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.

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.

Problems manifested within social-ecological systems (SES) exhibit dynamic complexity and hold implications for current and future human well-being and environmental sustainability. The complexity of these issues, the ever-present uncertainty inherent to SES, and the multi-stakeholder settings in which they are discussed call for participatory modelling to support decision-making on socio-environmental issues. Yet, this challenging endeavour requires a structured approach — a modelling cycle — to facilitate engagement with the implications of participation and uncertainty as focal points for Good Modelling Practice (GMP). Here we propose an integrated policy analysis framework for SES modelling using System Dynamics (SD). This framework stems from integrating two existing modelling cycles that individually consider participation and uncertainty in SD modelling. Three global modelling phases and a set of tools to address the participation and uncertainty features in SES modelling are distinguished. The framework contributes to mainstreaming GMP, offering a structured model-based approach to enhance the robustness and social acceptance of policies on critical socio-environmental issues.

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.

The social-ecological systems (SES) approach elicits a broad understanding of some of the most pressing socionatural challenges (e.g. resource scarcity, biodiversity loss, and climate change) and the responsibility that humans have in addressing them. System dynamics has proven a powerful paradigm for dealing with complex SES-related issues. Here we discuss some ethical considerations of using system dynamics (SD) to model SES, something that is often either overlooked or discussed as an isolated issue. Sustainable development and human rights are used as ethical standpoints across the modelling cycle, opening the discussion around guiding principles that need to be considered when modelling SES. Based on these, a set of guiding ethical questions are identified and classified across a participatory SD modelling cycle. This structured approach is a simple yet potentially useful tool for SD practitioners to examine the ethical implications of their modelling endeavours in the context of grand societal challenges.

Water enables health, education, and economic well-being opportunities for humanity. Access to basic water and sanitation services, freshwater variability, and water storage are some of the dimensions that may impact on human development worldwide. Yet few studies quantitatively explore the relationship between water and human development. This study uses a statistical approach to quantify the Water-Human Development relation in a global sample, both in terms of correlation and causality between variables. Correlation is established using a multiple linear regression approach, while causality is explored by implementing the multi-spatial convergent cross mapping technique. Our study finds strong interdependence between water-related variables and human development globally. Access to water services positively influences the Human Development Index (HDI), seasonal variability of freshwater resources restricts it, and large water storage is not significant. The analysis is robust between 2000 and 2017, and implies that a 1% increment in a country's HDI is associated with a 1.3%–3.2% increment in water and sanitation access. Causal analyses show strong coupling, suggesting positive feedback between access to water services and HDI that could be exploited. Reaching Sustainable Development Goal 6 requires closing the water and sanitation access gaps while addressing freshwater variability challenges. This will result in global human development benefits.

Over the past decade, the water, energy, and food (WEF) nexus approach has evolved to become a focus of the Southern African Development Community (SADC) development strategies. However, a lack of empirical evidence, appropriate methods, and qualitative and quantitative tools to implement the WEF nexus approach has been highlighted. This chapter describes the application of the WEF nexus approach in the Songwe River Basin (SRB) located on the border between Malawi and Tanzania as a demonstration of how this lack of evidence and tools is starting to be addressed. The basin is currently facing rapid population growth, which is leading to a considerable increase in resource demand and environmental issues and has been identified as a priority basin for SADC. The SRB Development Programme (SRBDP) includes several projects that collectively aim to improve the environmental and socioeconomic status of the basin. The integrated approach proposed to assess the SRBDP's expected outcomes through a WEF nexus lens is based on the development and application of qualitative and quantitative tools that support decision-makers to assess feasible sustainable development pathways in the basin, and more broadly in the SADC region. This chapter focuses on the qualitative analysis of the WEF nexus system and explains the process of identifying the major sectors and subsectors involved in the SRBDP, the main interlinkages between them, and potential synergies and trade-offs assessing how decisions made in a sector may influence others. The qualitative analysis of the SRB shows that although the projects included in the SRBDP are expected to have positive impacts on the environment and the socioeconomic system of the basin, downsides that may have an impact on human and ecosystem health are also possible. Early identification of such issues can help to limit detrimental impacts in the future. In the analysis, potential Sustainable Development Goals (SDGs), objectives, and indicators that may be addressed in the SRB are identified, highlighting the importance of applying the holistic approach to enhance and boost the achievement of SDGs in the basin.

The water-energy-food (WEF) nexus is shown to be a highly interconnected, complex system, operating over multiple time scales, and at spatial scales from household to global. The key WEF nexus foci issues and challenges are known to be extremely diverse and change depending on the local situation and setting, the scale at which the nexus is analyzed, and even according to the sector used as the nexus entry point. As such, there are a multitude of approaches and methodologies for studying, assessing, and analyzing the nexus, which can be adopted to suit the specific case under investigation. There is no “silver bullet” modeling or methodological approach to studying the nexus. Some common and regularly employed nexus investigation approaches are outlined in this chapter, ranging from purely qualitative conceptual systems mapping aiming at getting a high-level understanding of nexus connections for a given study area, through to quantitative approaches including system dynamics modeling, agent-based modeling, life cycle assessment, and (multiregion) input-output modeling. Each approach has strengths and limitations, explored here, and the selected tool should address the research questions being considered as well as the goals of the study. In addition to tools and models, results need to be translated into “real-world” practicalities to have a better chance of being taken up and adopted. To this end, this chapter also introduces some indices and metrics that are often applied to communicate nexus results and messages to policymakers in a nontechnical language. This effort hopes to better disseminate and communicate the idea of integrated nexus thinking, especially in a policy- and decision-making domain.

Water, energy, and food (WEF) systems form a complex interconnected network, operational at scales from the household up to the global. These scales, like the nexus sectors themselves, and mutually interconnected, with lower-level characteristics help drive higher-level resource management, and vice versa. This chapter highlights recent WEF nexus research at spatial scales from household, to national, and up to global. The studies demonstrate the vast diversity in nexus issues and challenges, along with a concomitant diversity of research and assessment approaches to tackling and better understanding these issues. This chapter closes with a discussion on interactions between the scales, and how policy developed at one scale may impact on other scales, potentially in unanticipated and detriment ways. The investigation into cross-spatial scalar nexus interactions is in its infancy and represents a promising avenue for future research effort. Another aspect not covered so far by research is the issue of differences in the temporal scale in the nexus, both in terms of policy setting and implementation and in terms of impacts to people. This chapter represents another major topic for future research to better guide, develop, and understand the impact of policy and climate change on nexus resources and livelihoods, and vice versa.

Agriculture is a major consumptive user of water through evapotranspiration (ET). Quantification of actual ET (ET_a) is of significant interest to better address water management and improve decision making in the agricultural sector. Many methods to estimate ET are available. However, due to the increasing need of validation of estimates of ET from various techniques, there arises a call for a critical comparison of ET_a estimated from a combination of methods. This research presents a critical comparison of ET_a estimates obtained using ground based (eddy covariance), remotely sensed (ET ensemble), and simulated data (a crop-soil-water balance model, SIMETAW#). The study focuses on experimental sites in Nebraska, Oklahoma and California (USA). Results show a relatively small and consistent variation between the three methods. The results are relatively close giving a reasonable impression of the expected ET_a at a site including variability which is useful to address agricultural practices. The estimates from remote sensing deviate from the other two methods since the method used is relatively new and requires further research to improve measurements and ET estimation. This study offers water managers at the sites new information for reliable, multi-source ET estimation for water resources planning and the study is in principle replicable at different locations.

Globally, freshwater resources are threatened, resulting in challenges for urban water supply and management. Climate change, population growth, and urbanization have only exacerbated this crisis. For the Caribbean, climate change through the impact of increasing temperatures and rainfall variability has resulted in more frequent and intense episodes of disasters including droughts and floods which have impaired the quantity and quality of freshwater supplies. Using Caribbean-specific climate forecasting, it is shown that rainfall totals in Kingston, Jamaica, are expected to reduce by 2030 and 2050 under two RCPs. In addition, the timing of the primary rainy season is expected to shift, potentially impacting water supply security. Analysis of the potential of rainwater harvesting (RWH) to augment supply and enhance water supply resilience shows that in two communities studied in Kingston, it can contribute up to 7% of total water supply. Household storage requirements are about 1 m³ per household, which is feasible. RWH offers the potential to contribute to climate change adaptation and mitigation measures at a household level. Policy, incentives, and increased awareness about the potential of RWH to meet non-potable household demand in Kingston must be improved, as well as efforts to reduce the currently unreasonably high levels of non-revenue water in order to move towards an integrated, sustainable, and climate-resilient urban water supply strategy for the city.