International Rainwater Catchment Systems Conference
Mannheim, Germany - September 2001
Rainwater Catchment in Humid and Arid Regions
Rainwater Harvesting with Subsurface and Sand Dams
Ethiopia has a yearly surface water potential of 110 billion cubic meter
coupled with an estimated groundwater resource of over 2.6 billion cubic
meter. One way or another these water resources are derived from a yearly
rainfall. The great diversity in geography associated with high rugged
mountains, flat topped plateaus, deep gorges and the extreme variation
in altitude ranging from an area of below sea level to peaks reaching
over 4,500 meters result with high variation in annual rainfall ranging
between 200 to 2000 mm per year.
The present coverage of water supply of the country is about 17%. Given
the current population of about 60 million accompanied by annual growth
rate of over 3% with incompatible economic development, it is unlikely
that substantial improvement in the water supply coverage will be attained
within a foreseeable future.
Even though rainwater harvesting ranks high on the priority list as
a cheap possibility to alleviate the severe drinking water shortage, roof
water catchment is not popular in the country, particularly in the rural
areas, since the vast majority of the residential houses have thatched
roofs, not suitable for rainwater collection, and the high costs of the
water storage facilities.
Ponds are the most prevalent means of rainwater harvesting in rural
areas of Ethiopia. In the Gambella region for instance, over 30% of the
water supply for drinking purpose comes from ponds. They are also very
common in the arid and semiarid parts of the country where alternative
water sources are not available. These ponds are planned, constructed
and managed by the communities.
Besides its high turbidity and bacteriological load, the water stored
in the ponds is not available all year round due to water loss through
seepage, sediment deposit and evaporation. Apart from natural self-purification,
the ponds do not have any sort of water treatment facilities and improved
water abstraction mechanisms. Due to the unsanitary situation around the
ponds, they create conducive breeding areas for mosquitoes as well as
for spreading of water borne diseases.
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