Despite repeated commitments to universal access to water, energy, and food, most developing countries continue to face challenges to the security of these strategic resources and struggle to achieve the related Sustainable Development Goals (SDGs 2, 6, 7). We assessed the state of the water-energy-food (WEF) nexus at sub-national scales in South Africa (Inkomati Usuthu Water Management Area) and Zimbabwe (Mzingwane Catchment), employing a mixed-methods approach that included (i) a literature review, (ii) stakeholder engagement, (iii) observations and (iv) modelling. The key inputs in the iWEF tool were pairwise comparison matrices (PCMs) developed from key WEF-related expert stakeholders’ pairwise judgements of the six iWEF model indicators. Inkomati Usuthu Water Management Area and Mzingwane Catchment had WEF nexus composite indices of 0.209 and 0.189, respectively, indicating that the management of WEF resources is moderately sustainable. The irregular shape of the centrepieces in the spider diagram in the iWEF tool is symptomatic of an overall imbalance in the management of WEF resources in the Inkomati Usuthu Water Management Area and the Mzingwane Catchment. These findings provide entry points for prioritised interventions to improve resource security. Still, these should be planned and implemented from a nexus perspective to optimise synergies and minimise trade-offs and risks. With the two case studies located in arid and water-scarce regions, opportunities for improving WEF security lie in managing available resources from a nexus perspective. Decentralised and off-grid solutions should also be considered, especially in rural areas where most of the population lives in the Inkomati Usuthu Water Management Area and the Mzingwane Catchment. To conclude, southern African countries share a similar history, context, and WEF-related developmental challenges. It can be inferred that their sub-national scales are in moderately sustainable states of the WEF nexus, which require nexus planning for integrated, contextualised solutions to improve collective WEF security for all.

Recent developments of higher-resolution and lower-latency reanalysis data allow mapping reference evapotranspiration (ET_o) over large areas in a near real-time manner. This study evaluates the ERA5, AgERA5 and GEOS5 reanalysis datasets for meteorological input in Africa and Southwest Asia by comparing between data products and with 174 in situ sites. The inter-comparison reveals non-stationary differences between datasets and highlights temporal inconsistencies in the GEOS5 data. When evaluated against in situ measurements, GEOS5 demonstrates lower accuracy compared with ERA5 and AgERA5. Additionally, while all datasets accurately estimate air temperature and pressure, they overestimate windspeed and solar radiation, and underestimate vapour pressure. The propagation of uncertainty estimates of ERA5 through the FAO56 ET_o equation shows particularly high uncertainty in the tropics. This study emphasizes the importance of applying multiple uncertainty assessment methods for better-informed use of reanalysis data, especially in data-scarce regions.

The water-energy-food (WEF) nexus concept has emerged over the last decade as a way of thinking about and analysing natural resources. Each WEF sector has intimate feedback relationships with the other sectors, forming a coherent, complex system. Through analysis of these relationships and of the impact of policy on the system, more integrated and sustainable resources management is aimed for. The nexus concept is not without criticism, and a concern is that one sector would come to be seen as ‘more important’ than the others. This paper attempts to break such ideas, describing how each WEF sector is equally essential for the functioning of the other two, and that the WEF nexus is more than the sum of its parts. Going further, the paper shows how the WEF nexus is supported/enabled by ‘ecosystems’. Without good ecosystems functioning, the WEF sectors could be compromised with significant consequences. At the same time, ecosystems are degraded by WEF demand and exploitation. Society depends upon ecosystems and the proper quantity, quality, timing, and spatial availability of WEF resources. Societal demand impacts on WEF resources availability and security, and on ecosystems integrity. The paper concludes by stating that the integrity of this WEF-ecosystems system is under significant threat as planetary boundaries are exceeded, ecological overexploitation is accelerating, and global warming impacts become acute. Nothing short of a wholesale societal behavioural and conceptual shift towards WEF sectors, their use, exploitation, and management is required, and that a systems-thinking mentality is central to such a shift.

Policy siloes between national adaptation plans (NAPs), nationally determined contributions (NDCs) and sustainable development hinder effective climate action and resource governance in East Africa. Further, rapid population growth and climate change impacts intensify demands for water, energy, and food (WEF), fuelling resource exploitation. This study employs a mixed-qualitative methodology using document analysis, and semi-structured interviews to examine the interlinkages between NAPs, NDC and regional development priorities. Results show implied connections between policy instruments, sustainable development, and climate action form the crux of WEF interlinkages. In practice, incoherence between these instruments create competition and trade-offs that increase WEF resource security. For example, the focus on food security, mostly through extensification, has created tradeoffs with water and energy security, undermining development goals. There are implicit interlinkages in policy and, to a certain extent, in practice. Although insufficient, these are foundations for a bottom-up approach to implementing integrated climate action commitments. Understanding the interconnectedness and interdependencies between sector policies, climate actions, and supranational development plans could catalyse and accelerate sustainable development while building resilience, through a multi-sectoral approach. We posit the need for a transdisciplinary, WEF approach to catalyse cooperation for development and climate action in East Africa. Ultimately, a transdisciplinary approach focused on equity, social justice, sustainability, and a just transition is required to support development agendas.

Jordan’s Amman-Zarqa (AZ) basin faces increasing water scarcity due to increasing demands and persistent groundwater over-abstractions for irrigation. To address this issue, water conservation has been set as a national strategy, and several initiatives aiming to conserve water in irrigated agriculture have been implemented in the basin’s highlands. This study evaluates the impact of water conservation technologies (WCTs) on irrigation water savings in the AZ basin highlands. Monthly data on irrigation application were collected from 22 farms over three crop seasons (2019–2022) for four dominant orchards. Farm-scale water savings were calculated and projected to the basin scale under two scenarios: a sustainability scenario aligning groundwater abstraction with irrigation needs under WCTs and an economic scenario expanding irrigated areas using the saved water. Results show that irrigation efficiency before the influence of WCTs was below 55%, with farmers applying an average of 1277 mm/year. After implementing WCTs and farmers fine-tuning their irrigation practices, irrigation application decreased to an average of 795 mm/year, resulting in 38% water savings. Projecting these savings basin-wide, WCTs could conserve 44 Mm³/year of water under the sustainability scenario. The results provide a solid basis for informing water conservation targets in this region. However, successful water conservation using WCTs depends on farmer-led testing to ensure reduced irrigation does not compromise crop yields. Pilot programs supported by trusted technical advice through farmer field schools and appropriate incentives can achieve sustainable water conservation in this region. Concurrently, monitoring is required to regulate irrigation expansion as it could undermine water savings.

Co-creation is seen as instrumental in bridging the gap between scientific innovation in climate services and their use in decision-making. However, there has been limited engagement with the different types of co-creation approaches that exist in practice, how they are executed, how they bridge the usability gap, and in what situations they would be most effective. This study aims to characterise climate service co-creation in practice, and develop typologies to explore how they bridge the usability gap. We conducted Thematic and Ideal Type Analyses of 33 case studies developed from Key Informant Interviews and Content Analysis of co-creation process documents. We show that i) co-creation approaches place a strong emphasis on the climate information (its usability and usefulness) to improve use of climate services, ii) co-creation in practice deviates from the theoretical approach, and iii) in addition to other contextual factors, the mode (research and commissioned) of co-creation has a strong influence on the execution of co-creation processes. We develop three typologies of climate service co-creation in practice; i) information-intensive (n = 21), concerned with producing useful information; ii) functional-use intensive (n = 5), concerned with the usability of the co-created information in decision-making; and, iii) innovation-oriented (n = 7), concerned with embedding new insights into innovative climate services. This study benefits researchers and practitioners implementing co-creation in the field of climate services to understand the types of co-creation that exist, the risks associated with each type, and the level to which each type may influence the use of climate services.

Water, energy, and food resources are closely related in the water-energy-food (WEF) nexus, a tightly connected system in which impacts in one sector leads to changes in the other sectors. The WEF nexus approach studies these interactions to better understand their connections and implications across sectors, and is focused on making research practicable for policy. There is a clear lack of policy coherence studies to provide practical recommendations to achieve integrated resources management. This is true in the Tana River Basin (TRB), which provides abundant water, energy and food resources to the national economy and development of Kenya. This work carried out a WEF policy coherence assessment of the Tana River Basin. Results show that there are synergies and trade-offs across all resources sectors and their policy objectives. Water policies (e.g. to secure water availability) are generally evaluated as win-win, thus being supportive of attainment of goals in other policy sectors. Food policies (e.g. to develop the agricultural sector) show the highest number of trade-offs, suggesting these policies could be redesigned to minimise the trade-offs with other resource policies. This work highlights specifically which policies are relatively more or less supportive for holistic resources management in the TRB. In particular, the only TRB-level policy analysed (which is cross-resource in its ambition) shows synergies with national policy, offering opportunity for leveraging benefits and increasing implementation efficiency across resources. Strengthened cross-sectoral collaboration, joint workshops, and the establishment of a national cross-sectoral taskforce to develop aligned policies are recommended. This work provides a basis for similar studies across Africa, and promotes research that is of practical relevance.

Attention on the use of transboundary aquifers (TBAs) and their cross-border impacts is growing as countries become increasingly concerned about their long-term water security. Cross-border impacts, in groundwater quality and quantity, tend to concentrate in specific parts of TBAs, as they largely depend on the transboundary flow dynamics where anthropogenic actions operate. Thus, there is a growing consensus that strategies intended to prevent or mitigate such impacts should be implemented in strategic zones rather than in the whole TBA. These transboundary groundwater management zones (TGMZs) are relatively recent but have become a prominent topic in TBA management. However, until now, limited effort has been put into exploring the concept of TGMZs and the methods for their delineation. This research aims to fill these gaps and provide a basis for the delineation of TGMZs, thus helping neighbouring countries meet international responsibilities regarding the right to use and enjoy groundwater in TBAs. By reviewing academic and grey literature accessible from public sources, we present an overview of the concept and terminology of TGMZs, the approaches proposed for their delineation, and current operating examples. Additionally, we build a conceptual framework for assessing cross-border groundwater impacts by identifying their typologies and causal factors. We then apply our framework to evaluate and compare three reported methods which identify and delineate TGMZs from distinct perspectives, thereby gaining insights into their principles, performances, and limitations. Finally, we provide recommendations for further research towards optimising methods for delineating TGMZs.

The need for an integrated approach to sustainable resources management to achieve the Sustainable Development Goals has become widely recognized. Population growth, climate change, environmental degradation, and scarcity of resources have been identified as the major factors affecting society’s future. Given the fundamental societal needs for food, energy, and water, the Water–Energy–Food (WEF) nexus has emerged as a useful sustainable resource management framework and has been widely applied. However, in the Middle East and North Africa (MENA) region, there have been relatively few studies that adopt a nexus approach. In this study, the Ain Temouchent region in Algeria is used as a WEF Nexus case study. The region has a strong agricultural-based economy and the increased intensity of agricultural production in the region has resulted in the overuse of groundwater resources. Establishing a reverse osmosis desalination plant with a daily production capacity of 200,000 m³ significantly alleviated the resulting water crisis, yet its energy consumption and environmental impact raise several questions. This study identifies the critical links between the WEF sectors and using this understanding, the dynamics between them are assessed using System Dynamics Modelling. The study reveals that any further increase in agricultural production in Ain Temouchent may lead to excessive use of groundwater resources. Although desalination can help alleviate the water crisis, its high energy consumption raises concerns. The analysis shows that the use of surface water and recycled wastewater for irrigation could be possible alternatives. The study emphasizes the value of adopting a WEF nexus approach to achieve a balance between agricultural development, energy sustainability, and water resource management in the Ain Temouchent region.

This research explores the limitations and opportunities of Water Accounting Plus (WA+) for addressing water management issues in the MENA, focusing on Jordan. A comprehensive literature review and interview-based analysis were conducted to identify prevalent water management issues and evaluate information used in decision-making and strategy appraisals. The findings suggest that WA+ can enhance the spatio-temporal coverage of water resource assessments, refine estimates of irrigation water consumption, and facilitate demand management. Quantifying recharge and surface runoff requires integrating WA+ with hydrological models. Addressing climate change’s impact on future water resources requires integrating climate change projections with WA+.

Fish behaviour is one biological organisational level regularly used to assess the state of freshwater ecosystems and can be monitored using fish telemetry methods. The development of activity sensors incorporated into fish telemetered tags allows for non-spatial movement to be detected and is increasingly used to understand the energy budgets and response and fine-scale behaviour of fishes. In addition, detecting tagged fish remotely and in real time highlights the need to process fish activity data in near real time to make it relevant to managers in the water resource sector. Our study on Labeobarbus natalensis, a cyprinid, in the uMngeni River in KwaZulu-Natal, South Africa, adapted and then tested the exponentially weighted moving average (EWMA), as developed for financial predictive modelling, using activity data from fish. To determine changes in behaviour, we compared the EWMA-predicted fish behaviour against the present fish behaviour. We showed that the EWMA could adequately detect changes in behaviour on both individual and population levels. Changes in behaviour are potentially indicative of a change in environmental conditions and thus were developed into management alerts. We conducted further analyses using generalised additive mixed models (GAMM) to determine the relationship between fish activity and the environmental data collected. The GAMMs helped determine the potential drivers for changes in behaviour where the EWMA could detect these in real time. Detecting changes in behaviour in real time as a result of environmental variables can identify thresholds of potential concern influencing management decisions and allow managers to respond, contributing to improving effective freshwater management.

Water resources assessments are essential for effective planning in water-scarce regions such as Jordan. Such assessments require sufficient data in space and time. The WaPOR-based Water Accounting Plus (WA +) framework is relevant as it integrates remote sensing data and the Pixel-Based Soil Water Balance model to simulate a basin’s water balance. However, since it relies on remote sensing, this framework only tracks water consumption in irrigated agriculture and does not consider non-irrigation water use and its return flow. This paper modifies the WaPOR-based WA + framework to include non-irrigation manmade consumption and its return flows. The modified framework provides a more comprehensive water budget for the Amman-Zarqa (AZ) basin, presented in a modified WA + resource base sheet for 2018 through 2021. The results show that water availability in the AZ basin is highly responsive to precipitation changes. Average precipitation was approximately 926 Mm³/year between 2018 and 2020, corresponding to an average available water of 485 Mm³/year. However, a reduction in average precipitation by 28% in 2021 corresponded to a reduction in available water to 243 Mm³/year. Nevertheless, substantial groundwater outflows to neighbouring basins may indicate that available water is being overestimated. Manmade consumption increased by 18% from 2018 to 2021, and the total demand exceeded the available supply by 150%. This underscores the pressing need to investigate supply augmentation and conservation methods. Future studies could focus on improving the representation of groundwater dynamics in the modified framework by improving groundwater dynamics in PixSWAB and testing the modified framework with other remote sensing datasets.

There is a need to address resource security and distributional justice in developing countries. People need water, energy, and food to sustain their livelihoods, grow economies, and achieve sustainable development. The interactions between these resource sectors form the crux of water-energy-food (WEF) nexus assessments. In this study, we have utilised the WEF Nexus Index to analyse the WEF nexus of 54 African nations. The results from the analysis were used to illustrate the opportunities and constraints for future development. Generally, African countries are performing sub-optimally in the WEF Nexus Index due to the insecurity of water, energy and/or food. The performance of countries varies with context, highlighting the need for contextual analysis in identifying challenges and potential solutions. Implementation of interventions for achieving WEF security needs to be planned from an integrated perspective to optimise synergies and minimize trade-offs. Implementation of the WEF nexus approach towards simultaneous security of WEF resources has potential to improve the WEF nexus. For example and for many African countries, policies that undergird investments in energy supply projects are needed to unlock available freshwater resources and meet food requirements—energy is shown to be a critical enabler of development. Such projects can be utilised to enhance the ability of farmers to manage water through drought-proofing rainfed agriculture, an increase in irrigation development, or both. WEF nexus-based studies, policies, and projects must be focused on the direct and indirect achievement of SDGs 1, 2, 6, 7, and 13, both in terms of access and availability, to ensure distributional justice, especially in the African context. Such actions, combined with broad public participation, can have a ripple effect on other SDGs such as SDGs 5, 10, and 17, thereby reducing inequalities and building partnerships to attain these aspirational goals. The assessment of Africa’s relatively low scores in terms of the WEF Nexus Index does not represent a negative narrative. Instead, it provides an entry point to identifying hotspots and understanding the underlying challenges, through which more detailed analyses can lead to identified solutions and policies. Many African countries are trapped in an environment that could be termed a ‘poverty-unemployment-inequality nexus’ (due to the interlinkages that exist between these ‘wicked’ problems). The WEF Nexus Index provides high-level insights into these opportunities.

Sugarcane yields have steadily declined across southern Africa for the past 25 years and, despite research into the causes, there has been limited progress in addressing these trends. This study developed a methodology of assessing yield declines and performed a yield gap analysis to assess and develop recommendations to assist in combating yield declines and offering potential safeguards for the sugarcane industry against climatic extremes. Mill areas from South Africa, eSwatini, Malawi and Tanzania were selected, providing a diversity of regional hydroclimatic conditions and sugarcane agronomic management approaches. Using the AquaCrop crop model, maximum potential yields and yield gaps were simulated based on observed climate and yield data spanning 25 years. Results show that yields are declining for the mill areas in South Africa, Malawi and Tanzania, resulting in increased yield gaps, whilst yields are stagnant in eSwatini resulting in relatively fixed yield gaps. Yield gaps remained high across all six mill areas, suggesting that they remain vulnerable and exposed to climatic extremes. Modelling results suggest that these yield trends, including yield gaps, are primarily attributed to existing crop management approaches as opposed to the climatic regimes in these areas. Recommendations include several solutions that could result in an immediate response and reduce yield gaps while increasing harvestable yields. Such measures include increasing technology transfer and agronomic management education to small-scale outgrowers, adopting drought-resistant, high-yielding sugarcane varieties, contouring and mulching, improving soil structural properties and minimizing in-field traffic. The study concludes that if sugarcane growers are to withstand the effects of extreme climatic events, they have to consider shifting crop management approaches and be proactively included in related research.

The intricate connections between water, land, food, energy, and climate change require a multicentric approach to evaluating the trade-offs and synergies needed to achieve sustainable development. For example, the amount of water required in irrigated agriculture, consumptive water uses, and hydro-power production can potentially lead to water pollution, and negatively affect hydrological regimes. However, Operationalizing Water Energy Food (WEF)-nexus thinking has evolved such that a division between researchers (e.g., academia), political actors (e.g., policymakers), and development partners (e.g., promoters) has formed. This lack of connection can lead to a situation where there is incoherent governance of WEF resources management. In the Southern African Development Community (SADC) context, the WEF nexus approach is at the core of regional sustainable development plans and strategies. This paper analyses the ambitions and the expected outcomes of the Songwe River Basin Development Programme (SRBDP) and reflects on how governance coherence of WEF resources rooted at the grassroots level contributes toward achieving “nexus-doing”. The SRBDP exhibits a multi-stakeholder connection of interests geared towards a common target (i.e. stabilisation of the River Songwe flow). The SRBDP creates a multi-centric action system within the water, energy, food, and climate change adaptation role-players to achieve this overarching goal. The connections espoused in this system form the basis for nexus-doing in the Songwe River Basin. The major findings are: (i) there is a significant infrastructural demand in the Southern Africa Development Community (SADC), anchored in the development of water, land, food, and energy resources; (ii) governance coherence in the SADC context can be identified at both vertical and horizontal levels; (iii) the nature of trade-offs and synergies exhibited in SRBDP is valuable for making progress towards the operationalization of integrated WEF-nexus resource management; (iv) governance inconsistencies/ambiguities are better diagnosed and addressed in implementing nexus-doing initiatives such as SRBDP. Based on the findings, the following recommendations are proposed: (i) build upon small wins and support snow-balling successes to upscale promising initiatives-for instance the joint agreement by Tanzanian and Malawian governments to stabilize Songwe River flow by inaugurating the joint cooperation and equitable sharing of the Songwe watercourses (AFDB, 2019); (ii) invest in capacity building and human resources for the Songwe River Basin Commission and associated stakeholders to become more effective;-for posterity of sustainable developments in the Songwe River Basin; both the Tanzanian and Malawian governments in partnership with development partners need to upscale the investment in human capacity development and resource capacity development of the Songwe River Basin Commission (SRBC) as the joint development vehicle for the basin. and (iii) enrich policy assessment tools tailor-made for SADC. This tool will help in policy accounting to help minimize duplication, and ambiguities by fostering cooperation and policy mapping across the WEF-nexus sectors in the SADC region. This work can guide approaches to close the gap between nexus-thinking, and nexus-doing, something that is increasingly called for.

Water-Energy-Food Nexus Narratives and Resource Securities: A Global South Perspective provides a knowledge synthesis on the water-energy-food (WEF) nexus, focusing primarily on the global south. By presenting concepts, analytical tools, and case studies, the book serves as a practical resource for researchers, policymakers, and practitioners in sustainability and functional roles across all three sectors. It addresses key issues related to data availability, tools, indices, metrics, and application across multiple scales, beginning with a summary of existing knowledge. Finally, it examines the WEF nexus, presents global insights, and discusses future considerations and implications. This book presents an overview of existing knowledge on the WEF nexus and examines how such research aligns with emerging global WEF nexus perspectives, making it ideal for professionals, government entities, private industry, and the general public.

Evapotranspiration (ET), a key variable in both water and energy cycles. It is very challenging to measure or estimate in large regions. Among many approaches to estimate ET indirectly (e.g. through hydrological modelling), models that are based on satellite remote sensing data (RS) are increasingly being used. However, the RS-based models inherit uncertainty from many sources, such as the model’s algorithm and parameters, input satellite data, and processing techniques. It is challenging to assess this uncertainty due to limitations of validation data, high volume and high dimensionality of RS data. Many studies have evaluated uncertainty in RS-based estimation of ET using different methods and reference data. The suitability of methods and reference data subsequently affect the validity of these evaluations. Therefore, it is necessary to have an overview of different evaluation methods and their uses. This study aimed to systematically review original research papers that assessed uncertainty or accuracy of RS-ET model or data products. We categorized these papers and quantified based on (i) spatial and temporal scale of ET estimation, (ii) types of uncertainty, and (iii) methods used to assess uncertainty. Studies have been geographically concentrated in North Asia, North America, and Europe. Most studies used the validation method, which quantifies the discrepancy between pixel-based ET estimation with an in-situ estimation. Although a standardized validation approach for satellite-based ET estimates is not yet ready, most validation studies employed Eddy Covariance (EC) flux towers for reference estimation at field-scale. In regions where in-situ measurements are limited, many studies use the residual of the water balance as reference. However, few studies considered uncertainty in the reference estimation and mismatch of spatial and temporal scales. For monitoring agricultural fields, most RS-ET methods have been reported with high accuracy. When applying these methods to larger extent, additional assessments are required to better inform data users of the quality of RS-ET estimation. These include cross-validation, sensitivity, and uncertainty analyses. Overall, this review showed the progress in evapotranspiration estimation using satellite data in terms of uncertainty assessment.