70% of their reasonable annual water needs.

The only vulnerability is the dry summers where very little rainfall run-off is available. However, the central fresh water system supplied by the dams would bridge this summer period.

Hypothetically then, if every household supplied at least 50% of its own fresh water needs and practised continued re-use of grey water, then the draw on the main dams could be reduced by, say, 30%-40%. This in turn means that the  water stored in the main dams could last for 3+ years (instead of the present two years) sufficient surely to cope with any ‘normal’ drought. Last but not least, other water production interventions such as water recycling and tapping into underground water would add extra sources that could be variably used from time to time to supplement supplies in times of greater shortage.

The possible outcome?

• Many homes could be transformed into “mini damlets”. At a household level, the cost of doing so should typically be paid back within 3-5 years through saving the costs of water no longer taken from the taps. Savings would naturally continue indefinitely thereafter – suppliers indicate such systems and storage tanks should have a 20+ year lifetime.
• At a city level, it would mean the creation of a water capture and storage system equivalent to building a new dam larger than Wemmershoek for a fraction of what that would otherwise cost. And this collective reduced need for central investment would proportionately grow as the population expanded.
• Many citizens would personally take responsibility for their own water usage and would directly contribute to the management and conservation of water resources. This would support and free the authorities more to concentrate on creating and managing several additional levels of communal water storage, production and distribution.

In so doing greater water security, at both individual household and collective community levels, would be achieved. 

Do take a look this practical example of rainwater harvesting calculated using a real property. Then try calculating it for your own property.

Visit the UCT site to make calculations of your possible rainwater harvesting installations using their easy-to-use “Water Harvesting Tool”. 

Read about a D-i-Y household rainwater harvesting and tank system here

Why else is household-level water harvesting and storage important?

1. It is under your direct control; so you decide:
   • what water to store for which specific purpose.
   • when and how to use or consume that water.
2. You are responsible for the water quality and can maintain your desired standard.
3. Storage investment can be scaled precisely to your household’s ability to harvest water.
4. A properly installed system will be a long-term asset and add to the value of the house.
5. Municipal cost of water and of sewerage is reduced.
6. Your household contributes to stretching the number of days of water stored in the dams.
7. Household’s awareness to save water is maintained, even when rains again fill the dams.

Possible downsides of central (communal) water production facilities.

1. Projects are subject to possible political influences
2. Supply may be diverted for party political and/or corrupt reasons
3. Costs may escalate beyond expectation due to inefficiency and corruption.
4. Budgets may be cut and/or diverted.
5. Once drought is over facilities may be mismanaged and fall into disrepair.
6. Central systems are more easily sabotaged and vulnerable to disaster.

Read here about how to size such a system as well as likely financial benefits that you can enjoy.

Read here how Dani N installed a rainwater capture and tank storage system.