Don’t let rainwater run away; use these techniques to effectively collect water from your own roof. Usually, large roof surfaces are equipped with gutters and down-pipes.
These features only require the construction of a simple storage structure to collect the rainwater that would normally go to waste if not caught for later use. If small roof surfaces are not equipped with gutters, the following cheap and easy solution can be implemented to collect rainwater (see Figure 1 for an example).
Using a proper lining will make it easier to store water in earth dams.
A 50 mm diameter polythene pipe or something similar can be used. A slit should be cut lengthwise into the pipe to split it in half. Measure it to have the cut part as long as the roof. Wire can then be used to secure the pipe in place on the roof plates or rafters so that it can successfully collect the water running down from the roof. The same pipe can be used as a down-pipe into the water collecting container, by making the end of the pipe that is not tied and cut in half as long as possible (see Figure 1). You can also use a 90-degree fitting to let the pipe run down straight at the corner.
Figure 1: Gutter of polythene pipe for small tin roofs.
Harvesting water from thatched roofs
Collecting water from a thatched roof will require the use of small pieces of corrugated iron sheets. It should be well secured under the edge of the thatched roof so that it protrudes out by approximately 300 mm and in such a way that the water running down from the roof can be collected on the metal roof sheets.
The entire roof’s edge should be equipped with these corrugated sheets. This process is nearly identical to the tin roof and polythene pipes, because it uses similar installation steps (see Figure 2 for an example).
Harvesting water from ground surface or stone slabs
Ground surfaces that have been properly prepared with a reasonable slope will ensure the rapid run-off of surface rainwater.
To improve the run-off if the soil is not compact enough or does not have a hard texture, you can do the following:
- Remove unnecessary vegetation, level the surface, and compact the soil with a roller.
- Use the soil and cement combination method for firmly compacted soil.
- Prevent the growth of vegetation and build weirs to guide the water to the storage reservoir.
- It is possible to collect water from big granite boulders or stone slabs. Water can be transported to a reservoir via a pipe because of the high run-off produced by these features. If natural run-off patterns occur on rocks, a weir can be built to collect the water and store it for later use. (See Figure 3 for an example).
Figure 2: Method of water harvesting from thatched roofs.
Figure 3: Dams on rock slabs.
The information provided in this article is credited to the Institute of the Agricultural Research Council (ARC). For more information, visit their website at www.arc.agric.za, contact them on +27-12-842-4000 or send an e-mail to iae@ing1.agric.za.
