Irrigation Development by Inter-basin Water Transfer


Irrigation- Interbasin water transfer

Zambia is generally seen as having the potential of being
able to achieve self-sufficiency in food production and being able to
produce a surplus for meeting shortfalls in Congo DRC, Zimbabwe and
even Kenya. There is virgin land available, without destruction of
rain-forest, and considerable water resources to meet this. However,
to achieve this potential, expansion of irrigation is a must.
Potential for irrigation has been estimated at 410,000 hectares and
our total water resources available would be adequate for this, but
their distribution is lop-sided: the northern half the country has
most of the water, but this goes with poor, leached soils. The best
soils are to be found in the center and southern parts of the country,
where water resources for irrigation are at present short. The total
present flow of the Kafue River is already fully allocated to
generation of electricity and irrigation of sugar cane and Lusaka City
Council; farmers can get water for irrigation only by concession from
ZESCO, whose concern is to keep the maximum of the present flow for
the Kafue Hydro –electric powerhouses. For large-scale agriculture,
the answer is water transfer from the North to the South. Such
transfer appears physically feasible if water is taken from the
Luapula River, across the “Pedicle”, and then directed to the center
and south through the Kafue River.

Transfer would involve a costly civil-engineering mega
scheme, as well as political, international and environmental
challenges. The political challenges include ethnic consideration, in
that the water would come from a Bemba- speaking area and be taken for
use to an area, of Lenje and Tonga-speakers; the international
challenge is that the transfer would be across international
boundaries and of water jointly- owned by Zambia and Congo DRC, and
across Congo DRC land; the environmental challenge would involve the
effect on water levels in Lake Mweru; the civil-engineering challenge
would not be technical (as larger water transfer schemes have already
been done in Libya and elsewhere) but funding.

Since the world-wide challenge is the production of food
for increasing populations, let us assume: that for funding,
assistance from the World Bank is possible; the international
challenges can be resolved by diplomacy/negotiation and the political
one by living up to our national motto of ‘One Zambia One Nation’.

Now as to the technical aspects. Water flows from
Chambesi River basin and the Bangweulu swamps finish up, through the
Luapula River and the Congo, in the Atlantic at Matadi, with very low
utilization for agriculture or industry. The limit to the amount that
can be transferred is dictated, on the one hand, by the lowest flow
recorded at the proposed Intake on the Luapula river and, on the other
hand, by the amount of land economically available for irrigation
close to the Kafue in the center and the south of Zambia. Electric
power in Luapula Province south that can be made available for pumping
is also a limiting factor. Maximum water available for transfer would
be about 90 cubic meters per second. As the transfer is uphill, it
would have to be in a pressurized pipeline. Whether this be in steel
or concrete, the pipes would have to be transported by road and should
be limited in diameter to three meters. This would be adequate for a
transfer rate of 90 cubic meters per second and could irrigate an
additional 90,000 hectares.

If the transfer is aimed to the North Mutondo stream, a
tributary of the Kafue, the distance from the intake works at Chembe
to the boundary and Watershed would be 63km. However, this would
involve a new road system across the pedicle, so it will be more
economic to take the pipeline close to the existing tarred road
despite the increased length to 67 km. The transfer can be taken by a
pipeline- siphon across the hills forming the watershed, involving an
elevation difference of some 295 meters, but it may be worth
considering crossing the watershed through a tunnel and reducing the
elevation difference to 245 meters. Once the water is across the
watershed it can be directed to the North Mutondo stream and flow by
gravity to the Kafue River. The pumping station and intake works
should be on the right bank of the Luapula River for control by
Zambia.

When I was Minister of FOOD & Fisheries in 1992 I initiated a
pre-feasibility study for the project. Government has now declared
irrigation as a development priority. If it is serious about this, it
should now commission a Feasibility Study to produce a bankable
document and proceed to meet the various challenges for its
implementation.

Simon Zukas

Lusaka

Spread the love