Predictings sediment loading into Masinga reservoir and its storage capacity reduction
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Date
2005-09-07Author
Mutua, Benedict M.
Klik, Andreas
Loiskandl, Willibald
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Show full item recordAbstract
It is estimated that the annual loss in storage capacity of the world’s
reservoirs due to sedimentation is around 0.5 – 1.0%. For many reservoirs,
however, annual depletion rates are much higher and can go up to 4% or 5%,
such that they lose the majority of their capacity after only 25 – 30 years. The
Masinga reservoir, one of the main reservoirs in Kenya, designed for hydropower
generation, public water supply and irrigation is faced with severe sedimentation.
The designed sediment load into this reservoir in 1981 was estimated to be 3.0 x
106
m3
per year (about 1% per annum reservoir reduction). By 2000, annual
sediment loading had increased to over 11.0 x 106
m3
, nearly four times, thus
reducing the designed capacity by more than 15%. As land degradation has
become more evident with increasing land use change within Masinga catchment
over the years, the operation and life span of Masinga reservoir is thus under
imminent danger from erosion and sedimentation. There is need therefore to
quantify spatially soil erosion and sediment yield reaching the reservoir with a
view to reducing the sediment delivery. In this paper, a comprehensive procedure
to predict spatial sediment yield and overall mean annual sediment volume
delivered to Masinga reservoir is presented. Geographical Information System
(GIS) technology as a tool to support soil erosion and sediment models is
employed. Simulations of different land use and management scenarios are
performed and their corresponding sediment yields estimated. Predictions show
annual sediment loading into the reservoir of about 14.0 x 106 m3
for land use
practices in 2003. By simulating the best feasible management practices (BMPs),
the achieved results show that the sediment volume reaching the reservoir could
be reduced to about 6.0 x 106
m3
per year.
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