International Rainwater Catchment Systems Conference
Catchment: An Answer to the Water Scarcity of the Next Millennium."
Petrolina, Brazil - July 1999
Section 4: Technology of Rainwater Catchment Systems
Damming and Storing of Rainwater in Central Brazil
Luciano Cordoval de Barros
Embrapa Milho e Sorgo
Caixa Postal 151, 35701-970 Sete Lagoas, MG, Brasil
Fone: (031) 779.1107
Fax: (031) 779.1088
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
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
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.
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