Overview of the Lesotho Highlands Water Project (LHWP)
The Lesotho Highlands Water Project, The Beginning
Senqu/Orange river rises in the mountain region of Lesotho, traversing in a generally western direction nearly 2000km to the Atlantic Ocean and being joined half way by the Vaal river coming in from the north-east.
Although the mountain region of Lesotho constitutes only 5% of the the total catchment of the Senqu/Orange river, it provides about 50% of the total catchment run-off.
The water originating in the mountains is characterised by good chemical quality and low sediment content.
The topography of the region allows for the possibility of developing a hydro-power generation in Lesotho in conjunction with the the provision of water supplies to the RSA.
The Lesotho Highlands Water Project (LHWP) was identified more than 50 years ago as the least cost effective water resource exploitation to benefit both the peoples of the Kingdom of Lesotho (Lesotho) and the Republic of South Africa (RSA).
The Objectives of the Project are :
i) To provide revenue to Lesotho by transferring water from the catchment of the Senqu/Orange river in Lesotho to meet the growing demand for water in the RSA's major industrial and population centres
ii) To generate hydro-electric power for Lesotho in conjunction with the water water transfer
iii) To promote the general development of the remote and underdeveloped mountain regions of Lesotho, while ensuring that of Lesotho, while ensuring that comprehensive are taken to counteract any adverse effects which the Project might have on the local population and their environment
iv) To provide the opportunity to undertake ancillary developments such as the the provision of water for irrigation and potable water supply
The Climate of Lesotho
Lesotho lies within the summer rainfall area of Southern Africa and more than 85% of the annual rainfall occurs in the seven months from October to April. Mean annual rainfall ranges from less than 600mm in the lower Senqu valley to 1000mm along the mountain ranges.
Interannual variations in rainfall are significant with prolonged dry or wet periods occuring. At higher altitudes, witer nights are very cold and even in the low-lands, frost occurs on over 80 days of the year. In the mountains areas with elevations exceeding 3000m, frost can occur on over 250 days in the year.
Lesotho's Water Resources
Water is a resource that Lesotho has in relative abundance. Lesotho's water resources far exceeds its possible future requirements, even allowing for possible future irrigation projects and for general development and improvement of living standards.
The average total available water in Lesotho is about 150m3/s and current national consumption is not more that 2m3/s.
Estimates of the natural mean annual run-off at the sites of the main project. (Feasibility study estimates).
Geological make- up in the LHWP
The overall geological structure in the LHWP area consists of layers of nearly horizontal sedimentary rocks of the RSA Karoo sequence, capped by basalt flows and intruded by dolerite dykes and sills. The geology has an important influence on tunnelling operations, foundation conditions and availability of construction materials.
Basaltic conditions the underlying sandstone of the Clarens will provide favourable tunnelling conditions.
Poorer tunnelling may occur in the vicinity of the dykes where some minor seepage is expected. In the lower formations of the Karoo sequence, weaker sedimentary rocks occurt and tunnelling conditions are more variable.
Groundwater inflow is not likely to be significant, except locally at dykes, but some siltstones and claystones tend to disintegrate rapidly with changes in moisture content and have realatively low strength.
The LHWP's dams are founded on either the basalt ( Katse, Mohale, Matsoku) or the underlying competent sandstone ('Muela and future phase dams). Foundation conditions are good at all sites with adequate strength, low permeability and limited jointing.
Dolerite from dykes and dense doleritic basalt can be crushed to produce coarse and fine concrete. This was actually done in the construction of Katse and Mohale dams. Natural sources of sand and gravel are limited in the higher regions of the Phase I but will become significant in lower reaches of Senqu river for further phases.
The project is located in area of low tectonic activity and low seismic risk. Only one significant incidence of seisimic activity occurrred in 1996? during the filling up of Katse dam at a place called Mapeleng.
The activity caused damage to houses tearing them apart and causing panic in the area. The affected households were received replacement housing of superior quality and standard as compensation from the incidence. No further seismic occurrence has happened since.
WHO's WHO IN THE CONSTRUCTION OF PHASE I OF THE LESOTHO HIGHLANDS WATER PROJECT
Phase I A
(Katse dam, 45 km Transfer Tunnel, 'Muela Hydrpower Station and Tail Pond, 15 km Delivery Tunnel -south and 22km Delivery Tunnel -north)
Lesotho Highlands Consultants (LHC)- Katse Dam and 45km Transfer Tunnel
A consortium of HWDC (South Africa)
Ninham Shand, WLPU, Keeve Steyn, MJ Mountain, SRK and VKE and
SCBG ( Europe)- SOGREAH (France), Coyne &Bellier (France) Sir Alexandra Gibb & Partners
Supervised the Highlands Water Venture Contractors at Katse Dam. Venture comprised
Impregilo (Italy), Kier (UK), Bouygues (France), Concor (South Africa), Hochtief (Germany) Group 5 ( South Africa and Stirling ( Uk).
Lahmeyer MacDonald Consortium (LMC) - 'Muela Hydropower station and the Tailpond dam
Lahmeyer ( Germany) and Mott MacDonald of the United Kingdom
Supervised The Lesotho Highlands Project Contractors ( LHPC) - 45 km transfer tunnel & 15 km delivery tunnel south
LHPC comprised Spie Batignolle (France), Balfour Beatty (UK) LTA (SouthAfrica) Campenon Bernard (France and Ed Zublin(Germany) and
Electrical and Mechanical subcontracted to the LHPC were:
Neyrpic of France and SDEM of South Africa; Deutsche Babcock of RSA for steel liners for the under river-crossing; Krohne Altometer of the Netherlands for the Flow metres in the delivery tunnel south
Lesotho Highlands Partnership (LHTP - 15km Delivery Tunnel- south
LMJoint Venture- Lahmeyer ( Germany), Mott MacDonald ( UK) and HDTC ( South Africa) - Ninham Shand, VKE, Keeve Steyn, SRK
Highlands Delivery Tunnel Consultants (HDTC)- 22 km Delivery tunnel north - Ninham Shand, VKE, Keeve Steyn and SRK
Supervised the "Muela Hydropower Project Contractors (MHPC) for 'Muela Power station and dam - Spie Batignolle (France), Balfour Beatty ( UK) Campenon Bernard ( France) and Ed Zublin ( Germany). They in turn subcontracted the following for 'Muela Power Station Equipment : Kvaener Boving UK/ABB) generation (Sweden) for the Turbine Generators; ABB Calor Emag Schaltanlagen of Germany for the Transformers; Norelec of France for the substation and Transmission lines.
Mohale Dam, 145m high, concrete face rock-fill embankment- Mohale Consultants Group(MCG) comprising SMEC( Snowy Mountains Engineering Corp of Australia, BKS Inc, Melis & Du Plessis and Stewart Scott of South Africa, Harza Engineering of the USA and Nippon Koei Co of Japan.
MCG supervised Mohale Dam Contractors, a joint venture of Impregilo of Italy, the lead contractor, with Hochtief of Germany and Concor of South Africa. Concor Engineering and ATB join venture were sub contracted to undertake Mechanical and Engineering activities.
Contract Award : 17 March, 1998
Mohale Interconnecting Tunnel to Katse, 32 km long,- The Lesotho Highlands Tunnel Partnership (LHTP) Mohale were the design and supervising consultants. The Team comprised Lahmeyer(Germany), Mott Macdonald (UK) with Consult 4 of South Africa comprising : Ninham Shand, VKE (Van Niekerk Klyn and Edwards), Keeve Stryn ans SRk ( Steffen Robertson and Kirsten) and Knight Piesold
The Contractors comprised a joint venture of Hochtief(germany) contract leader Impregilo (Italy) and Concor (South Africa). Concor Engineering were sub-contracted to the M&E activities.
Contract Award : 18 December, 1998
Matsoku Weir and Tunnel- The design and supervision consultants are Matsoku Diversion Partnership whose composition is Consult 4 (South Africa) comprising Ninham Shand, VKE Engineers, SRK Consulting and Knight Piesold in a joint venture with the Lescon /FMA of Lesotho.
The Construction team, Matsoku Civil Contractors (MCC) comprised a joint venture of Concor (South Africa), Hotchtief (Germany) contrac leader and Impregilo (Italy). Concor Engineering of South Africa and B&W Electrical were awarded sub-contracts in Mechanical and Engineering fields respectively.
Contract Award : 18 December, 1997
Mohale Access roads- GIBB (Lesotho)/BS Bergman (RSA) were the design and supervising engineers. the Contractors were the LTA/Group 5 Joint venture
A TUNNELLIN EXPERIENCE IN THE HEART OF THE KINGDOM OF LESOTHO.
Excavation of the tunnelling required on Phase IA of the Lesotho Highlands Water Project (LHWP) has been an enormous undertaking. Hereunder is a study of the vital statistics that illustrates the scope of the achievements.