Lesotho is considered the water tower of Southern Africa underscoring its relevance for not only its own but also the region's water supply. Domestically, the Metolong Dam system supplies water to more than two thirds of Lesotho’s population and water intensive economic sectors in the urban catchment of Maseru. At the same time, the Metolong Dam system is exposed to a series of natural and anthropogenic hazards, as well as various cascading impacts, which are compounded by climate change and have the potential to compromise the service provision in the longer term. The analysis of climate projection models for the Metolong Dam system predicts for the 2050s-2080s increasing hot temperature extremes, drought severity, and wildfires, as well as increasing frequency and intensity of storms and heavy precipitation events. In view of climate change being a key driver of risks, it is critical to systemically integrate existing and emerging risks into the planning and management of water infrastructure supply systems.
Climate Risk Assessment of the Metolong Dam System
Against this backdrop, the Government of Lesotho, in cooperation with the Global Initiative on Disaster Risk Management (GIDRM) has engaged, under the umbrella of the National Integrated Catchment Management Program (RENOKA), in the process to assess the prevailing and future climate risks of the Metolong Dam infrastructure system, and its relevant up and downstream components, including its reservoir and catchment, as well as water treatment plant and its water distribution system.
This is being achieved through the application of the Public Infrastructure Engineering Vulnerability Committee (PIEVC) Protocol in partnership with the Climate Risk Institute (CRI). Applying the PIEVC in Lesotho aims to provide a better understanding of the service reliability of the dam system under changing climate conditions and identify potential consequences of varying water service levels for key user groups. The assessment forms the basis to evaluate implications for sustainable water provision (thereby, a contribution to sustainable development) in the catchment and the water sector from a risk-informed development perspective. It thus provides a critical tool to support decision-making and risk-informed planning and implementation processes.
Following an inception workshop and online training on the use of the PIEVC methodology during August to October 2022 the risk assessment of the Metolong Dam system was primarily carried out during a four-day workshop from January 31 to February 3, 2023. As a multi-faceted and participatory process, allowing transparency, co-ownership and collective accountability among stakeholders, the assessment brought together over 50 practitioners, managers, and decision-makers from different sectors (e.g., public infrastructure & service provision; natural resources, water & land management; climate & meteorology; disaster risk management; forestry; agriculture; industry; academia; and local communities).
PIEVC Assessment & Preliminary Findings
The assessment workshop was kick-started with a guided tour of the Metolong Dam and Water Treatment Plant. The on-site visit offered additional insights into some of the risk drivers and impacts upstream highlighting the interconnection of the three scales of assessment (i.e., watershed and reservoir, dam infrastructure, and downstream user groups).
The workshop’s methodological approach and stakeholder-driven assessment was structured along three core steps:
- Impact chain assessment: Impact chains provided a suitable entry point to understand the context, drivers of systemic risks, and their cascading impacts across the three assessment scales of the Metolong Dam system. Discussions and validation allowed to unpack how climate change, extreme events and bio-physical impacts on the environment interact with key grey and green infrastructure components of the system as well as with socio-economic, structural, and environmental development pathways at large.
- Risk-screening for each component of the assessment scale: Having laid the foundation for a risk screening, the exposure of key infrastructure components was evaluated and then followed by a scoring of potential severity of impact. Each interaction namely, the respective exposure, severity of impact (vulnerability), and climate likelihood of occurrence (hazard) was multiplied in order to receive a risk score.
- In-depth assessment of selected key impacts: Key impacts like the lifecycle reduction of the dam reservoir were assessed more in-depth and complemented by discussions on risk tolerances and recommendations towards potential options to address and adapt to the identified risks.
Preliminary findings from the risk screening include i.a.:
- Occurrence of heavy precipitation scenarios posing “significant” to “major” risk to watershed components included risks to rangeland, agricultural lands, wetlands, forest, and transportation networks.
- Increase of heavy precipitation scenarios was identified as posing a “major risk” to erodible soils in the watershed and reservoir.
- Heat waves and different heavy precipitation scenarios put the functioning of the water treatment works at “significant” risk.
- Increased occurrence of 100-year flood events creates significant risk to various components of the dam infrastructure, specifically drainage and access galleries, outlet works, ICT, and supporting infrastructure.
- Pumping stations, transmission and distribution mains as well as water demand are expected to face “moderate” to “significant” risk during heatwaves and heavy precipitation scenarios.
- Heat waves and different heavy precipitation scenarios put people’s and worker’s health and safety at “high” risk across all scales.
Finally, preliminary findings of the risk screening and recommendations were presented to decision-makers from different institutions, sparking discussions on related adaptation options and risk-informed development pathways. In this respect, assessment findings directly inform ReNOKA’s risk-informed integrated catchment management approach, which at the same time also serves as a vehicle to address risk drivers related to land and water management practices identified in the assessment. Decision-makers also emphasized the importance of addressing risks in a systemic, proactive, continuous, cross-sectoral and inter-institutional manner, signaling their commitment to working collectively towards ensuring water service reliability and resiliency of the system.
The assessment process has also laid the foundation for the institutionalization of risk assessments in the planning and management of critical infrastructure systems in Lesotho at large. Encouraging all national, subnational, state and non-state actors, Mr. Lebohang Maseru (Lesotho’s Acting Commissioner of Water) highlighted to:
“seize this opportunity to place climate risk assessment as a key priority in infrastructure planning and enable Lesotho to champion the process as a good practice in the region.”
The learning experiences from Lesotho and the climate vulnerability assessment will be upscaled to the Orange-Senqu River Commission (ORASECOM) and the SADC Technical Working Group on Disaster Risk Reduction. This interface between the national and regional level will contribute to the use of the risk-informed development guiding principles, tools, and methods to strengthen the resilience of existing infrastructure and future investments for SADC’s regional integration.
Disclaimer: The process is supported by the Global Initiative on Disaster Risk Management (GIDRM) commissioned by the German Federal Ministry for Economic Cooperation and Development (BMZ) and implemented by the Deutsche Gesellschaft für internationale Zusammenarbeit (GIZ). The PIEVC risk assessment is being carried out in partnership with the Climate Risk Institute (CRI). PIEVC is hosted and promoted by an alliance of GIZ, CRI and the Institute for Catastrophic Risk Reduction (ICLR).