10th International Rainwater Catchment Systems Conference
"Rainwater International 2001"
Mannheim, Germany - September 2001

Section 2: Rainwater Catchment in Humid and Arid Regions

Paper 2.6

Rainwater Harvesting with Subsurface and Sand Dams

Mesfin Shenkut
Ethiopia
email: ayeu-shashe@telecom.net.et

Introduction

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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