This is a good question. Obviously a rainwater tank will not help if there is no rain at all. The thing is that most true drought occur inland whereas most of the population lives near the coast where it does rain. Sure we sometimes have dry seasons where we get below average rainfalls but even if you were to receive half of the average rainfall it should be enough to keep your tanks full for most of the year, if not all of it. This of course depends on the size of your rainwater tank and how much water you use but providing you have a reasonable size tank you should be right.
| Rainfall from 1990 – 1999 In Port Elizabeth | ||||
| 1990 | 441.8 | Avg | 569.41 | |
| 1991 | 451.7 | Lowest | 441.8 | |
| 1992 | 619.5 | Highest | 772.4 | |
| 1993 | 638.7 | |||
| 1994 | 620.3 | |||
| 1995 | 513.1 | |||
| 1996 | 772.4 | |||
| 1997 | 539 | |||
| 1998 | 602.1 | |||
| 1999 | 495.5 | |||
For example, if you live in Port Elizabeth, where water restrictions are amongst the most severe the lowest rainfall in recent years was around 400mm, as shown in the table above for the years from 1990-1999. With a roof harvest area of 200 square metres you would collect around 80 000 litres. Port Elizabeth also has a fairly consistent rainfall throughout the year which is great for regularly topping up you tank. From this figure we can determine that it is enough water to supply half of the average homes’ water requirements! One small rainwater tank of around 500 litres can save around 25 000 litres of water per year. Slimline tanks can easily fit down the side of the house or against a wall so you don’t lose valuable space.
Another question frequently asked: ‘If it rains so much (or at least often enough), then why do we have water restrictions?’
Another good question and quite a detailed one. To put it simply, most of the water we drink is stored in dams and they are, but should not be, the only source of water available to a city. This kind of storage does have a lot to do with drought and rainfall. Catchment areas direct water that lands on the soil and directs it towards the dam. Often these catchment areas are further inland where drought and low rainfall is more common than the coast. If it doesn’t rain then the first rain is soaked up in the soil and does not make it into the dams. If it doesn’t rain again for a while then this process repeats itself. Meanwhile the water is still being consumed and unless decent rain falls then it will simply run out. That’s why it is important to get water tanks so you can take responsibility for your water usage and take pressure of mains supply.
Source: Ezine Articles – Dave C
