Geoscience Reference
In-Depth Information
Flow for a normal year: Site 3 Mara River, Tanzania Border
Present Day
45
Recommended (BF+Floods)
40
Recommended Base Flow (BF)
35
30
25
20
Figure 4.2
Monthly flows
recommended for the reserve
(environmental flows,
sensu
Government of Kenya, 2002) during a
'normal' year (not very wet or dry), in
theMaraRiver,atsite3onthe
Kenya-Tanzania border (Modified
from WWF-TCO, 2010).
15
10
5
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
escarpment in Kenya, from natural forest that has
been cleared extensively in the past 15 years,
through irrigated farmland, the extensive grazing
lands of the Masai, into the iconic Masai Mara
(Kenya) and Serengeti (Tanzania) conservation
areas. The river provides the only perennial water
in these conservation areas, from which it flows in
a westerly direction, through extensive wetlands,
into Lake Victoria at Musoma. The river flows
have been modified by erosion and deforestation,
irrigation abstraction, and are threatened by plans
for further abstraction and inter-basin transfer. All
of these emanate from the upper Kenyan parts of
the basin. Additional modifications, particularly to
water quality, arise from the increasing number of
tourist lodges, camps and hotels which use water
from the river, and dispose of their waste water
back into it.
Despite this, the flows are not impounded
substantially, and the flow patterns remain largely
natural, apart from reduced low flows, particularly
during droughts. A team of Kenyan and Tanzanian
specialists, contracted by WWF East Africa and
the US Global Water for Sustainability Programme
(GLOWS), conducted a two-year assessment of
the flows required to maintain the river in a
near-natural state, facilitated by UNESCO-IHE.
The results indicated that, at the environmental
flow site on the Kenya/Tanzania border, flows
amounting to 35% of the average flow recorded
over the 26 years on record would be sufficient to
achieve this objective (LVBC and WWF-ESARPO,
2010) (Figure 4.2). Of course, these are preliminary
predictions, with some uncertainty involved, but
they indicate that there can still be economic
development of the water resources of the Mara
River, without degrading unacceptably the natural
resources of the basin. In the dry season during
drought years there is already a deficit of the
required flows, so that some storage or demand
management would be required during these
periods. Additional assessments need to be carried
out for the downstream reaches of the river,
including the Tanzanian wetlands and the inflows
to Lake Victoria. With these caveats, the project
demonstrated that:
Environmental flows should ideally be carried
out before the water resources of a river
are allocated substantially. They can then be
incorporated in the future plans for development
of the river.
So far from preventing further development,
such an assessment can demonstrate that
there is potential for further consumptive
use, without unacceptable degradation of
the
resources.
