Secured Urban Water Supply for the City of Windhoek, Namibia
by Johannes Münch (German Federal Institute for Geosciences and Natural Resources)
Key Messages
Water resilience is crucial for Namibia's economic resilience, particularly to ensure food security, as the country is highly vulnerable to water-related risks like droughts and floods.
Closure of the industries in Namibia’s capital of Windhoek due to water scarcity would create dramatic economic losses of about US$ 1.5 million per day on top of remarkable social consequences such as unemployment, poverty, and hunger.
The Managed Aquifer Recharge (MAR) system in Windhoek has proven to be a cost-effective and dependable approach for augmenting water supply, meeting increasing demand, and mitigating the risks of water scarcity caused by droughts and climate change. MAR has increased crop yields by up to 50% in some areas of Namibia and enabled farmers to irrigate larger areas and diversify their crops, resulting in increased food security and income.
In order to ensure the most effective use of resources, investment in water infrastructure must be tailored to meet the specific needs of the country. Conducting a cost-benefit analysis and pilot testing before scaling investments are critical for success, as they enable the accurate measurement of results and performance, providing access to crucial insights.
Namibia’s Economy and Water Risk
Climate resilience is a crucial factor in ensuring economic resilience, particularly in the case of Namibia, a middle-income country located in southern Africa. The country is highly vulnerable to the effects of climate change, and water is at the forefront of its climate resilience efforts. With a population of 2.5 million, Namibia faces the challenges of increasingly frequent and severe droughts and changes in precipitation patterns. These challenges significantly impact the availability of water, agriculture, tourism, and other sectors that are crucial to the country's development. It is, therefore, imperative to address these issues urgently to ensure Namibia's sustainable development from both economic and social perspectives.
In 2022, Namibia's GDP was approximately US$ 23 billion, which translates to a per capita GDP of around US$ 9,200 per year (World Economics, 2023). The Namibian economy is heavily reliant on natural resources, particularly minerals and fish, which account for the majority of the country's exports. The tourism, mining, and agricultural sectors are the main contributors to Namibia's GDP, accounting for approximately 15%, 10%, and 4%, respectively (International Trade Administration, 2023).
Namibia is one of the most water-scarce countries in the world and highly vulnerable to droughts which have led to significant food insecurity with severe social and economic consequences. While agriculture plays a vital role in Namibia's economy, employing more than 50% of the labor force as compared to nearly 20% in tourism and only 3% in mining, the scarcity of water directly limits agricultural productivity, aggravating the issue of food and social insecurity (World Atlas, 2023).
Building economic resilience is imperative for Namibia, particularly in terms of ensuring food security, given the country's susceptibility to water-related risks such as droughts and floods. Namibia has been severely impacted by these challenges, As of October-November 2021, approximately 659,000 people, or a quarter of Namibia's population, faced crisis levels or higher of food insecurity, with 102,000 people in emergency conditions. This nationwide food insecurity was caused by a drought experienced in 2019, increased prices of food and non-food items between April-September 2021, and the impact of COVID-19 measures on supply chains and livelihoods (IPC, 2021).
It is important to recognize that water scarcity not only exacerbates food insecurity but also other social issues related to health, education, and gender equality. Women and girls, who are often the primary water collectors in rural areas, can be disproportionately affected by the time and effort required for water collection, limiting their access to education and economic opportunities (UNDP, 2022).
Namibia's water supply is greatly affected by the impacts of climate change on the country's limited freshwater resources and high variability in rainfall. The average annual rainfall in Namibia is currently only 350 mm, which has resulted in the country relying heavily on underground aquifers and the perennial river system for its water supply; however, these groundwater resources are facing significant pressure due to over-abstraction, climate change, and land-use practices.
The groundwater resources available in Namibia remain stagnant and are not expected to increase in availability. At the same time, there is an exponential increase in water demand in many economic sectors. This highlights the troubling pattern of rising water demand surpassing the supply in the country, despite the current installed capacity of water. Namibia's estimated total renewable freshwater resources are a meager 422.5 MCM per year, and at current rates of demand, they are projected to be overexploited in less than 10 years. This situation underscores the urgent need for Namibia to implement measures to manage its water resources sustainably and efficiently to avoid exacerbating the already critical water scarcity situation.
Managed Aquifer Recharge (MAR) as a Climate Adaptation Measure
Heavy rain and flood events as well as droughts threaten the livelihoods of the people either by a lack of water or by a surplus of water. In these situations, the storage of water in natural or built infrastructure is a key adaptation strategy. Aquifers are nature-based water reservoirs, whose functions can be artificially “enhanced” by MAR. MAR describes the intentional recharge of water to aquifers for subsequent recovery or environmental benefit. Thereby, it takes advantage of surplus water resources during flood periods through storage in the subsurface and its usage during dry seasons. In aquifers, water is well protected against pollution and evaporation, which is an important factor in arid and semi-arid environments and in comparison, with surface water reservoirs.
MAR could be very different technologies, based on infiltration, injection or dam structures. Aquifer Storage Recovery (ASR) and Aquifer Storage Transfer and Recovery (ASTR) are technologies which utilize injection wells to inject water into the aquifer. Other technologies, such as dune infiltration, infiltration ponds, percolation ponds, or rainwater harvesting, accumulate water on the surface and enhance the infiltration into the underground through longer retention times and an increased infiltration area. Other technologies require a greater effort including the construction of underground measures (e.g., underground dams or sand dams). These approaches create artificial underground water storages that have similar properties as natural aquifers. Rainwater, storm water runoff, river water, surface water, or even treated wastewater work well for MAR purposes. Depending on the water quality and on the recharge technology, additional water treatment processes are required before the water recharges the aquifer.
This innovative technology allows the usage of the underground storage capacities as a water bank, where water can be deposited when available and withdrawn when required. Thereby, MAR secures water supply, contributes to climate adaptation, and dramatically increases drought resilience. Further, enhanced water availability allows for more agricultural irrigation and thus increases agricultural yield, which supports food sovereignty and socioeconomic development. Another advantage is the reduced surface run-off that reduces the risks of flood events and erosion.
MAR in Windhoek
Windhoek is the capital city of Namibia and serves as the economic, political, and cultural hub of the country. Windhoek is the center of economic activities in Namibia and hosts the main share of the country’s manufacturing activities, business and financial services (Mapani et al., 2023). According to the Namibian Statistics Agency's Quarterly Gross Domestic Product (GDP) report for the third quarter of 2021, the city of Windhoek contributed 21.6% to Namibia's GDP in that quarter. The services sector is the largest contributor to the city's GDP, accounting for 54% of the total, followed by trade and manufacturing sectors in 2022.
Aside from the challenges posed by climate change, increasing economic development and population growth in Windhoek puts further stress on the water supply. Murray et al. (2018) expects more than a doubling of the population from around 326,000 in 2018 to around 790,000 in 2050. While water supply in 2018 was around 27 MCM/year, in 2050 the demand is estimated to be around 50 MCM/a (Murray et al. 2018). These numbers indicate that a population increase of about 242% will be accompanied by a water demand increase of about 185% which implies a reduction of the per capita demand of around 24% from 83 MCM/year to 63 MCM/year. The closure of industries of Windhoek due to non-availability of water would bring dramatic economic losses of about US$ 1.5 million per day (Zheng et al. 2021). This could lead to huge social consequences such as unemployment, poverty, and hunger.
Due to these aggravated climate circumstances, the city of Windhoek already considered MAR in 1997 as an alternative to piping water from the distant Okavango River. First assessments and injection tests started subsequently. In 2004 NamWater, a public water utility in Namibia, conducted a study to investigate the feasibility of the MAR project including a cost-benefit analysis and a comparison with other alternatives as the construction of pipelines from the perennial surface water resources and the utilization of the far distant Tsumeb and Karst III Aquifers for emergency supply. Both alternatives are more expensive than the MAR approach. The water supply costs for the Tsumeb and Karst III Aquifer was estimated to be US$ 4.3/m³ and for the Okavango pipeline US$ 35.6/m³. The costs for the MAR scheme are US$ 2.0/m³ (Tuinhof et al., 2012). Since the MAR scheme turned out to be the most cost-efficient option, injection started in 2006 with six injection wells. To serve the increasing demand and to secure water supply, twenty further wells were constructed in 2011 and twelve additional wells in 2016 (Murray et al., 2018).
The major share of the water supply for the city of Windhoek is stemming from three dam systems (Omatako Dam, Swakoppoort Dam, and Von Bach Dam) that store and accumulate surface water during the rainy season when the rivers are carrying water. The water is then purified and distributed into the supply systems. Surplus water that is not required for the direct supply of the city is injected into the Quartzite Aquifer after its purification. Additionally, a water treatment plant purifies wastewater up to drinking water standards and enables its injection and usage. The aquifer conditions and its overlying geological layers protect the stored water against pollution and evaporation, which is a big advantage in comparison to a long-term storage with dams. In times when no surface water is available, extraction wells pump the water out of the aquifer and distribute it into the water supply system to serve the populations as well as the industry and agricultural needs (Tuinhof et al., 2012). This scheme consists of pumps, pipelines, treatment systems, and wells. The operation from 2006 to 2013 directly contributed to an increase of the water level and thus allowed higher sustainable abstraction rates.
The aquifer infrastructure is currently owned and operated by the City of Windhoek, while the water supply infrastructure is owned and operated by NamWater. To establish, manage, and operate a MAR scheme, knowledge and expertise is required and needs to be addressed to ensure an optimized, long-term utilization of the available resources and infrastructure.
MAR Solution Saves Namibia Amidst Aggressive Droughts by Serving as a Supply Backstop
From 2014 onward, Namibia has experienced a dry period with a reduction in precipitation rates, which also reduced the surface water availability. Thus, the recharge into the aquifer was intermittent and the groundwater levels dropped by around 40 meters because of the groundwater extraction. Without the recharge from 2006 to 2013, the abstractions would not have been possible at these numbers and the groundwater would now be at even lower levels. However, this shows that the scheme requires input, which is dependent on climatic conditions. If these conditions are not suitable for groundwater recharge (e.g., lack of precipitation and surface water availability), then the MAR scheme has to pause its operation until the conditions enable it. Thus, although the scheme improves drought resilience for the case of Windhoek, it should not be relied upon solely.
The MAR scheme of Windhoek functions as supply backstop, which ensures that the city is able to overcome prolonged drought periods that include a failure of surface water reservoirs. During rainy seasons, only 4% of the water supply comes from the aquifer and the main water source is surface water, which contributes around 76% to the water supply. This huge amount requires substitution during drought periods when no surface water is available.
Economic Potential
The MAR scheme lowers this risk of aquifer depletion significantly, further securing and improving the water supply situation. This allows the sustainable utilization of additional water resources and offers even further economic potential. For example, additional water for agricultural irrigation increases the agricultural yield and generates more jobs and higher incomes. The scheme also reduces the need to import expensive water from remote sources in the North. According to a study conducted by the International Water Management Institute (IWMI), MAR has increased crop yields by up to 50% in some areas of Namibia. In addition, MAR has enabled farmers to irrigate larger areas and diversify their crops, resulting in increased food security and income (Bekchanov et al., 2016).
MAR as a Reliable and Cost-efficient Option
MAR has proven to be a reliable and cost-efficient water augmentation option to serve the rising demand and to avert the threat of water scarcity reinforced by droughts and climate change. The scheme is cost-effective due to its ability to utilize existing infrastructure and the fact that the water treatment process is less energy-intensive than other conventional treatment methods. This facility — the water bank of the city of Windhoek — under the current dimensions is expected to be able to provide security for three years as the sole water resource during drought conditions (Murray et al., 2018). According to Murray et al. (2021), expanding the water bank storage to 61–71 MCM would allow for the extraction of approximately 19 MCM of water per year, further enhancing the capacity of the MAR scheme to meet the increasing water demand and provide a reliable and sustainable water source for Windhoek.
Diversifying Water Investment Infrastructure
The Windhoek MAR scheme's integration with alternative water supply options can offer a significant economic opportunity for investors. For instance, the integration of the MAR scheme with desalination can yield an economic internal rate of return (IRR) of approximately 94%, while the integration with the Okavango River transfer scheme can yield an IRR of around 68% (Murray et al., 2021). These IRR values significantly exceed the economic opportunity cost of capital of 10% and offer attractive investment options for investors. Moreover, this integration can provide improved water security and reliability for Windhoek, with desalination being capable of producing up to 26 MCM of water per year, as per the Windhoek Municipality's estimates. Therefore, the Windhoek MAR scheme's integration with alternative water supply options offers an excellent opportunity for investors to realize attractive returns while contributing to the city's water security and resilience.
Positive Net Present Value of the Project
To allow for future operation of the scheme, it is expected that the beneficiaries shall co-finance the operation over the economic lifespan of the project with US$ 115 million for operational costs and capital replacement over 30 years. This can be done via water expenses, which can be adopted according to the amount and usage. Despite a conservative set of assumptions, the project still yields a positive net present value, regardless of the choice of the water supply augmentation scheme in the future — whether it is desalination and transfer, or transfer from the Okavango River.
Conclusion and Way Forward
Namibia is grappling with a growing water scarcity issue due to severe changes in precipitation patterns and an arid climate — a condition only expected to worsen with climate change, making the country more susceptible to droughts. This poses significant challenges to the limited water supply, which will be exacerbated by the increasing water demand from population growth. Therefore, water resilience policies and programs are essential to withstand economic shocks and maintain socioeconomic well-being, given the country's vulnerability to water-related risks like droughts and floods.While agriculture plays a vital role in Namibia's economy employing more than 50% of the labor force, the scarcity of water directly limits agricultural productivity, aggravating the issue of food and social insecurity (World Atlas, 2023).
Windhoek is the center of economic activities in Namibia and hosts the main share of the country’s manufacturing activities, businesses, and financial services (Mapani et al., 2023). Besides the climatic situation, the increasing economic development and population growth of Windhoek put further stress on the water supply. Murray et al. (2018) expect more than a doubling of the population from 2018 to 2050, which will be accompanied by a water demand increase of about 185%. The relationship between water resilience and economic resilience in the case of Windhoek is a direct relationship. The closure of the industry of Windhoek due to non-availability of water would bring dramatic economic losses of about 1.5 million USD/day (Murray et al., 2021). This leads to huge social consequences such as unemployment, poverty, and hunger.
The MAR scheme in Windhoek has demonstrated itself to be a reliable and cost-efficient water augmentation option to serve the rising demand and to avert the threat of water scarcity being exacerbated by droughts and climate change. The scheme has increased drought resilience and further secured and improved the water supply situation, allowing the sustainable utilization of additional water resources and offering economic potential. Conducting a cost-benefit analysis and pilot testing before scaling proved to be a critical success factor for the process. It enabled the accurate measurement of results and performance, providing access to crucial insights. Nevertheless, a MAR scheme is limited by the storage capacity of the aquifer and its requirement for water recharge, despite its effectiveness in buffering prolonged drought periods.
Windhoek aims to further diversify its water resources and promote integrated resource management to ensure a sustainable water supply for the future. This can take place by combining technological approaches and water management strategies. Along with the MAR scheme, which has already demonstrated reliability and cost-effectiveness, enhancing the water treatment plant's treatment and injection capacities could enhance the city's water supply. Further, Windhoek has integrated water-saving measures and rooftop rainwater harvesting technology, while also exploring options such as expanding the aquifer's storage capacity and increasing the water injection rates for aquifer recharge. Mapani et al. (2023) suggest drilling more deep wells to expand the storage capacity of the MAR scheme, and verifying if the water treatment plant can handle an increased capacity beyond its current 40% grey water recycling rate.
The drought index strategy is one of the implemented water-saving measures, targeting a 35% reduction in water usage. For the water scarcity and drought programs to be successful in Namibia, they should be staged for severity and intensity. Programs should also identify protected groups, ecosystems, and sectors and be revised regularly to incentivize adjustment to evolving extreme events.
Economic resilience requires active participation from both the public and private sectors. It is essential for the public sector and significant public finance, investment, and regulatory bodies to articulate a clear vision of the goals and strategies for economic resilience. Thus, integrated water planning and coordination across all sectors is vital for navigating these challenges. Overall, a comprehensive and urgent approach is necessary to address the challenges of increasing water demand and varying water availability resulting from expected climate changes.
References
Bekchanov, M., P. van der Zaag, H. Savenije, P. Martínez-Santos, and L. Rodriguez-Sinobas. 2016. “A framework for managed aquifer recharge implementation and evaluation under data-scarce conditions: Methods and application to Khorezm, Uzbekistan.” Agricultural Water Management, 176, 18-28.
IPC. 2021. “IPC Acute Food Insecurity Analysis October 2021 - March 2022.” https://www.ipcinfo.org/fileadmin/user_upload/ipcinfo/docs/IPC_Namibia_AcuteFoodInsecurity_2021Oct2022March_Report.pdf
Mapani, Benjamin S., Rosemary N. Shikangalah, and Asteria L. Mwetulundila. 2022. "A review on water security and management under climate change conditions, Windhoek, Namibia." Journal of African Earth Sciences: 104749.
Department of Water Affairs. 2010. Water Banking: A practical guide to using Artificial Groundwater Recharge. Pretoria: Department of Water Affairs, South Africa.
International Trade Administration. 2023. “Namibia Country Commercial Guide.” https://www.trade.gov/country-commercial-guides/namibia-agricultural-sector?navcard=9843
Murray, R. 2008. Artificial Recharge: The intentional banking and treating of water in aquifers. Lecture notes prepared for the Department of Water Affairs and Forestry. Pretoria, South Africa.
Murray, Ricky, Don Louw, Ben van Der Merwe, and Immo Peters. 2018. "Windhoek, Namibia: from conceptualising to operating and expanding a MAR scheme in a fractured quartzite aquifer for the city’s water security." Sustainable Water Resources Management 4: 217-223.
Murray, R., B. Van der Merwe, and P. van Rensburg. 2021. “Case Study 13: A Managed Aquifer Recharge Scheme in a complex fractured quartzite aquifer for securing water supply to Windhoek, Namibia.” In Managing Aquifer Recharge: A Showcase for Resilience and Sustainability edited by Zheng, Y., A. Ross, K.G. Villholth, and P. Dillon . Paris: UNESCO.
Namibian Statistics Agency. 2021. “Quarterly Gross Domestic Product Q3 2021.” https://nsa.org.na/publications/statistical-reports/economic-statistics/gross-domestic-product-quarterly-statistics
Tuinhof, A., F. Van Steenbergen, P. Vos, and L. Tolk. 2012. Profit from Storage. The costs and benefits of water buffering. Wageningen: 3R Water Secretariat.
UN. 2017. “SDG 6 snapshot in Namibia.” https://www.sdg6data.org/en/country-or-area/namibia
UN Stats. 2019. “National Experience on Water Statistics.” https://unstats.un.org/unsd/envstats/meetings/2019-Namibia/documents/Session%205.1.1%20Water%20Statistics%20Namibia.pdf
UNDP. 2022. “Women & girls towards resilience environmental risks.” https://www.undp.org/namibia/news/women-girls-towards-resilience-environmental-risks
Van Rensburg, P. 2021. “Survival of a City: Drought Mitigation through Unconventional Water Supply.” Presentation at the Water Pavilion at COP 26 Session: Mitigating floods and droughts innovative approaches for closing urban water cycles.
World Atlas. 2023. “The Biggest Industries in Namibia.” https://www.worldatlas.com/articles/which-are-the-biggest-industries-in-namibia.html
World Economics. 2023. “Namibia’s Gross Domestic Product (GDP): New Estimates For Gross Domestic Product Adjusted for Base Year and Informal Economy.” https://www.worldeconomics.com/Country-Size/namibia.aspx