Water security and climate change assessment

The following is an executive summary of a report by the World Bank on the implications of climate change on water security in Lesotho.

Abundant water, along with high altitude and geographic proximity to major demand centers in southern Africa, is one of Lesotho’s most valuable renewable and sustainable natural assets. In a country characterised by high levels of poverty and income inequality, water contributes roughly 10 percent to overall gross domestic product (GDP). A large portion of this benefit comes from revenues associated with the Lesotho Highlands Water Project (LHWP), a multistage infrastructure project that enables the transfer of water from the water-rich highlands of Lesotho to the economic engine of the African continent in Gauteng and contributes to the development of hydropower resources in Lesotho. Balancing the opportunities afforded by the LHWP with the need to enhance national water resources infrastructure and increase water security against potential future vulnerabilities is central to the government’s long-term vision for development and to sustainable economic growth.

This analysis conducts the first systematic examination of the vulnerabilities of Lesotho’s water management system to climate change by exploring a set of adaptation strategies across a wide range of potential future conditions.

Given the importance of water to long-term sustainable economic growth in Lesotho, extensive quantitative and qualitative analyses have been used to identify strategies that demonstrate successful system performance over a wide range of plausible future scenarios. The analysis looks specifically at the need to ensure continued development of water resources within Lesotho to increase security around the nexus of water, food, and energy along with sustained economic development, while also ensuring that Lesotho is able to meet its obligations under the Treaty with South Africa governing the LHWP.

The analysis does not prescribe a water management strategy for Lesotho based on a single prediction of the future, but quantifies the range of possible future conditions to empower stakeholders and demonstrate the benefits that can be realized over a broad range of possible future outcomes.

Developing a System Model for Lesotho.

The analysis is based on a water resource decision support model developed specifically for Lesotho. The Water Evaluation and Planning (WEAP) model couples climate, hydrologic, and water management systems to facilitate an evaluation of the uncertainties and strategies of impacts on specified management metrics. The WEAP model has been developed over the past 20 years by the Stockholm Environment Institute working in partnership with a number of agencies (including the World Bank) and has been applied in numerous research and consultative projects around the world. The WEAP model is designed to evaluate the performance of water supply reliability for different water use sectors (such as domestic and industrial water users, rainfed and irrigated agriculture, hydropower, instream flow requirements, and water transfers to South Africa) across a range of future climate conditions. The model lays a foundation for a national system to monitor the development and use of water resources in Lesotho. The Lesotho WEAP model was developed through an iterative series of workshops with key stakeholders from various governmental departments.

The first step in the development process focused on developing the rainfall and runoff routines and calibrating these to observed historical streamflow time series. The second step focused on adding representations of the existing and planned water management infrastructure to the model to facilitate scenario planning.

Assessing Climate Change Scenarios for Lesotho.

The WEAP model was used to simulate the historic climate based on data from the national government archives and global datasets available in the public domain. These included 121 downscaled Global Climate Model (GCM) projections of future climate over two possible water demand scenarios, for a total of 244 scenarios up to the year 2050. This large collection of future climate projections is based on a bias-correction and spatial downscaling (BCSD) procedure that applies a four-step process to generate monthly climate on a 0.5° grid for the world’s landmasses. The grid cells corresponding to the river basins of Lesotho are extracted, and an averaging procedure estimates average monthly precipitation and temperature for each catchment in the WEAP model.

Robust Decision Making.

Although WEAP is a powerful modeling tool, models applied in isolation do not necessarily provide guidance to support decision making and policy setting. To play this role, models must be embedded within decision analytic frameworks that guide the development of experimental designs and the evaluation of the results that the models produce.

In this study, a robust decision-making (RDM) framework was applied to frame the analysis and help interpret the results. The analysis examines which strategies demonstrate robust performance across the range of future scenarios to show positive performance over a broad range of circumstances.

Because individual future scenarios cannot be assigned a probability of occurrence, the use of broadly applicable robust strategies reframes the management dilemma for climate adaptation.

Demonstrations of robustness can empower decision makers to implement interventions even under highly uncertain conditions.

The project worked with national experts, stakeholders, and policy makers in an iterative process to identify key uncertainties that could compromise

Lesotho’s water management strategy. These include climate change, domestic and industrial water demand, agricultural production, and changes in water transfer opportunities. The stakeholder process was also used to identify a range of potential adaptation strategies. These included new infrastructure, such as the Lowlands Bulk Water Supply Scheme, which could provide additional water to communities across the lowlands of Lesotho, the allocation of water for further development of irrigated agriculture, and development of future phases of the LHWP. To evaluate the performance of these strategies, stakeholders specified the key management metrics of the water supply system, including the reliability of water for agriculture, domestic and industrial demands for Lesotho, as well as water transfers.

Capacity Building.

Recognizing that adapting to future challenges, including climate change, is a long-term process, the approach to model development and application of the analytical tools focused on capacity enhancement for resource managers. The aim was to provide the necessary background and experience needed to use the models and analytical tools in support of forward-looking decision-making processes. A number of training sessions were held with managers and professionals to (1) improve the development and use of the WEAP-based water management model; (2) understand and apply the statistical programming language, R, for climate data analysis; and (3) apply the interactive visualization software, Tableau. Proficiency in WEAP will allow planners to continue to use, improve, and interrogate the WEAP model, while the R language is crucial for climate analyses and GCM processing for future climate investigations. The Tableau software facilitates the interpretation of large quantities of results that often characterize climate change investigations. Opportunities remain in Lesotho for further capacity building in these tools to examine and evaluate climate projects for use in the WEAP model. This experience in Lesotho suggests also that similar capacity building efforts could be extended to other countries and water management authorities within the Southern African Development Community as a means of supporting vulnerability assessment and adaptation planning.

Climate Change Projections.

Key vulnerabilities within the current system have been identified with respect to water supply for domestic and industrial water demand, irrigation, and water transfers. A summary of projected future surface air temperatures from the ensemble of GCM datasets analyzed for this study suggests warmer conditions for the period from 2030 through 2050. The projected increase in air temperature derived from the GCMs ranges from a low of about 0.8°C to a high of 2.9°C above the historical average of 12.7°C. In contrast, there was no strong consensus among the climate models for projections of future precipitation for the same period.

Some GCM-modeled future projections, on average, are wetter while others are drier. For the twenty-year period, more future projections are drier (64 GCM projections) on average than wetter (57 GCM projections). The range of projected future precipitation includes both an increase and decrease of about 20 percent or 160 mm annually. The historical annual average precipitation over Lesotho is about 760 mm. These climate projections for precipitation and temperature are shown in figure ES.1.

Climate change scenarios suggest diminishing capacity to meet the future growth in demand for domestic and industrial water in Lesotho. Over half of the future scenarios evaluated predict unmet domestic demand of more than 20 percent for the 2041–50 period. The analysis shows that development of the Lesotho Lowlands Water Supply Scheme (LLWSS) would reduce the vulnerability to unmet demand and improve overall water security for the continued economic development of the industrial sector, meet increasing domestic demand, and provide for further development of irrigation potential. The Metolong Dam and Water Supply Program, the first project to be implemented under LLWSS, has increased security of supply to Maseru, Teyateyanang, Roma, Morija, and other surrounding towns. The study recommends the implementation of further phases of LLWSS as an adaptive measure to mitigate the potential effects of future climate change and current variability.

Lesotho’s agricultural sector is predominantly rainfed, thus susceptible to climatic variations and vulnerable to projected increases in climate variability.

Rising temperatures will increase the amount of water required for crops, exacerbating water stress during dry periods. Without irrigation schemes, any shift toward drier precipitation patterns could reduce agricultural yields. Coupled with projected increases in population, Lesotho’s dependence on food imports will likely increase. Developing additional irrigation capacity and expanding existing schemes could increase food security. The increased allocation of water required to expand from the 1,000 hectares currently under irrigation to the 12,000 hectares that have been identified as potentially irrigable could be met without reducing transfers of water to South Africa under all future scenarios.

Water transfers to South Africa will be increasingly vulnerable in the coming decades (see figure ES.2). Specifically, the analysis finds that in 10 percent of the climate scenarios (indicated as the points outside the shaded area in figure ES.2) the average amount of unmet water transfers increases from about 500 million m3 in the 2016–20 period to almost 2 billion m3 in the 2046–50 period in the absence of implementation of the additional phases envisaged. Delays in implementing the LHWP could undermine water security in South Africa and limit the economic and development benefits that accrue to Lesotho. The analysis then finds that various adaptation strategies, including full construction of the proposed Polihali Dam and the full buildout of all five phases of the LHWP infrastructure, both increase the amount of transfers to South Africa and increase their reliability over a wider range of climatic conditions (see figure ES.3). For each of the strategies evaluated, the analysis identifies the key climate conditions for which the deliveries to

South Africa (and other performance metrics) are unacceptable. For example, the analysis confirmed that the system with the Polihali dam is highly reliable under most climate futures and that deficits occur only in the very driest of futures (16 of the 122 cases, in which precipitation is less than 725 millimeters per year).

The development of the water transfer and hydropower components under Phase 2 of the LHWP are projected to bring additional benefits to Lesotho.

In addition to increasing the potential delivery of water in response to growing demand in South Africa, the projects are expected to contribute about

11,000 jobs annually during the construction period. Approximately half of these jobs will be in construction, with the rest in such indirect activities as agriculture, transport, and services. The majority of these jobs will be temporary and so the challenge will be to transfer skills and leverage income for sustainable employment after major civil works are completed.

However, improved road access and reduced travel times and transport costs will have substantial longer-term benefits through better access to and from agricultural markets and will boost tourism and other local development opportunities.

Implementing the lowlands scheme and expanding irrigation through the diversion of a portion of water captured by the LHWP would not jeopardize the reliability of the water transfers to South Africa. The analysis identified both a Plus Polihali, Lowlands, and Irrigation strategy and a Plus All Highlands,

Lowlands, and Irrigation strategy. These two strategies both dramatically increase the amount of water exported to South Africa and divert enough water to the lowlands to significantly reduce the projected shortages and increase food production in future decades (see figure ES.4).

The assessment indicates that transfers to both South Africa and Botswana could be reliably met under future scenarios in which the climate is about the same, or wetter, than as shown by historical trends. Under drier climates, there would be a tradeoff between meeting the transfer targets for Botswana and South Africa. The percentage impact on the transfers to South Africa would be much lower than that on the transfers to Botswana. When the transfers to Botswana are prioritized, they are very reliable, with shortfalls in only

4 of the 122 climates examined. With the development of the Polihali Dam, the South African transfer targets can be met under most, but not all, plausible future climates.

Conclusions and Recommended Next Steps.

The analysis outlines a range of possible scenarios for Lesotho based on a comprehensive assessment of the potential changes associated with climate change from 2030–50. The analysis does not prescribe a water management strategy for Lesotho based on a single prediction of the future, but quantifies the range of possible future conditions as characterized by the latest GCM results and stakeholder assessments of internal demand predictions and future water transfers. This quantification empowers stakeholders to act with more confidence by demonstrating that the implementation strategies can provide benefits to water resources management and provision over a broad range of scenarios.

Implementing a series of the adaptive interventions identified can improve overall system performance across the range of future scenarios and enhance the overall water security for Lesotho. Specifically the analysis draws the following conclusions:

• Climate change will create important determinants for the future, long-term sustainable macroeconomic development of Lesotho. All future scenarios consistently demonstrate an increase in temperature, while changes in patterns of precipitation vary among the different scenarios. This will have implications for long-term domestic and industrial water security, patterns of agricultural production, and opportunities afforded through the further development of water transfer infrastructure.
• • Domestic and industrial water security is highly vulnerable under historical and current climate conditions, as well as under the full range of climate future scenarios. These results are driven by the current configuration of the water management infrastructure system, which does not provide interconnections between the developed water sources used to support the LHWP with domestic and industrial demand in the lowlands.
• Agriculture production will remain vulnerable to inter-annual variability over the coming decades, particularly with continued reliance on rainfed agriculture. Irrigation schemes can be supported without significant reductions in transfer reliability to South Africa. Investing in monitoring and enhanced data acquisition would help improve future adaptive capacity and on-farm responses to changes in climate patterns and levels of variability.
• The LHWP will continue to reliably meet transfers to South Africa over the coming decades unless climate conditions are about 5 percent drier or more than the historical record. Construction of the Polihali Dam, and associated infrastructure, will increase transfers and reliability. Build-out of the full LHWP increases the transfer capacity and can also support the development of water supply schemes in the lowlands along with irrigation development. Adapting to future challenges, including climate change, is a long-term process that affords time and opportunity for strategically positioned and driven enhancements. The analysis clearly points to a number of areas for further development.

Improve Data Monitoring and Management.

Data limitations will undermine Lesotho’s ability to monitor predictions and respond to changes in climate.

Design and implementation of an optimized hydrometeorological network would enhance the capacity of Lesotho to prepare for and respond to potential future changes in climate. Detailed agricultural data and information about the economic uses and value of water were not readily available.

These limitations led to a more cursory evaluation of the agricultural sector and the omission of a more formal economic analysis.

Continued Capacity Enhancement.

The tools and analysis required to support the planning for robust climate adaptation necessitate sustained capacity development. The nature of the analysis here provided support to the first iteration of an interactive participatory process. The time required to develop the tools and capacity needed provides a foundation, but should be further developed and integrated into government planning processes.

Economic Evaluation.

The climate modeling and RDM framework illustrates important decision pathways for future development in Lesotho. The cost and valuation data required to support a cost-benefit analysis across the wide range of climate conditions would also support an important economic evaluation of different adaptation options. These data could be incorporated into the current RDM analysis to evaluate the economic robustness of the different adaptations.

Extending Adaptation Analysis.

Using the existing data and tools to undertake additional iterations of the vulnerability and adaptation analysis up to the end of the 21st century would increase the scientific rigor. The analysis would enhance the capacity to evaluate climate risks and weigh different tradeoffs. Further adaptation of the WEAP model to a shorter time step, such as one day, would enable the evaluation of operational strategies for water allocation among competing uses, such as water deliveries and timing for domestic and agricultural use, as well as hydropower generation. Extending the geographic scope of the model to demand areas in South Africa that rely on water imported from Lesotho would also produce a more complete understanding of vulnerabilities and tradeoffs.

Lowlands Water Supply Scheme.

Continued development of the LLWSS is critical to improving the reliability and resilience of the domestic and industrial sectors. Exploring interconnections between the developed water resources through LHWP and linking these to address domestic and industrial demands in the lowlands could help improve the resilience of the existing system. Such integrated planning could also help to manage the associated political economy between perceived national benefits and the development of water transfer projects.

Agricultural Sector Assessment.

The results highlight the need for a more thorough assessment of the risks and opportunities for Lesotho’s agricultural sector of potential changes in climate. An evaluation of the implications of increasing atmospheric carbon dioxide (CO2) concentrations, together with rising temperatures and water stress on agricultural productivity, should be further elaborated. A better understanding of these dynamics could help develop agricultural strategies suited for the unique climatic changes underway in Lesotho. This information could help direct a program to incorporate the traits of such plans into desirable crop production cultivars to improve yield.

Using a deliberate, inclusive process with Lesotho managers, this project incorporated Lesotho’s most pressing needs to demonstrate the vulnerabilities, challenges, and opportunities in the Lesotho water management system.

With a new quantification of options for improving system robustness, managers can move forward with plans that are most aptly positioned to support their objectives.