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Study Name:
Orange River Integrated Water Resources Management Plan
Report Title:
Water Quality in the Orange River
Submitted By: WRP Consulting Engineers, Jeffares and Green, Sechaba Consulting, WCE Pty Ltd,
Water Surveys Botswana (Pty) Ltd
Authors:
L Hattingh
Date of Issue: October 2008
Distribution:
Botswana: DWA: 2 copies (Katai, Setloboko)
Lesotho: Commissioner of Water: 2 copies (Ramosoeu, Nthathakane)
Namibia: MAWRD: 2 copies (Amakali)
South Africa: DWAF: 2 copies (Pyke, van Niekerk)
GTZ: 2 copies (Vogel, Mpho)
Reports:
Review of Existing Infrastructure in the Orange River Catchment
Review of Surface Hydrology in the Orange River Catchment
Flood Management Evaluation of the Orange River
Review of Groundwater Resources in the Orange River Catchment
Environmental Considerations Pertaining to the Orange River
Summary of Water Requirements from the Orange River
Water Quality in the Orange River
Demographic and Economic Activity in the four Orange Basin States
Current Analytical Methods and Technical Capacity of the four Orange Basin States
Institutional Structures in the four Orange Basin States
Legislation and Legal Issues Surrounding the Orange River Catchment
Summary Report

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TABLE OF CONTENTS
1
INTRODUCTION ..................................................................................................................... 4
1.1 General ......................................................................................................................... 4
1.2 Objective of the study ................................................................................................... 9
1.3 Purpose and structure of report ................................................................................. 11
2
AREAS PRONE TO FLOODING ON A GLOBAL SCALE.................................................... 12
2.1 Botswana .................................................................................................................... 12
2.2 Lesotho ....................................................................................................................... 12
2.3 Namibia....................................................................................................................... 12
2.4 South Africa ................................................................................................................ 12
3
FLOOD FORECASTING CAPABILITIES ............................................................................. 14
3.1 Botswana .................................................................................................................... 14
3.2 Lesotho ....................................................................................................................... 14
3.3 Namibia....................................................................................................................... 14
3.4 South Africa ................................................................................................................ 15
4
FLOOD CONTROL WORKS................................................................................................. 16
4.1 Botswana .................................................................................................................... 16
4.2 Lesotho ....................................................................................................................... 16
4.3 Namibia....................................................................................................................... 16
4.4 South Africa ................................................................................................................ 17
5
RESERVOIR OPERATING STRATEGIES FOR ALL MAJOR RESERVOIRS.................... 20
5.1 Botswana .................................................................................................................... 20
5.2 Lesotho ....................................................................................................................... 20
5.3 Namibia....................................................................................................................... 20
5.4 South Africa ................................................................................................................ 21
6
EXISTING DISASTER MANAGEMENT STRATEGIES ....................................................... 23
6.1 Botswana .................................................................................................................... 23
6.2 Lesotho ....................................................................................................................... 23

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6.3 Namibia....................................................................................................................... 24
6.4 South Africa ................................................................................................................ 24
7
CONCLUSIONS AND RECOMMENDATIONS .................................................................... 25
7.1 Conclusions ................................................................................................................ 25
7.2 Recommendations...................................................................................................... 25
8
REFERENCES ...................................................................................................................... 27
LIST OF FIGURES AND TABLES
Figure 1-1: Orange River................................................................................................................. 4
Figure 1-2: Approximate Water Balance for Natural Runoff in the Orange River Basin................ 5
Table 1.1: Orange River Water Balance at 2005 Development Level ........................................... 6
Figure 1-3: Major Water Demands along the Lower Orange River................................................ 7
Figure 1-4: Major Water Transfer Schemes from Gariep and Vanderkloof dams. ........................ 8
Figure 1-5: Phase 1 of the Lesotho Highlands Water Project. ....................................................... 9

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1
INTRODUCTION
1.1
General
The Orange River originates in the Lesotho Highlands and flows in a westerly direction
2 200 km to the west coast where the river discharges into the Atlantic Ocean (see
Figure 1-1). The Orange River basin is one of the largest river basins south of the
Zambezi with a catchment area of approximately 0.9 million km2.
Figure 1-1: Orange River
It has been estimated that the natural runoff of the Orange River basin is in the order of
11 600 million m3/a of which approximately 4 000 million m3/a originates in the Lesotho
Highlands
and
approximately
900 million m3/a
from
the
contributing
catchment
downstream of the Orange/Vaal confluence which includes part of Namibia and a small
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portion in Botswana feeding the Nossob and Molopo rivers. Whether or not these two
rivers directly contribute to the Orange River is an outstanding issue which will be
addressed during the study. The remaining 6 700 million m3/a originates from the areas
contributing to the Vaal, Caledon, Kraai and Middle Orange rivers.
It should be noted that much of the runoff originating from the Orange River downstream of
the Orange Vaal confluence is highly erratic (coefficient of variability greater than 2) and
cannot be relied upon to support the various downstream demands unless further storage
is provided.
Figure 1-2: Approximate Water Balance for Natural Runoff in the Orange River Basin
The water flowing into the Orange River from the Fish River in Namibia (near the river
mouth) could theoretically be used to support some of the downstream demands,
particularly the environmental demands at the river mouth.
To date, however, the
contributions from the Fish River (in Namibia) cannot be utilised to support any
downstream demands since these demands are currently supplied with water from
Vanderkloof Dam which must be released well in advance since the water takes 2 to 6
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weeks to reach the mouth (some 1 400 km away). Any water flowing into the Orange
River from the Namibian Fish River will therefore add to the water already released from
Vanderkloof Dam since it is currently not possible to stop or store the additional water
once it has been released.
The figures indicated in Figure 1.2 refer to the natural runoff which would have occurred
had there been no developments in the catchment. The actual runoff reaching the river
mouth (estimated to be in the order of 5 500 million m3/annum) is considerably less than
the natural value (over 11 000 million m3/annum). The difference is due mainly to the
extensive water utilisation in the Vaal River basin, most of which is for domestic and
industrial purposes.
Large volumes of water are also used to support the extensive
irrigation (estimated to be in the order of 1 800 million m3/annum) and some mining
demands (approximately 40 million m3/annum) occurring along the Orange River
downstream of the Orange/Vaal confluence as well as some irrigation in the Lower Vaal
catchment and Eastern Cape area supplied through the Orange/Fish Canal. In addition to
the water demands mentioned above, evaporation losses from the Orange River and the
associated riparian vegetation account for between 500 million m3/a and 1 000 million m3/a
depending upon the flow of water (and consequently the surface area) in the river
(Mckenzie et al, 1993, 1994 and 1995). An approximate water balance for the Orange
River is given in Table 1-1 to provide perspective on the various demands supported from
the river.
Table 1.1: Orange River Water Balance at 2005 Development Level
Water Balance Component
Volume (million m³/a)
Environmental Requirement
(1)
900
Namibia
(2)
120
Lesotho & Transfers to RSA
(3)
820
RSA Orange River Demand
(4)
2 560
RSA Vaal River Demand
(5)
1 560
Evaporation & losses
(6)
1 750
Spillage
(7)
3 780
Total
11 490
Spillage under natural conditions
10 900
Notes
(1) - Includes natural evaporation losses from Orange River.
(2) - Includes water use from Orange & Fish rivers.
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(3) ­ With Full Phase 1 of LHWP active.
(4) ­ Includes transfers to the Eastern Cape.
(5) ­ Vaal Demand supplied from locally generated runoff.
(6) ­ Excludes evaporation losses from the as it is already included in component 1.
(7) ­ Average spillage at 2005 development level
Several new developments have already been commissioned or have been identified as
possible future demand centres for water along the Lower Orange River. In Namibia such
developments include the Haib copper mine, Skorpion lead and zinc mine (already
developed), the Kudu gas fired power station at Oranjemund and several irrigation projects
for communal and commercial irrigation along the northern riverbank. Similar potential
also exists on the South African side of the river with particular need to develop irrigation
for previously disadvantaged farmers.
In Lesotho there is considerable development
planned for the Lesotho Lowlands area and also the potential for further transfers from the
Lesotho Highlands Water Project. In Botswana, the developments that may influence the
Orange River are restricted mainly to groundwater abstraction.
Figure 1-3: Major Water Demands along the Lower Orange River.
In Lesotho, the first phase of the Lesotho Highlands Water Project was recently completed
and represents one of the largest water transfer schemes in the world. Some details of the
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scheme are shown in Figure 1-5. It should be noted that the water transfers shown in the
figure are approximate values only and are likely to change due to revision of
environmental requirements etc.
Figure 1-4: Major Water Transfer Schemes from Gariep and Vanderkloof dams.
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Figure 1-5: Phase 1 of the Lesotho Highlands Water Project.
1.2
Objective of the study
In view of the existing and possible future developments which will influence the availability
of water in the Orange River, a project has been initiated by ORASECOM and
commissioned and funded by GTZ involving all four basin states (Botswana, Lesotho,
Namibia and South Africa. The main objective of the project is to facilitate the development
of an Integrated Water Resources Management Plan for the Orange River Basin. The plan
will in turn facilitate the following specific objectives:
· Maximise benefits to be gained from Orange River water;
· Harmonise developments and operating rules;
· Foster peace in the region and prevention of conflict;
· Encourage proper and effective disaster management;
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· Ensure that developments are sustainable and encourage the maintenance of
bio-diversity in the basin, and
· Management of potential negative impacts of current and possible future
developments.
In order to achieve the above objective it is envisaged that the resulting Water Resources
Development Plan will be founded on the following four basic principles:
· Reasonable utilisation of available water resources;
· Equitable accrual of benefits to basin states;
· Sustainable utilisation of water resources, and
· Minimisation of harm to the environment.
The strategy to be adopted by the project team to meet the objectives should involve the
following:
· Sharing of information on existing and proposed future developments;
· Facilitation of a common understanding of key issues based on comparable
technical and institutional capacity;
· Development of comparable legislation and institutional structures;
· Adoption of comparable standards and management approaches;
· The development of a Water Resource Management Plan for the future
development and management of the water resources of the Orange River.
It is anticipated that the development of the Water Resource Management Plan will be
undertaken in phases and the remainder of this document refers to the work involved with
Phase 1 of the project. Phase 1 will involve the following:
· A desktop study to establish the status quo within the basin and to create an
agreed base from which the subsequent phases of the project can be developed;
· To facilitate capacity building where possible in order to strengthen expertise
throughout the four basin states;
· To identify and highlight deficiencies in the knowledge base which must be
addressed before the Water Resource Management Plan can be finalised. Some
fieldwork may be required in subsequent phases of the project;
· To develop a preliminary Water Resource Management Plan which can be used
as the basis from which the final plan can ultimately be developed;
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· To develop a draft scope of work for subsequent phases of the project from which
a Terms of Reference can be developed by the Client.
An inaugural meeting to discuss the project and in particular the expected content for the
Inception Report was held in Botswana on 8 February 2004.
1.3
Purpose and structure of report
The purpose of this report is to establish the status quo of flood disaster management in
the Orange River catchment on a reconnaissance level and to make recommendations
regarding gaps and possible improvements.
This document includes a brief overview of the areas prone to flooding in Section 2.
Section 3 then provides a brief description of the flood forecasting capabilities for the
Orange River Basin while Section 4 and 5 provides an overview of the flood control works
and the reservoir operating strategies for all major reservoirs respectively. Finally,
Section 6 provides an overview of existing disaster management strategies.
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2
AREAS PRONE TO FLOODING ON A GLOBAL SCALE
The areas that are prone to flooding can be divided in two distinct categories, namely
those with human settlement areas (settlements, towns, cities) where flooding can lead to
loss of life and direct and indirect financial, social, socio-economic and environmental
impacts and irrigation farmland where flooding normally leads to direct and indirect
financial, social, socio-economic
and
environmental impacts (see Figure A-1 in
Appendix A for the location of the major human settlement areas prone to flooding).
It is also important to note that Task 3 (ORASECOM: 2007) summarises the physical
characteristics of the various existing water resources infrastructure (including dams and
irrigation schemes) and these characteristics will not be repeated in this report.
2.1
Botswana
On a global scale no human settlement or irrigation farmland are threatened as a result of
being close to a major river in the Orange River Basin in Botswana.
2.2
Lesotho
The large majority of habitation as well as farming take place in the lowlands in Lesotho
(the Caledon catchment). These lowlands are also prone to frequent flooding resulting in
the occasional loss of life as well as frequent loss of agricultural production.
2.3
Namibia
The area downstream of Hardap Dam (in particular Mariental town, the Hardap irrigation
scheme as well as the major north-south road network) is prone to frequent flooding. It is
also important to note that the irrigation areas on the banks of the Orange River are also
prone to flooding. After the 2006 flood event an investigation has lead to a decision to
raise Hardap Dam to increase its attenuation capacity, to construct a levy system around
Mariental town for protection and to clean excess vegetation (reeds) from the river
channel.
2.4
South Africa
It is important to note that Emergency Preparedness Plans should exist for the area
downstream of each dam classified to have a safety risk according to Dam safety
legislation. These plans in general include an inundation map of the dam break flood.
There is, however, still a large percentage of required Emergency Preparedness Plans
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outstanding. It is recommended that these plans be completed as a matter of urgency.
2.4.1
Vaal River System
The main human settlement areas in the Vaal River System prone to flooding are
downstream of Grootdraai Dam and Vaal Dam respectively and include towns like
Standerton, Vereeniging and Parys. Most of the formal irrigation schemes in this system
are situated close to the main rivers and are therefore also prone to flood damage.
A detail inundation map has also been developed for the main stem of the Vaal River from
Vaal Dam to the confluence of the Vaal River and the Orange River for different flood
sizes.
2.4.2
Upper Orange System (excluding Lesotho)
Except for Aliwal North and Hopetown on the banks of the Orange River and Wepener on
the banks of the Caledon River, no other major human settlement is located close to a
main river. It is interesting to note that a section of Wepener was relocated as a result of
flooding due to the backwater effect of the siltation of Welbedacht dam. Most of the formal
irrigation schemes in this system are situated close to the main rivers and are therefore
also prone to flood damage.
2.4.3
Lower Orange River System
The main human settlement areas in the Lower Orange River System around especially
Upington, Prieska, Keimoes and Kakamas are prone to flooding. Most of the formal
irrigation schemes in this system are situated close to the main stem of the Orange River
and are therefore also prone to flood damage.
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3
FLOOD FORECASTING CAPABILITIES
It is important to note that the South African Development Community has a co-ordinated
initiative
called
"Regional
Flood
Watch"
that
is
available
on
its
website
(http://www.sadc.int/floods/rfw.php). It summarises flood and rainfall information from a
large number of both international and local information sources and provide a country
view where necessary.
3.1
Botswana
The Botswana Department of Meteorological Services (http://www.weather.info.bw/)
provides a number of rainfall forecasting services in association with the US National
Oceanic and Atmospheric Administration as well as the South African Weather Service. It
can in general be categorised as long and short to medium term forecasts and are focused
primarily on aviation and agriculture. The long-term forecast normally takes the form of a
pre-season assessment while the short to medium term forecasts takes the form of rainfall
forecasts using mathematical models, satellite and radar information.
3.2
Lesotho
Similar
to
its
Botswana
counterpart,
the
Lesotho
Meteorological
Services
(http://www.lesmet.org.ls/) provides a number of rainfall forecasting services. It can in
general be categorised as long and short to medium term forecasts and are also focused
primarily on aviation and agriculture. The long-term forecast normally takes the form of a
pre-season assessment while the short to medium term forecasts takes the form of rainfall
forecasts using mathematical models and satellite imagery.
3.3
Namibia
The Namibia Meteorological Service (NMS) (http://www.meteona.com/) provides a number
of rainfall forecasting services which can possibly be used as early flood warning. It can in
general be categorised as long and short to medium term forecasts. The long-term
forecast normally takes the form of a pre-season assessment while the short to medium
term forecasts takes the form of rainfall forecasts using mathematical models. It is
recommended that the accuracy of the NMS short term prediction models should be tested
independently over a period of a couple of years before a final decision is made regarding
its applicability in operational decision-making.
In addition to rain forecasting, use are also made of a rainfall and water level monitoring
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system by Namwater as well as rain gauging by NMS during rainfall events to determine
the extent and magnitude of the event.
The NMS was planning to construct a radar system at Windhoek for rainfall prediction as
well as monitoring purposes. It was planned that the range of the station would include the
Hardap catchment and possible also the catchment downstream of Hardap Dam that joins
the Fish before Mariental town. This station has subsequently been put on ice. It is
recommended that the feasibility and implementation of such a station be investigated.
3.4
South Africa
The South African Weather Service (SAWS) (http://www.weathersa.co.za/) provides a
number of rainfall forecasting services which are used as early flood warning. It can in
general be categorised as long and short to medium term forecasts. The long-term
forecast normally takes the form of a pre-season assessment while the short to medium
term forecasts takes the form of rainfall forecasts using mathematical models using
information from satellites as well as radar.
In addition to rainfall forecasting by SAWS, use are also made of a rainfall and water level
monitoring system by the South African Department of Water Affairs and Forestry (DWAF)
as well as rain gauging by SAWS during rainfall events to determine the extent and
magnitude of the event.
Interviews with officials representing entities within DWAF highlighted the following general
problems with respect to flood forecasting capabilities:
· A decreasing number of operational rainfall gauging stations;
· Vandalism of gauging station equipment, especially solar panels and cellular
modems;
· An insufficient number of real-time flow gauging stations, both in controlled and
uncontrolled water management systems;
· Most flow gauges are designed for low flow conditions and not to cope with
extreme floods;
· Communication problems in floods situations;
· Existing rainfall-runoff forecasting models need improvement;
· Inadequate manpower available for operational and flood documenting
functions; and
· Limited flood line analyses information available for hazard determination.
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4
FLOOD CONTROL WORKS
No specific structures exist in the Orange River Basin that was specifically constructed for
flood control. Dams, however, in general have an attenuating effect on floods. The
attenuation of a flood is directly related to size of the storage capacity of the reservoir of a
dam (the larger the capacity the more attenuation of a flood would take place). Dams with
gated spillways, however, can be operated differently depending on the size on the
incoming flood. In the remainder of the chapter the existence of dams with significant
storage especially those dams with gated spillways will be discussed in more detail (see
Figure A-1 in Appendix A for the location of the major dams as well as whether they have
uncontrolled or gated spillways).
It is also important to note that Task 3 (ORASECOM: 2007) summarises the physical
characteristics of the various existing water resources infrastructure (including dams) and
these characteristics will not be repeated in this report.
4.1
Botswana
As Botswana have no major dam situated within the Orange River Basin.
4.2
Lesotho
The main flood control structures in Lesotho comprise of Katse Dam and Mohale Dam
which forms part of the Lesotho Highlands Scheme. Both these dams have uncontrolled
spillways and their outlet works have primarily been designed to release environmental
flows. Natural flood attenuation as a result of the size of each reservoir is therefore the
only flood control that would take place during flood events. It should, however, be noted
that the releases from the outlet works of both these dams could cause some localized
flooding in the vicinity of the dam walls especially during "sunny day" releases.
None of the other structures for example Matsoku Weir and Muela Dam is of sufficient size
or has a large enough catchment for significant flood attenuation.
4.3
Namibia
There are seven dams within the Orange River Basin in Namibia. The largest dam
(Hardap Dam) is the only dam with a gated spillway while all the other dams (Oanab Dam,
both Otjivero Dams, Daan Viljoen Dam, Tilda Viljoen Dam and Naute Dam) have
uncontrolled spillways and outlet works that have only been designed to release small
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flows. Natural flood attenuation as a result of the size of these reservoirs with uncontrolled
spillways is therefore the only flood control that would take place during flood events.
It is important to note that the releases from Hardap Dam could cause flooding
downstream of the dam wall especially during "sunny day" releases. Sufficient warning of
such releases is therefore essential.
4.4
South Africa
4.4.1
Vaal River System
The main flood control structures on the main stem of the Vaal River System comprise of
three gated dams namely Grootdraai Dam, Vaal Dam and Bloemhof Dam. There are also
a number of smaller gated structures on the main stem for example Vaal Barrage and
Vaalharts Weir. It is important to note that the releases from these dams/weirs could cause
flooding downstream of the dam walls especially during "sunny day" releases. Sufficient
warning of such releases is therefore essential.
The main flood control structures on various tributaries comprise main dams with
uncontrolled spillways and outlet works that have primarily been designed to make
releases for the various water uses as well as environmental flows. Natural flood
attenuation as a result of the size of each reservoir is therefore the only flood control that
would take place during flood events. These dams include:
· Upper Vaal Sub-system
Saulspoort Dam;
Sterkfontein Dam;
· Middle Vaal Sub-system
Erfenis Dam
Allemanskraal Dam;
Koppies Dam;
Klipdrift Dam;
Boskop Dam
Klerkskraal Dam;
Rietspruit Dam;
· Lower Vaal System
Spitskop Dam;
Taung Dam;
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Wentzel Dam;
4.4.2
Upper Orange River System (excluding Lesotho)
The main flood control structures on the main stem of the Upper Orange River System
comprise of two uncontrolled dams namely Gariep Dam and Vanderkloof Dam. It is,
however, important to note that the both these dams have significant outlet works as well
as hydro-electrical power stations that can make releases that could cause flooding
downstream of the dam walls especially during "sunny day" releases. Such releases have
resulted in the loss of life in recent years. Sufficient warning of such releases is therefore
essential. There are one gated dam (Welbedacht Dam) on the Caledon River. This dam
has, however, silted up to such an extent that its attenuation capacity has greatly reduced
since its completion in the 1960's.
The main flood control structures on various tributaries comprise main dams with
uncontrolled spillways and outlet works that have primarily been designed to make
releases for the various water uses as well as environmental flows. Natural flood
attenuation as a result of the size of each reservoir is therefore the only flood control that
would take place during flood events. These dams include:
· Caledon Sub-system
Knellpoort Dam;
Armenia Dam;
Egmont Dam;
· Modder/Riet Sub-system
Kalkfontein Dam
Tierpoort Dam;
Krugerdrift Dam;
Rustfontein Dam;
4.4.3
Lower Orange River System
The main flood control structures on the main stem of the Lower Orange River System
comprise of a number of smaller structures with uncontrolled spillways for example
Boegoeberg Dam and Neusberg Weir. These structures offer very limited attenuation to
floods on the main stem.
There is only one significant flood control structure on a tributary namely Smart Syndicate
Dam. This dam has an uncontrolled spillway and outlet works that have primarily been
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designed to make releases for irrigation. Natural flood attenuation as a result of the size of
the reservoir is therefore the only flood control that would take place during flood events.
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5
RESERVOIR OPERATING STRATEGIES FOR ALL MAJOR RESERVOIRS
It is important to understand that the majority of dams are operated by both long term
operating strategies as well as short term operating rules for use during flood conditions.
The purpose of the long term operating strategies normally is to ensure the optimum use
of the relevant water resource (these operating rules are discussed in more details under
Task 3 (ORASECOM: 2007)). With regards to the short term operating rules (including
flood routing procedures) that are used during flood conditions, international accepted
practice have it that the routing procedures should satisfy the following in order of
importance:
· The safety of the dam as first priority (the impact of a dam failure would be
catastrophic in terms of possible loss of life, direct and indirect financial, social,
socio-economic and environmental impacts compared to any other impact or
issue); and
· Second priority would be to minimise possible loss of life (maximise public
safety) as well as to minimise other impacts during flood events (for example
direct and indirect financial, social, socio-economic and environmental
impacts) ­ especially during flood events probability of exceedance of more
than 0.5%.
These short term operating rules (including flood routing procedures) are especially
applicable to dams with controlled spillways and/or significant flood outlet works as no
short term operating rule is applicable to dams with uncontrolled spillways and insignificant
outlet works as the operator in this case would no control over the releases from the dam.
5.1
Botswana
As Botswana have no major dam situated within the Orange River Basin there is therefore
no reservoir operating strategies in place.
5.2
Lesotho
There are Operations and Maintenance Manuals as well as Emergency Preparedness
Plans available for both Katse Dam, Mohale Dam as well as Muela Dam.
5.3
Namibia
For Hardap Dam the flood routing procedures were updated in 2007 to satisfy the above-
mentioned international practice as a consequence of the 2006 flood event. A detail "Flood
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Management Strategy" is annually compiled by NamWater and updated on an annual
basis in October/November for the upcoming flood season. The purpose of this manual is
to set down guidelines that facilitate the activities and responsibilities that are critical for
flood releases from Hardap Dam and includes:
· Responsibility for flood control;
· Chain of communication and action; and
· Annual procedures which include updating the telephone contact list, pre-
season activities, activities during the rainy season during both communication
breakdown and normal communication periods (described in more detail in
following section) as well as post-season meetings.
In general operation decisions are made on an hourly basis in the Windhoek offices of
Namwater during flood events using all available information from the existing early
warning and monitoring system together with a spreadsheet-based flood routing
procedure. This decision is then communicated to the operator at the dam. It is also
important to note that the procedures followed compare favourably with similar procedures
used for gated dams in South Africa.
Should communications with the operator breakdown for more than a certain period of
time, the operator will use the short operating rule set out in the "Flood Management
Strategy" to operate the dam.
5.4
South Africa
Short term operating rules for all the gated dams (Vaal Dam, Grootdraai Dam etc.) as well
as dams such as Gariep Dam and Vanderkloof Dam with significant outlet works is
normally compiled by Directorate: National Water Resources Planning Systems of DWAF.
In addition to this Operation and Maintenance Manuals as well as Emergency
Preparedness Plans should be compiled for each dam classified to have a safety risk
according to Dam safety legislation.
The Operation and Maintenance Manuals normally includes the short term operating rules
while the Emergency Preparedness Plans include the following:
· An inundation map of the downstream area; and
· Responsibility, chain of communication and action during emergencies.
In addition to this a Flood Management Center (FMC) is operated by DWAF's national
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Task 5: Flood Management
office. The main functions of the FMC are among other things:
· The continuous, real-time monitoring of rainfall and flows in the Vaal and
Orange Rivers; and
· The management of these river systems in extreme flood situations.
It is important to note that both these rivers are managed as a system and not as individual
dams to minimize flood damage and to maximize storage after the flood situations.
The following information is received by the FMC and is used for flood-related modeling
and flood forecasting:
· Real-time rainfall and flow data; and
· Weather forecasts.
In return the FMC provides:
· Flood warnings to Regional Offices, international neighbours and the public, as
appropriate;
· Flood management decisions for major dams;
· Real-time flow data on the internet; and
· Post-flood calculations and documentation.
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6
EXISTING DISASTER MANAGEMENT STRATEGIES
6.1
Botswana
Following the United Nations International Decade for Natural Disaster Reduction, the
Government established a National Committee on Disaster Preparedness (NCDP) in
1993. However, in 1996, the Government formulated the National Policy on Disaster
Management. The programme dealt with disaster management comprehensively by giving
equal focus to all disaster management elements (prevention/mitigation, preparedness,
response and recovery).
The overall responsibility for disaster management rests with the Office of the President. In
1998, the National Disaster Management Office (NDMO), responsible for overall
coordination of disaster management in the country established. Its major responsibility is
to ensure a high state of disaster preparedness and capacity to deal with any eventuality.
It also has to facilitate integration of disaster management into sectoral polices and
programmes. In addition to this there is also an inter-ministerial National Committee on
Disaster Management, the National Disaster Management Technical Committee which is a
multi-sectoral technical advisory body composed of professionals from all stakeholders
represented in the NCDM and District Disaster Management Committees for each
city/town and District to oversee the implementation of disaster management in districts.
The National disaster relief fund was established in 1996 and is administered by the
NDMO. Its purpose is to provide assistance to natural disaster victims to meet their life
sustaining needs such as shelter, food and provision of sanitary facilities.
Though the Policy and the above structures exist, the country doesnot have other
instruments like a National Disaster Management Plan and relevant legislation in place.
6.2
Lesotho
Lesotho first promulgated its Disaster Management Act in 1997 which was followed by the
development of a National Disaster Management Plan and the Disaster Management Plan
to operationalise the plan. As a consequence the Disaster Management Authority (DMA)
(a department in the Office of the Prime Minister) was established as well as the Board of
Directors and the multi-sectoral working groups at national, district and community/village
levels. Finally, a Disaster Management Fund has been established to which funds are
committed on an annual basis and which is managed by the DMA.
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6.3
Namibia
In Namibia disaster management is the responsibility of the Emergency Management Unit
(EMU) in the Office of the Presidency. A National Disaster Plan has been compiled by the
EMU. The Disaster Plan serves as a guideline for co-ordination of disaster programmes
and activities. It also makes provision for a National Emergency/Disaster Fund managed
by the EMU. The National Flood policy and strategy forms part of the National Disaster
Plan and are the responsibility of the Minsiter of Agriculture, Water and Rural
Development. At lower levels the Regional, Constituency and Village Emergency
Management Units are responsible or co-ordination and management of emergency
activities.
6.4
South Africa
In contrast with Botswana, but similar to Lesotho, South Africa first promulgated its
legislation (Disaster Management Act No 57 of 2002) which was followed by a Disaster
Management Framework that set out the operationalisation of the act. As a consequence
both the Intergovernmental Committee on Disaster Management as well as the National
Disaster Management Advisory Forum (NDMAF) was established. These institutions are
responsible for changes in policy. In addition to this a National Disaster Management
Centre (NDMC) has been established and is functional as well as Provincial and Municipal
Disaster Management Centers. Flood disaster relief funds are administered by DWAF on
behalf of the NDMC.
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7
CONCLUSIONS AND RECOMMENDATIONS
7.1
Conclusions
7.1.1
Areas prone to flooding on a global scale
Sufficient information is available on areas prone to flooding to provide a clear picture for
the purposes of this study. Should one however want to develop a detail flood disaster
management plan more detail information in the form of inundation maps for different
floods sizes for all the main rivers would be required.
7.1.2
Flood forecasting capabilities
Flood forecasting capabilities exist for the whole Orange River Basin. Uncertainty
however, exists on the use of rainfall forecasts in operational decisions. Concern have also
been expressed regarding the lack skilled human resources and financial resources, an
insufficient, diminishing and vandalized monitoring network and the accuracy of the
especially short term rainfall prediction models.
7.1.3
Flood control works
Sufficient information is available on flood control works for the purposes of this study.
7.1.4
Reservoir operating strategies for all major reservoirs
Sufficient information is available on reservoir operating strategies for the purposes of this
study. Should one however want to develop a detail flood disaster management plan more
detail information of the short term reservoir operating strategies for