Dam Synchronisation and Flood Releases - agriwaterpedia.info

DAM SYNCHRONISATION AND FLOOD RELEASES IN THE ZAMBEZI RIVER BASIN: ANNEX 4 OF FINAL REPORT
2 Regulation of Shire River and Lake Malawi
2.1 Introduction to the investments
The regulation or blocking of the Shire River flows changes the regimes of downstream flows
and water levels as well as the upstream lake levels. This could have positive or negative impacts
which may influence the occurrence of floods as well as the conservation and utilization of
ecosystem and the utilization of water by different water users. This has been the topic of study
in Annex 2 Concepts and Recommendations for Dam Management and for further detail
reference is made to this Annex.
The proposed investments for Shire River flow regulation identified in the ToRs are:
the upgrading of Kamuzu Barrage which would increase the operating level of the Kamuzu
barrage and improve possibilities for operation; and
the pumping scheme at Mponda, that would allow for pumping water from Lake Malawi
whenever the lake levels are too low to allow adequate outflow.
Besides, there are additional plans for:
Kholombidzo on the Shire River, which will also be discussed in this Chapter.
In January 2011 a call for interest for an integrated flood and drought risk management plan for
the Shire basin in Malawi has been advertised. This plan will study in more detail different
options available for flood protection. An environmental impact assessment on the upgrading of
the Kamuzu Barrage is currently being carried out.
2.2 Situation assessment: stakeholders views and expert views
The Ministry of Water in Malawi (interview August 2010) has a few strongly held views with
regards to the regulation of the Shire River and Lake Malawi:
Kamuzu Barrage was never designed for flood control and therefore evaluation of the
Upgrading of Kamuzu Barrage should not concentrate on flood control; flood regulation
from the main tributaries is more important to prevent flood damage in the lower Shire;
Subsistence farming in the floodplains appears to have increased erosion and siltation of the
Shire River and has also increased flood risks because of the presence of people and their
livelihood in the floodplain. However, subsistence farming in the flood plains is something
which should be accommodated due to scarcity of arable land and assistance should be
provided to make it sustainable; and
Improved flow forecasting, in particular from the Zambezi and from the Shire tributaries,
can help in flood risk management in the Shire system.
ESCOM Malawi (interview and site visits, August 2010) also made clear that:
Floods do not damage the Shire power stations, but water hammering due to late switching
off of power stations can cause damage. Tedzani I and II power stations (40 MW) were out
of commission from 2001 till 2007 due to the water hammer related damages to the turbines.
The rehabilitation of these power stations started in 2006 and was completed end of 2007, at
a cost of US$12.24 million (estimate 2005). Better monitoring and forecasting of weed
clogging is being implemented and this prevents damage. (See for further detail Annex 2,
Chapter 6);
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