Using clean irrigation water improves the quality of your crop and your crop yield. Furthermore, the usage of good quality water is of high importance for your post harvest water. It lengthens the vase life considerably. However, on our continent water is most of the time not available in quantities that are needed for a healthy crop, not to speak of obtaining water that is of a constant quality.
Water is a many sided product. Substances dissolve in water, and countless (micro) organisms grow in water. The treatment of the different sorts of water demands different technologies. Furthermore, each local situation requires its own individual solution. In this article we tried to outline the possibilities for the provision of water for small scale projects. Obviously, one of your goals is an optimum crop yield. Costs, quality and availability have always to be taken into account. Whether you will harvest rainwater or want to go that extra mile. At all times, water efficiency is highly important.
Availability, costs and required quality will always be on the bases of the decision what water provision to rely on. What are the possibilities for your water provision?
Rainwater is excellent to use as irrigation water or post harvest water for small scale water projects. It is easily collected in basins, but unpredictable weather circumstances make it difficult to rely on it as your only source of water. Furthermore, water deteriorates quickly. To ensure a stable quality of your water, you still have to conserve and treat before use. Filtration is most widely used
Lake or river water
When you have the luxury to be stationed in the vicinity of a lake or river, you can consider using that water. Transport costs will be low, but the quality of the water will vary fairly. As a consequence, the water will need treatment depending on the contamination of the water (and features of the lake): innumerable organisms grow in water.
To lake and river water filtering and disinfection technologies have to be applied or chemicals have to be added to destroy unwanted organisms that can ruin your crop. Treatment will be necessary to conserve and maximize the crop yield. As the quality of the feed water varies tremendously, samples have to be taken continuously and the appropriate treatment has to be adjusted according to the results of the analysis every time, which makes it very time consuming. Often multimedia filtration and UV disinfection shall be a necessary treatment for this water.
Borehole water (well water)
To overcome the dry season or when there is a shortage of water you can also use borehole water. This will ensure that you always have an adequate supply of both irrigation and post harvest water. Another advantage is that it is of a constant high quality. For this, you use borehole water. As this water is often too saline for irrigation purposes, you need to treat it with reverse osmosis (RO) membrane filtration. With this desalination step, most of the substances present in the water are separated by membrane filtration. To prevent the membranes from fouling a pre filtration has to be applied. The optimum pre filtration set up depends on the specific feed water quality and the situation at the project location (climate, local skills etc). E.g. cyclone / multimedia / cartridge filtration.
A borehole must be made by a professional drilling company. Depending on layers they can determine exact place and depth. The quality of the bore hole water is leading for the design of a reverse osmosis system. The choice of components depends directly on the different ions and impurities in the water. Furthermore the desired quantity and quality are main items of an inventory that should be made before a well informed choice can be made.
The treatment of the different sorts of water demands different technologies and products. To name but a few: filtration, desalination (reverse osmosis), (UV) disinfection. Solutions are possible, from low to high tech, but of course financial boundaries have to be known.