Knowledge Framework
Use Cases
- Transfer water between regions — Move large volumes of water from a water-rich region to a water-scarce one through canals, tunnel...
Decision Patterns
- Inter-basin transfer systems — Move water between regions
Overview
The Orange River Transfer Scheme encompasses a series of inter-basin water transfer projects that redistribute water from the Orange-Senqu River system to South Africa’s most water-stressed and economically important region: Gauteng province (home to Johannesburg and Pretoria, with 16 million people).
The centrepiece is the Lesotho Highlands Water Project (LHWP), a bilateral treaty-based project between South Africa and Lesotho. The LHWP captures water in the highlands of Lesotho — where rainfall is high — and transfers it via tunnels to the Vaal River system in South Africa, which supplies Gauteng.
Phase I of the LHWP (completed 2003) includes the Katse Dam (185 m high) and Mohale Dam (145 m high), connected by a 32 km transfer tunnel. Phase II, currently under construction, will add the Polihali Dam and a 38 km transfer tunnel to further augment supply.
Timeline & Location
1966: Orange-Fish Tunnel completed (82 km, one of the world’s longest water transfer tunnels). 1986: Treaty signed between South Africa and Lesotho for LHWP. 1998: Katse Dam completed (Phase I). 2003: Mohale Dam completed and Phase I fully operational. 2014: Phase II treaty signed. 2019: Phase II construction begins (Polihali Dam). 2028 (projected): Phase II completion.
Stakeholders
The Trans-Caledon Tunnel Authority (TCTA) manages the South African side of the LHWP and related transfers. The Lesotho Highlands Development Authority (LHDA) manages the Lesotho-side infrastructure. The project operates under a bilateral treaty between the two governments.
South Africa pays Lesotho royalties for the water transferred, providing a significant revenue stream for Lesotho (approximately 5% of GDP). Rand Water distributes the transferred water to Gauteng municipalities. The Department of Water and Sanitation (DWS) oversees national water resource planning.
Digitalisation & Data
The LHWP uses SCADA systems for dam operations, tunnel flow control, and water level monitoring. Hydrological monitoring networks across the Lesotho Highlands track rainfall, river flows, and dam inflows. The system integrates with South Africa’s Vaal River system operations centre for coordinated water management.
Hazards
Exogenous Hazards
Climate change affecting rainfall patterns in the Lesotho Highlands catchment. Regional political instability. Drought conditions reducing available water for transfer whilst demand grows.
Endogenous Hazards
Dam sedimentation reducing storage capacity over time. Infrastructure ageing across the 60-year-old Orange-Fish Tunnel. High capital costs of Phase II construction. Environmental and social impacts of dam construction on communities in Lesotho.
Cost & Benefit
Cost: LHWP Phase I cost approximately $4 billion. Phase II is estimated at $3–4 billion. The Orange-Fish Tunnel and related schemes represent additional billions in historical investment.
Key Benefits: Provides the water backbone for South Africa’s economic heartland (Gauteng contributes ~33% of national GDP). Generates hydroelectric power for Lesotho. Provides Lesotho with a significant revenue stream through water royalties. Enables food production in the Free State through the Orange-Fish Tunnel.
Resilience Principles Assessment
Assessment of meeting Principles of Resilient Infrastructure
Shared Responsibility (P5)
The LHWP is a model of transboundary water cooperation, with a treaty-based framework that shares benefits between South Africa (water) and Lesotho (revenue and hydropower). The governance structure includes joint oversight institutions.
Proactively Protected (P2)
Phase II construction is underway proactively to augment supply before the gap between demand and available resources becomes critical. The multi-dam, multi-tunnel system provides redundancy.
Socially Engaged (P4)
The LHWP has faced scrutiny over the resettlement and compensation of communities displaced by dam construction in Lesotho. Phase II includes improved social impact mitigation and community development programmes based on lessons from Phase I.
Environmentally Integrated (P3) To Do
Details pending.
Continuously Learning (P1) To Do
Details pending.
Adaptively Transforming (P6) To Do
Details pending.
Futures
Phase II (Polihali Dam) completion is targeted for 2028. South Africa’s National Water Resource Strategy identifies additional augmentation schemes for the Vaal system. Climate change adaptation and demand management are increasingly recognised as necessary complements to supply-side infrastructure.