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The link above will lead you to relevant information & video on Micro-dams for rainfall water retention in Central-West Brazil project in Brazil (Link in Portuguese)
Technology of Rainwater Catchment Systems
Damming and Storing of Rainwater in Central Brazil
Luciano Cordoval de Barros
Embrapa Milho e Sorgo
Concerned about the future of water and its quality, the city of Sete Lagoas, in the state of Minas Gerais, has been developing a project for 'Damming and Storing Rainwater.' The system has been in operation for four years in an isolated area. This area covers 70 ha and has 30 small dams.
In 1998 the idea of implementing this system on a major scale became more definite. It was decided to cover the whole micro-area of Ribeirao Paiol with small dams. These small dams were installed in places with heavy rainfall causing erosion. The idea was to block the flow of rain water, minimizing its disastrous effects by keeping out sandy and polluting materials, such as soil, manure, fertilizers and others. These materials tend to go straight to the springs and wells causing condemnation, flooding and other damages.
Like a roof, the soil collects rainwater, concentrating it like a stream; barring it in successive small dams eliminates its damaging effects. After filling the first dam the overflow goes through a drainage ditch to the second dam, and thus on and on until it reaches the valley.
In all of Brazil's middle west the soil is mostly porous and deep. With a rainfall of 1000 to 1600 mm per year, the soil in dammed up areas functions like a storage sponge for filtered water. The main objective of the system is to load and unload the storage pond, adjusting water infiltration in the short time between rains. Much in the same way as numerous drenchings during a rain cycle increase the ground water level, filling the natural water tank of the soil.
The main purpose of the construction of small dams is to recuperate areas devastated by rain and turning spring water into a lasting good water supply. Other objectives are to promote renewal of the valleys, ease small draughts, allow second small harvests and the opening of fish tanks.
English summary:
www.fao.org/ag/agL/watershed/watershed/papers/papercas/paperen/case25en.pdf
More on the topic:
http://www.ircsa.org/9th.html
