Water Resource Potential Evaluation of Berga River Catchment, West Shewa Zone, Oromiya Regional State
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Date
2006-06
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Addis Ababa Universty
Abstract
Berga river catchment is located in west part of Addis Abeba with SW to NE stretch
of 8057'58" N to 9018'35" N latitude and 38020'49" E to 38029'33" E longitude. It is a
sub-catchment of Awash basin, found at water divide of Awash and Abbay drainage
basins. It has a total area of 303km2.
The study area is characterized by irregular undulated physiographic features. The
main rocks in the catchment are basalt, ignimbrite, trachytes/rhyolites and alluvial
deposits.
From long term mean monthly meteorological data, the catchment has 1119.26mm,
898.68mm, and 664.25mm annual rain fall, potential evapotranspiration and actual
evapotranspiration respectively. The estimated annual relative humidity, wind speed
at 2m above the ground, sunshine hour, and temperature range are 64.4%, 1.64m/s,
6.5hr/day, and 14.05―16.73Oc respectively. 92.73 million Cubic meter water leaves
the catchment annually in the form of river flow (runoff).
The main aquifer in the catchment is weathered and fractured basalt. From borehole
log, and field observation of hand dug wells and springs, in low land parts of Berga
river catchment 3—15m depth is potential for hand dug well(except at Kimoye site)
and shallow groundwater. This area is also potential for borehole with maximum
depth of 150m. At present, the most available water source in the catchment is
springs and streams. Ignimbrite, rhyolite/trachyte are aquifers with moderate to low
ground water potential zone. 82.71mm water is used to recharge groundwater
reservoir annually.
Ground water is generally a localized flow system controlled by topography and
geology. Water in the catchment is mainly of Ca-Mg-HCO3 and Ca-Na- HCO3 type.
Almost all water in the study area are hard to very hard and TDS is generally below 480mg/l. the sum of Ca2+ and Mg2+ is grater than the sum of Na+ and K+ in all water
sources.
All water in the catchment is fresh which is suitable for almost all purposes. Almost
all parameters are with in the limits of acceptable values of WHO and Ethiopian
water quality standard/guide line except some hand dug wells showing bacterial
pollution.
Description
Keywords
Berga River Catchment, Berga River Catchment