This is the VOA SpecialEnglish Development Report.
Safe drinking water has always been rare and valuable. Throughoutthe world, drinking water has to be stored for periods of lowrainfall. Tanks or other containers for water storage must be readylong before a dry season begins.
For hundreds of years different kinds of materials have been usedto build water storage containers. In many areas of the world, smalllakes or reservoirs formed by dirt walls provide drinking water forvillagers during the long dry season. In western Sudan, the thickpart of the baobob tree is removed to store water collected duringthe short rainy season in that country.
Bricks and concrete are among the modern materials used today tobuild storage containers for water. A solid rock can be used as thebottom of a water tank. However, a mixture of rock and soil shouldnot be used. The soil will settle down, but the rock will not. Thewater will leak out.
Ferro-cement structures are popular in some developing countries,especially in India. Ferro-cement is made by pouring a sand andcement mixture over a skeleton form made of steel rods, pipe, orchicken wire. It creates a structure that is lightweight yet keepsin water. The walls of ferro-cement structures are usually thin,which means that they can be used in building different shapes suchas circles.
Wood also can be used for water storage structures. Cypress, fir,pine and redwood are some of the kinds of trees that have been used.Wooden tanks do not require special care, although their averagelifetime is shorter than tanks made with concrete or steel. Anychemicals used to keep the wood from being ruined must not bepoisonous substances.
Water in uncovered storage tanks or reservoirs can become unsafe.Small green plants called algae can grow in large amounts near thesurface. The algae may help bacteria continue to grow, even ifchemicals such as chlorine are added to the water to kill thebacteria. Uncovered water also can be polluted by birds, animals orhumans.
You can learn more about storing water for drinking through theVolunteers in Technical Assistance, or VITA. VITA is on the Internetat www.vita.org.
This VOA Special English Development Report was written by GaryGarriott.