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Freshwater shortage

The only perennial river, and by far the most dominant source of water
to the Lake (90%) (Cerling 1986), is the Omo River. The Omo River
drainage basin lies mostly within Ethiopia, while the Lake lies within
Kenya. Rainfall in the Lake Basin varies from more than 1500 mm in the
Ethiopian plateau (Halfman & Johnson 1988), to less than 255 mm per
year in the lake area (Survey of Kenya 1977).
The Omo River discharge is about 19 billion m3 of water each year (Beadle 1981).
All the other rivers are seasonal or intermittent, thus there is little overland surface run-off
into the Lake from the surrounding watershed.
The lake water itself is not suitable for drinking due to its high alkalinity
and total dissolved solids concentration (cf. Yuretich & Cerling 1983),
but the affluent river waters and shallow wells along the rivers are used
as sources of potable water. The Turkwel River, entering the Lake from
southwest, was dammed in 1991 for hydroelectric power generation
at Turkwel Gorge, about 150 km west of the Lake. There is
currently no evidence that abstraction of water from aquifers exceeds
natural replenishment. Very little hydrogeological data is available for
effective evaluation in the Lake Basin. Groundwater recharge zones
and amount of groundwater recharge to the Lake are largely unknown.
Nevertheless, on account of the land degradation and increasing
number of settlements, it is likely that the groundwater recharge has,
to some extent, decreased.
Environmental impacts
Modification of stream flow
The freshwater shortage in the Basin is due mainly to modifi cation
of stream fl ow. Along the Omo River in Ethiopia, there has been an
extensive increase in small irrigation schemes diverting water from Lake
Turkana. For example, in the Lower Omo Valley in Ethiopia (rainfall 300
mm/year), fodder and food crop production depends almost entirely
on seasonal fl oodwater from the River Omo and recession farming
in the old river channels (Kay 2001), and the delta (Raymakers 2003).
Alexander (1990, in Haack & Messina 2001) estimates that the Omo
River discharge has been reduced by 50% because of these activities.
Development and commissioning of the large Turkwel River Dam in
1991 has also probably signifi cantly impeded the fl ow of freshwater
in the Turkwel River, and this may have impacted negatively on the
fi sheries in Ferguson’s Gulf through lowered lake levels. Studies are,
however, required to quantitatively determine the environmental
effects of the dam construction.
Pollution of existing supplies
Heavy grazing along the lower Omo valley, especially along watering
routes and overnight pastures, and settlement close to the rivers
indicates that there is some pollution particularly from human
and livestock wastes. In Marsabit District (Kenya), only 5.7% of the
households (1,700 out of 30,000 households) have access to potable
water, and the average distance to the nearest potable water point
is 25 km (Republic of Kenya 2002a). In Turkana District, the situation
is somewhat better, with 28% of households (23,000 out of 80,921
households) having access to potable water, and the average distance
to the nearest potable water point is 10 km (Republic of Kenya 2002b).
Socio-economic impacts
The people in the area are mainly pastoralists, and to a lesser extent,
agro-pastoralists. Most of the lake drainage basin is used as pastureland
(47.5%) compared to only 2.5% used as crop fi elds (World Lakes
Database 2002). The main people affected by freshwater shortage due
to abstraction of water for irrigation, and pollution, would be mainly
those downstream close to the deltas of the Omo and Kerio-Turkwel
Rivers (c f. Raymakers 20 03). The degree of impact to these downstream
users is probably fairly significant, particularly because water abstraction
is a continuous activity, with resultant loss of agricultural uses (crops
and livestock) and productivity, and increased effort to dig more waterwells.
In Africa, nomads have the least access to any health services, and no
satisfactory strategy has been devised to deliver proper health care to
remote populations (Sheik-Mohamed & Velema 1999). Lack of access
to safe water and adequate sanitation remains particularly acute in
rural areas of Ethiopia (CIHI 1996) and Kenya (CIHI 1995) and are major
underlying causes of several diseases. Common diseases related to
quality of water and sanitation include diarrhoeal diseases, intestinal
worms, schistosomiasis, common eye infections such as trachoma,
and skin diseases (CIHI 1996, Republic of Kenya 2002a and b). Most
watering points are, however, along the rivers and the delta area where
permanent settlements and livestock populations are growing. Due
also to lack of health care facilities in this remote region (the average
distance to the nearest health facility in Turkana and Marsabit areas of
Kenya is 50 km and 80 km respectively (Republic of Kenya 2002a and b),
it is expected that more than 25% of the population are affected
by bacterial-related gastroenteritic disorders. The freshwater shortage is
an endemic, age-old situation because of the climatic setting, and the
respective governments are continually making concerted efforts to improve the situation
by digging new wells and boreholes in rural areas, as well as increasing access to piped water
in urban settlements.
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