A Review of Climate Change Impacts on Water Resources and Adaptive Strategies: A Case Study of Windhoek in the Namibian Context

© The Author(s) 2025. Published by AMO Publisher. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https:// creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. A Review of Climate Change Impacts on Water Resources and Adaptive Strategies: A Case Study of Windhoek in the Namibian Context Aina Ndinelago Shikongo  College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; UNEPTongji Institute of Environment and Sustainable Development, 1239 Siping Road, Shanghai 200092, China Precious S. Sebego College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; UNEPTongji Institute of Environment and Sustainable Development, 1239 Siping Road, Shanghai 200092, China Article History: Received: 18.10.2025 Revised: 13.11.2025 Accepted: 14.11.2025 Published: 18.11.2025 Abstract The study presents a comprehensive review of the impacts of climate change on water resources and adaptive strategies, with a specific focus on Windhoek, Namibia, a semi-arid urban area facing severe water scarcity. Climate change is altering global water cycles, intensifying hydrological extremes such as droughts and floods, which threaten water availability, quality, and management globally. Namibia is one of the world's most arid countries, with rising temperatures, erratic and declining rainfall, and high evaporation rates severely limiting surface runoff and groundwater recharge. Windhoek depends on a combination of distant dam systems, groundwater, and pioneering direct potable reuse to meet its water needs. Managed Aquifer Recharge (MAR) is a critical component of its integrated water resource management strategy, enhancing resilience during droughts by storing treated water underground. The city has reduced per-capita water consumption through strict demand management policies while expanding capacity in reclaimed water and artificial recharge. Despite these efforts, rapid urban growth and climate variability continue to challenge water security. The review underscores the importance of integrated approaches combining technological innovation, ecosystem-based adaptation, policy support, and stakeholder engagement to build resilience. It highlights adaptive measures such as rainwater harvesting, improved irrigation, and watershed management as essential for mitigating climate-induced water stress. Water scarcity threatens Windhoek's economic resilience, food security, and social wellbeing. Namibia should diversify water sources, expand MAR capacities, strengthen institutional frameworks, and advocate for regional cooperation for sustainable water supply. This review offers critical lessons on managing water scarcity through integrated climate-resilient approaches in Namibia. Keywords: Adaptive strategies, Climate change impacts, Namibia, Water management, Windhoek. Suggested citation: Shikongo, A.N., & Sebego, P.S. (2025). A Review of Climate Change Impacts on Water Resources and Adaptive Strategies: A Case Study of Windhoek in the Namibian Context. European Journal of Theoretical and Applied Sciences, 3(6), 134-146. https://doi.org/10.59324/ejtas.2025.3(6).13 www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 135 Introduction This review paper focuses on how climate change affects water supplies and adaptation measures. Windhoek is a prime example of a semi-arid urban centre with limited water resources that faces urgent water management issues brought on by climate change (Mapani et al., 2023). Windhoek, Namibia’s capital, serves ~15% of the national population and epitomizes the challenges and innovations in urban water security under climate stress (Mapani et al., 2022). The city depends on a combination of surface runoff, groundwater from the Windhoek aquifer, and recycled wastewater for its domestic and industrial water supply (van der Merwe, 2009). However, climate-induced declines in precipitation and high evaporation have severely limited natural recharge, yielding only ~2 Mm³ annually from the Windhoek aquifer and have degraded its sustainability, resulting in declining groundwater levels (Maher et al., 2025). In response, Windhoek has adopted several advanced strategies. Windhoek pioneered potable reuse, operating the world’s first DPR scheme since 1968. Water availability, quality, and management techniques are all significantly impacted by climate change, which presents serious problems to water resources in Namibia. Therefore, this detailed review analysis intends to unpack the climate change impacts on water resources in Namibia and the relevant adaptive strategies to ensure water availability and security in Namibia. Materials and Methods Overview of the Study Area: Windhoek, Namibia Windhoek is the capital city and the only city in Namibia, and based on the Namibia National Statistics Agency (NSA), the city had about 325,858 inhabitants in 2011 (National Statistics Agency, 2011). Windhoek is situated on Namibia’s central plateau at an elevation of approximately 1,650 m, flanked by rocky, mountainous terrain to the south, east, and west. The information was adapted from Mendelsohn et al. (2002), Atlas of Namibia. It determines landscape by tectonic events, geological composition, water, erosion, deposition, climate, soil, and vegetation, all of which collectively shape the visible features of an area of land (Figure 1). This topography restricts urban development outward, making the flat Breakwaters area to the north the most feasible zone for expansion. Current estimates put the population well over 400,000 (World Population Review, 2022). Windhoek is currently the centre of economic activities, offering more than 50% of the country's manufacturing activities, business, and financial services (Mapani and Schreiber, 2008). Namibia, bordered by the Kalahari Desert and Namib Desert, has several perennial rivers, including the Orange, Kunene, Zambezi, and Okavango, with over 90% of its territory classified as semi-arid, arid, or hyper-arid. (Mendelsohn et al., 2002; Shanyengana et al., 2004; Barnard, 2012). As the driest country in Africa south of the Equator, Namibia experiences limited precipitation and frequent droughts, which have become typical across much of the country. The average annual rainfall remains low and highly variable (Fig. 1), with evaporation rates reaching around 83% (Mendelsohn et al., 2002; Bravenboer, 2004; Lahnsteiner and Lempert, 2007; City of Windhoek (CoW), 2017; Mostert, 2017; Lohe et al., 2020), rendering Namibia water-stressed. Up to 65% of the water supply is sourced from boreholes, while only 35% comes from surface water sources (Namibia Water Corporation, 2017). Climate in Windhoek Windhoek has a hot semi-arid climate, with over 300 sunny days per year. Annual mean temperature is around 19–19.5 °C. The hottest month is December (~31–32 °C), coldest is July (~15 °C) (Steyn, 2021). Average annual rainfall ~350–360 mm, highly variable, with periodic droughts and intensely dry winters and wetter summers. Extremely high, around 83% of rainfall is lost to evaporation, only ~2% becomes surface runoff, and ~1% contributes to groundwater recharge (Atlas of Namibia, 2002). www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 136 Figure 1. The landscape of Namibia. Source: Atlas of Namibia The flow chart in Figure 2 provides a detailed description of the articles reviewed in this study. It was confirmed that every search result was exactly on the topic of climate change, water resources and adaptive measures in Windhoek and Namibia. The total number of articles reviewed was one hundred and fifty-four. Twenty-three papers were obtained from the Scopus database, seventy papers from the Web of Science, and around 14 papers were excluded from this study because they were outside of the search topic and specific objectives. This was justified for this study to reduce bias in the analyzed data and to ease data collection. Figure 2. Flowchart for the Selection of Reviewed Literature Reviewing Climate Change Impacts on Water Resources Climatic changes in Windhoek and Namibia due to increased frequency and intensity of droughts, rising temperatures, drop in precipitation patterns, and evapotranspiration shifts all contribute to reduced water availability and more erratic water supplies (Spear et al., 2018). These effects aggravate water scarcity and stress already vulnerable water systems, particularly in arid and semi-arid regions such as Namibia (Shikangalah, 2020). Windhoek, the capital of Namibia, is a leading example of water scarcity management in an arid environment facing climate change impacts. Namibia's climate is characterized by low and variable rainfall and high evapotranspiration rates. Increased drought frequency and severity, along with rapid urbanization and population growth, place enormous pressure on Windhoek’s water resources (Mapaure, 2022). 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 the 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. Windhoek’s water supply in a climateconstrained future According to vulnerability assessments for Namibia, climate change will increase the temperatures by 1-4 degrees; rainfall will decrease by about 20 percent, but increase in intensity (Wilhelm, 2013). The recent past demonstrates this pattern: unusually high intensity rainstorms were recorded in 2004, 2006, 2008, and 2011, while abnormally dry years were recorded in 2013, 2015, and 2016 and in 2016, for the first time, the dam serving as the www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 137 main source of water for Windhoek received no inflows. Adaptive Strategies for Water Resource Management Increasing system resilience through a combination of supply-side and demand-side tactics is necessary for adaptive management of water resources in the face of climate change. One of them is pumping cleaned surface water into aquifers during rainy seasons so that it can be extracted later during dry spells. MAR enhances groundwater storage and provides a buffer during dry spells (Page et al., 2018). Adopting water-efficient irrigation techniques, utilizing greenhouses, adjusting planting dates, and conserving soil moisture and greywater can reduce agricultural water demand and dependency on conventional sources. (FAO, 2012). Since no single action may completely alleviate climate-induced water stress, integrated approaches combining various strategies are crucial. The socioeconomic environment, stakeholder participation, and financial resources are also necessary for successful adaptation. Integrated Urban Water Management (IUWM) Strategies Windhoek has diversified its water sources as part of a multifaceted, integrated strategy surface, groundwater, reclaimed, and MAR (Scott et al., 2018). Water Demand Management, which includes lowering prices, raising public awareness, and enforcing water-saving laws that forbid washing cars or gardens. MAR and wastewater reuse investments provide long-term cost-effectiveness and sustainability (Olivieri et al., 2018). Master planning and drought contingency frameworks, with strategic guidelines for infrastructure and resilience planning as well as policy and organizational innovation, are needed. Water Sensitive Urban Design (WSUD) implementation faces challenges such as limited institutional capacity, a lack of policy frameworks, and fragmented governance. Challenges and Future Directions There are still issues, even though Windhoek's MAR and IWRM programs show successful adaptive tactics. Continuous attention is needed for infrastructure maintenance, reliance on weather for recharge, and the requirement to scale with increasing demand. According to climate projections, drought conditions are expected to intensify, requiring ongoing innovation and funding for adaptive water technology and policy (Duda, 2017). Climate change significantly impacts water resources, particularly in vulnerable dry regions. Building resilience requires adaptive techniques like crop management, water conservation, irrigation, and controlled aquifer recharge. Windhoek, Namibia, demonstrates these challenges and achievements. Results Supplying Windhoek with Water NamWater supplies most towns and cities with bulk water, but Windhoek supplements this supply with its own groundwater sources and reclaimed water, especially following years of poor rains (City of Windhoek, 2018). Various and alternative sources are then used in greater amounts, and measures are implemented to control or reduce the demand for water. Figure 3 shows the volumes of water supplied from different sources to Windhoek from the year 1938 to 2018. Figure 3. Volumes of Water Supplied from Different Sources to Windhoek, 1938–2018. Source: City of Windhoek, 2018 The water supply in Windhoek is a combination of conventional (groundwater and surface water) and unconventional (reusing semi-purified and reclaimed water) sources, as well as interventions (artificially recharging its aquifer). Increasing www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 138 block tariffs, water-saving initiatives, and water restrictions have all been used to lower demand during recurring droughts, such as those that occurred in 1980–1982, 1994–1996 and 2015– 2019. During those droughts, groundwater demand rose, and reclaimed water became more significant; in 2018, it accounted for 26% of Windhoek's potable water supply. Water Access, Demand and Supply In Namibia, providing water is difficult due to two realities. The first is the overall lack of water because of poor rainfall and high evaporation. The second is that a lot of people live in places that are far from naturally occurring water sources. As a result, water is frequently transported over long distances, making its provision a costly endeavor. A variety of unconventional sources are employed to address Namibia's water supply issues, including desalinated saltwater, wastewater that has been cleaned for drinking and used for irrigation, and the artificial recharging of Windhoek's aquifer through the injection of treated water from Von Bach Dam. In 1968, Windhoek was the world's first large city to implement direct potable reclamation, a process that ensures cleaned wastewater is adequately Access to Clean Water since 1991 The availability of potable, or clean, drinking water has grown dramatically in the last few decades. As shown in Figure 5, the percentage of families with access to safe drinking water increased from 60% at independence in 1991 to 80% in 2011. It was anticipated that 94% of Namibian households would have access to drinkable water by 2016. Compared to rural families, a significantly greater percentage of urban households (98%) had access to safe drinking water in 2011. (63 per cent). By 2016, access had further increased, with 85% of rural households and 99 percent of urban households having access to safe drinking water (NSA, 2016). Groundwater Resource In Namibia, many farms, communities, and smaller towns rely only on groundwater as their primary source of water (Lewis & Claasen, 2018). Additionally, groundwater plays a significant role in the overall water supplies to Swakopmund, Walvis Bay, Arandis, and Windhoek. It also supplies all of the water consumed by certain major cities, including Grootfontein, Tsumeb, Otjiwarongo, Lüderitz, and Henties Bay (Bann & Wood, 2012). For Namibia, groundwater is an essential source of water, and its significance increases during dry spells. Although a large portion of it is being drawn from deep aquifers, spring water and hand-dug wells have long been essential sources of water in Namibia's interior. Figure 4. Percentage of Household Access to Safe Drinking Water in Namibia, Urban and Rural Areas from 1991 to 2016 Source: Namibia Statistics Agency's (NSA's) 2016 Figure 5. Groundwater to the Surface. The One Here at Gobaub in Etosha National Park has Probably Supplied Water for Tens of Thousands of Years to Wildlife and People Source: Photo by (J. Mendelsohn) Groundwater rises to the surface through artesian springs. Some, like this one at Gobaub www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 139 in Etosha National Park (Figure 5), have likely provided water to people and wildlife for tens of thousands of years. Although the quality and availability of groundwater resources vary greatly, they are not all created equal. While some are fresh and abundant, others are brackish, dry up periodically, or are hard to get to. Many of us have a poor understanding of groundwater, which is hidden from view. Long-term monitoring and a solid understanding of geology and aquifers are necessary to determine how much is present in a given location, how deep it is, where and how it is refilled, and how to abstract it safely and sustainably. Major Aquifer Types, Supply Potential and Direction of Groundwater Flow This map in Figure 6 offers a glimpse of an underwater environment that is invisible above ground. Water is held in fractured and porous aquifers; some have very little water, while others have an abundance that is unthinkable in such a dry climate. Ohangwena II, the Karst, Koichab, Kuiseb, Maltahöhe, Omdel, Stampriet, and Windhoek aquifers are among Namibia's most abundant aquifers. Figure 6. Aquifer Type, Potential, Yield and Human Activities Source: Namibia Atlas Surface Waters There are no perennial rivers close to Windhoek. Its primary source of surface water is the Grootfontein-Omatako Eastern National Water Carrier, which transports water from aquifers and far-off ephemeral rivers some 450 kilometers to the north. Depending on the source, this supplies between 70 and 95 percent of the city's water through the Omatako, Von Bach, and Swakoppoort dams (Atlas of Namibia, 2002). A key component of Windhoek's supply is the von Bach Dam, which is situated on the Swakop River and has a capacity of about 48.6 million m³. Under normal circumstances, the three-dam system can meet 70–75 percent of demand; when the national carrier system is included, this number can reach 95 percent. In addition to providing water, many of these ephemeral and perennial wetlands are significant productive ecosystems that sustain a wide variety of flora and fauna. There are various types of surface water flowing rivers that may have associated floodplains, swamps or marshes, deltas or river mouths. Natural, well-vegetated standing waters, such as swamps, vleis, springs and seeps. Figure 7. The Hydrological Catchments, Gauge Stations, Major and Minor Ephemeral Rivers Source: Mendelsohn, et al., 2002; Atlas of Namibia Rainfall Patterns Rainfall is the most crucial element for maintaining life and livelihoods in a country as www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 140 arid as Namibia. Seasonally, annually, and geographically, it varies significantly. The annual falls are crucial for restoring Namibia's finite freshwater resources, sustaining native flora, assessing crop yields, and assessing how well domestic and wild animals reproduce and raise their young. An overview of the patterns of rainfall during the summer rainy season is given by the maps in Figure 8. This more thorough analysis emphasizes variations in the distribution of rain from east to west and north to south. The average monthly rainfall in each latitude and longitude degree square is displayed on each graph. For most areas in Namibia, almost all rain falls in spring and summer between September and April. The only exception is in the southwest, which lies in the winter temperate rainfall belt; here, monthly totals are similar throughout the year. Within the summer rainfall area, there is a clear trend linked to the movement of moist air. In the northeast rains start earlier, and peak months are December to February. Rain starts later in the south and west, with peak months from January onwards. On average, February and March are the months with the highest falls over the southern and western thirds of Namibia. Along the entire coast, rainfall is generally very low. Figure 8. Rainfall Patterns Throughout the summer Rainy Season in Namibia since 1901/02–2019/2021 Source: Namibia Meteorological Services, 2021 Rainfall fluctuates from season to season. These graphs Figure 9 of monthly rainfall in Khorixas, Tsumkwe, and Katima Mulilo for five consecutive seasons from 2015–16–2019–20 demonstrate this, which is true for the majority of Namibia. They exhibit a great deal of variance in monthly rainfall totals, rainfall distribution throughout the seasons, and the months with the most precipitation. The timing and consistency of rainfall events must be somewhat stable for crop farming to be successful, yet Namibia's natural rainfall variability frequently results in crop failures or renders dryland cropping unfeasible. Figure 9. Seasonal Rainfall Patterns in Some of the Places in Namibia Source: Namibia Meteorological Services, 2020. Climate Change There are two distinct components of climate change. First, sea levels have been increasing and the Earth has been growing hotter. Those patterns will undoubtedly persist. Second, it is challenging to forecast the precise impacts of climate change on other facets of the environment and weather. This is not to downplay the urgency of reducing humaninduced global warming, nor the myriad potential and detrimental consequences of www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 141 climate change. Climate change is projected using Representative Concentration Pathway (RCP) scenarios. These models evaluate how various concentrations of greenhouse gases affect the radiant energy that the Earth receives and emits. Scenario 8.5 of the RCP is shown on the maps below. According to this scenario, the present rate of increase in greenhouse gas emissions per Projected Rainfall, 2040–2060 Compared to historical rainfall from 1960 to 1990, Namibia's total annual rainfall is predicted to drop by almost 9% between 2040 and 2060. Rainfall is predicted to decrease by 8% during the rainy season (October to April) and by 20% during the dry season (May to September), making all months of the year drier. Figure 10. The Projected 2040-2060 Change in Rainfall Distribution across Namibia Source: Atlas of Namibia Figure 11. The Projected 2040-2060 Change in Temperature across Namibia Source: Namibia Atlas Projected Changes in Temperature by 2060 Temperatures are expected to increase progressively as one moves eastwards from the coast. Mean annual temperature across Namibia is projected to increase by 3 degrees Celsius, with all months of the year becoming substantially warmer. Adaptation and Mitigation Measures for Water Availability An interdisciplinary and comprehensive approach involving policymakers, scholars, practitioners, and the public and private sectors is required to develop workable and successful adaptation and mitigation plans for Namibia and Windhoek city (Turyasingura et al., 2022). The survival of many African regions is threatened by the many shortand long-term effects of climate change on the water on ecosystems and populations in Windhoek and Namibia as a whole, ranging from social and economic repercussions to food and health shortages (Fuso Nerini et al., 2019). Vulnerability, on the other hand, differs depending on individual countries’ geographical location and their ability to mitigate or adapt to changes (Thomas et al., 2019). In order to adjust to these changes, Windhoek and Namibia's water resources must be rethought in light of climate change. This includes, but is not limited to, ensuring water availability through an integrated approach founded on the nations' cooperation and ensuring the sustainability of water resources through effective management. It is also important to support mitigation efforts that strengthen Namibia's robust institutions and infrastructure (Fuso Nerini et al., 2019). Integrative Approach to Adapt to Continental Water Resources Crisis An integrated strategy for the water resources crisis is a bilateral and international collaboration between countries, particularly African countries, to address the issue of shared water (Fan et al., 2020). In addition to collaboration, this entails the use of technology, good communication, the creation of a water climate information network among African nations, and legally enforceable agreements. This makes it possible for nations to work together to solve www.ejtas.com European Journal of Theoretical and Applied Sciences (ISSN 2786-7447) 2025 | Volume 3 | Number 6 142 and benefit from the results of water use by taking into account one another's demands, advantages, disadvantages, and rewards. cooperation, contingent on the level of compromise reached by each nation that shares its rivers. Access to clean water and the avoidance of water contamination are two advantages that could result from international cooperation (Grech-Madin et al., 2018). Integrated Water Resources Management and Infrastructure This relates to the concepts of Integrated Water Resources Management (IWRM), which require the support of suitable institutional frameworks and policies to manage water resources effectively and efficiently (in both present and future climates) (Al Jawad et al., 2019). The reality of Windhoek, Namibia's current institutional arrangements, should be carefully taken into account when modifying these strategies. More than 68% of all Nationally Determined Contributions list new and retrofitted water infrastructure including surface reservoirs, multipurpose dams, soil moisture conservation strategies, natural wetlands, rainwater harvesting for storage and infiltration, urban green spaces, conjunctive use of surface and groundwater, managed aquifer charge, and source water as a priority for adaptation action (NDCs) (Wang et al., 2019). Water Harvesting Water harvesting is the process of collecting rainfall directly from the sky (Tu et al., 2018). This can be used as a strategy and water availability measure in the suburbs of Windhoek. Rainwater can either be recycled back into the groundwater system or collected and stored for later use. Rain is a vital source of water for humanity since it is the first type of water in the hydrological cycle that people are aware of. Rainwater harvesting comprises watershed management, catchment runoff, rooftop runoff, and seasonal flooding from nearby streams (Bennett & Barton, 2018). Therefore, there is a need for rainwater harvesting in Uganda, especially in Kigezi and Northern regions, to keep water during dry seasons for both domestic use and irrigation to increase productivity, as shown in Figure 12. Figure 12. Conceptual Sketch of Rooftop Rainwater Harvesting System Source: http://www.eng.warwick.ac.uk/DTU/rainwa Managed Aquifer Recharge (MAR) as a Climate Adaptation Measure Intentional water recharge to aquifers for future recovery or environmental benefit is referred to as MAR. By storing water underground and using it during dry seasons, it thereby benefits from excess water resources during flood times. In contrast to surface water reservoirs, aquifers offer superior protection against pollution and evaporation, which is crucial in dry and semi-arid areas. People's livelihoods are threatened by droughts, floods, and heavy rains because of either an excess of water or a shortage. One important adaptation tactic in these circumstances is the storage of water in constructed or natural infrastructure. Aquifers are naturally occurring water reserves that MAR can "enhance" intentionally. Intentional water recharge to aquifers for future recovery or environmental benefit is referred to as MAR. By storing water underground and using it during dry seasons, it thereby benefits from excess water resources during flood times. In contrast to surface water reservoirs, aquifers offer superior protection against pollution and evaporation, which is crucial in dry and semi-arid areas. This diagram on Figure 13 illustrates the link between the Auas Mountains and Windhoek and how groundwater levels dropped after the 1950s, thus creating a cone of depression which could be recharged by injecting treated water from Von Bach Dam (Murray et al., 2021).