Environmental Engineering Reference
In-Depth Information
lymphatic fi lariasis that often increase because reservoirs provide habitat for vectors
(e.g., mosquitoes) and intermediate hosts (e.g., snails). Such investigations will also
help in planning, designing and monitoring future dams.
Gilgel-Gibe hydroelectric dam, created by impounding the water of the Gilgel-
Gibe River in south-western Ethiopia, is currently the largest supply of power (184
MW) in Ethiopia and is operating since 2004. During the construction of the dam,
many people were relocated upstream of the reservoir, although some still remain
close to the buffer zone (500-800 m from the reservoir edge at full supply level) sur-
rounding the lake. The location of the rural villages near the newly formed reservoir
may increase malaria transmission, assuming that this reservoir contributes directly
or indirectly to the presence of breeding places for malaria vectors. Studies in various
African countries indicate that the fl ight range of different species of Anopheles ranges
from 0.8 km (
An. funestus
) [25] to an average of 1-1.6 km (
An. gambiae
s.s) [26], and
the maximum fl ight range of anopheline vector mosquitoes is about 3 km [27-29].
The current study investigates the possible effects of Gilgel-Gibe hydroelectric
dam on malaria transmission and prevalence among children below the age of 10
years, focusing on the distribution of infection in relation to distance of villages from
the reservoir shore. Results may further guide the development of appropriate malaria
interventions for communities living around the reservoir.
MATERIALS AND METHODS
Study Site and Population
The study area is located 260 km south-west of the capital, Addis Ababa in Oromia
Regional State, south-western Ethiopia near Gilgel-Gibe hydroelectric dam. The
study area lies between latitudes 7°42'50''N and 07°53'50''N and between longitudes
37°11'22''E and 37°20'36”E, at an altitude of 1,734-1,864 m above sea level. The area
has a sub-humid, warm to hot climate, receives between 1,300 and 1,800 mm of an-
nual rainfall and has a mean annual temperature of 19°C. The main socio-economic
activities of the local communities are mixed farming involving the cultivation of
staple crops (maize, teff, and sorghum), and cattle and small stock raising. The study
villages are located in Omo-Nada, Kersa, and Tiro-Afeta districts (weredas) and have
similar settlement pattern, have access to health services and are socio-economically
similar. Census results taken between August and September 2005 showed a popula-
tion of 6,985 in the study villages. All the communities residing in the study villages
belong to the Oromo ethnic group, which is one of the largest ethnic groups in Ethiopia.
The reservoir covers an area of 62 km
2
and is located at an altitude of 1,671 m. There
are no other permanent water bodies or impoundments other than the reservoir found
around the 6 study villages.
Study Design
A cross-sectional house-to-house survey was conducted between October and Decem-
ber 2005 in 6 villages located around the reservoir created by the newly constructed
Gilgel-Gibe hydroelectric dam. Sampling was carried out by stratified cluster survey.
Three villages within 3 km of the reservoir (Dogosso, Budo, and Osso) and three villages
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