Keywords

1 Introduction

In a landmark report on global risks, the World Economic Forum (WEF 2011) highlighted the need for a synergistic, convergent understanding of the food-energy-water nexus by emphasizing that a rapidly rising global population and growing prosperity are putting unsustainable pressures on resources, and that any strategy that focuses on one part of the food-energy-water nexus without considering interconnections risks serious unintended consequences. The interconnections and couplings in food, energy, and water systems have been recognized in recent literature (Bazilian et al. 2011; Hoff 2011; ICIMOD 2012; Endo et al. 2015; Scott et al. 2015). However, computational modelling that reflects those convergent and divergent interconnections and can inform policy development and risk management requires far more research and resource investments (Bizikova et al. 2013; Howells et al. 2013; Biggs et al. 2015; Zhang and Vesselinov 2017). In addition to human population growth and income disparity, the degradation in ecosystem services also poses a monumental risk at the nexus of food energy and water systems (Hoff 2011; Rasul and Sharma 2016).

In the face of these exogenous and endogenous drivers of change in the nexus, the central role of the changing risk from extreme hydro-meteorological events, such as extreme temperature and rainfall variability, poses a fundamental scientific and policy challenge for managing risk. Poor understanding of biogeochemical, landscape and policy responses to “primary” extreme events typically leads to “consequent” extreme events such as floods, droughts, wildfires, and water contamination events, which in turn pose monumental challenges for secure provision of food, energy, and water in the affected regions. The “antecedent” conditions in a landscape, e.g., soil moisture content, riparian buffers, and tree density, can play a critical role in mitigating the effects of primary extreme events and the emergence of “consequent” natural hazards and disasters such as widespread floods, droughts, and wildfires (Field et al. 2012). Further, there is an active community of research investigating the attribution of global climate change to the shifting trends in the frequencies, intensities, and durations of “primary” extreme events (e.g., see NAS 2014). There is widespread consensus in the scientific community that global climate change will very likely change the frequency, intensity, and duration of two primary extreme events (temperature and rainfall variability) from watershed to basin to regional scales under different Greenhouse Gas (GHG) forcing scenarios (Field et al. 2012). However, there is considerable uncertainty surrounding the projection of the changing frequencies and intensities of these events at multiple scales (e.g., see Yang et al. 2016a; Zia et al. 2016). Large uncertainty about changes in extreme events hinders local- to regional-scale efforts to incorporate the risk from extreme events in the decision-making processes of critical actors engaged in the production and consumption of food, energy, and water.

Broadly, the first generation Early Warning Systems (EWS) with varying levels of forecast accuracy have been deployed for a variety of natural hazards including sudden-onset events such as earthquakes, tsunamis (Taubenböck et al. 2009; Liu et al. 2007; Thomalla and Larsen 2010; Spahn et al. 2010), landslides (Intrieri et al. 2012), and flooding from rivers and tsunamis (Basher 2006; Thieler et al. 2009), as well as more gradual processes like drought (Pozzi et al. 2013; Pulwarty and Sivakumar 2014) and malaria transmission that result from climate variability (Thomson et al. 2006). As such, EWS are established to mitigate hazards and can act on a multitude of temporal and spatial scales. The temporal scales (early warning lead times) range from minutes in the case of earthquake and tsunamis, to hours in the event of river flooding, and at times months and even years in the case of drought. Food, energy, water security early warning systems must encompass lead times from hours to decades and perhaps even centuries in the face of global climate change. Short- to medium-term lead time forecasts can be used by policy makers, managers, and citizens for both operational and tactical decision making for adapting to the risk of extreme events, while long term lead time forecasts are generally usable for strategic decision making (Zia and Hammond Wagner 2015) and increasingly critical for building resilient and sustainable planetary systems (Zia 2021). Effective communication of uncertainty embedded in Nexus-EWS and improved understanding of synergies and trade-offs in the nexus due to differential sources, processes, and output of a social ecological system were enunciated as desirable goals in a UNFCCC COP24 side-event focused on mainstreaming Nexus-EWS for adaptation to climate change (Zia 2018).

The goal of designing convergent technologies, such as Nexus-EWS, is thus driven by critical global environmental policy need to adapt to increasing frequency and intensity of extreme events differentially distributed across the planet (e.g., see IPCC 2021). Deployment and continual improvement of such convergent technologies may enhance stakeholder understanding of nexus interactions, couplings, and processes, which in turn are critically needed for forecasting and managing the social ecological risk accentuated by climate change-induced extreme events (e.g., see Howarth and Monasterolo 2016). This approach hypothesizes that convergent risk management interventions through Nexus-EWS reduces risk from extreme events and builds resilience against internal and external extreme events by increasing food, energy, and water security across different eco-hydrological regions. A central hypothesis is that Nexus-EWS could be harnessed as convergent resilience technologies that can project, under different climate change, socio-economic, and land-use scenarios, the shifting risk from extreme events on safe and secure provision of food, energy, and water for the affected populations at national and regional scales, including but not limited to communities in the Central and South Asia. Ultimately, the promise of a Nexus-EWS as a convergent technology is to facilitate both the private and public decision making by enabling transparent understanding of synergies and trade-offs embedded in managing complex interactions of the nexus.

Widespread deployment of convergent Nexus-EWS have strong potential to build resilience against extreme events and improve adaptive capacity of vulnerable human and ecological populations exposed to extreme events. While different conceptual notions of vulnerability and resilience have been explored in multiple disciplines (e.g., ecology, political ecology, human ecology, disaster management, climatic impacts, human dimensions of global change) and theories (e.g., pressure and release), which have been reviewed by Liverman (1990), Dow (1992), Ribot et al. (1996), Eakin and Luers (2006), Pelling (2003), Füssel and Klein (2006), Adger (2006), Cutter (2003), Ionescu et al. (2009), and Janssen et al. (2006), this chapter considers vulnerability and resilience as properties of a coupled natural and human system, as elaborated by Turner et al. (2003a, b) in the context of a social-ecological system. Previously, the system-level frameworks for vulnerability and resilience have been applied in a range of empirical assessments (Luers et al. 2003; O’Brien et al. 2004; Schröter et al., 2005; Ionescu et al. 2009). Despite the promising conceptual developments about the system-level notions of vulnerability and resilience in sustainability science and social ecological systems community, there are significant challenges in assessing vulnerability and resilience of coupled natural and human systems (e.g., see Adger 2006; Luers et al. 2003; Luers 2005). In the long run, the proposed approach of designing, deploying, and iteratively evaluating the performance of convergent technologies, such as Nexus-EWS, presents a monumental opportunity with increasingly widespread availability of open-sourced socio-environmental data and advancements in artificial intelligence (AI), yet there are many scientific and technological challenges, as well as ethical and geopolitical governance challenges that impede the realization of Nexus-EWS.

Section 5.2 of this chapter presents a brief review and discussion of Nexus-EWS as convergent technologies. Section 5.3 provides promising examples of Nexus-EWS applications with specific focus on Central and South Asian countries, both within countries and across regional scale entities. The scientific and technical challenges for deploying, sustaining, and improving Nexus-EWS to generate accurate early warnings about the risks to secure and safe provision of food, energy, and water and identify early action capabilities are discussed in Sect. 5.4. The growing role of open-sourced big data, such as remotely sensed satellite data and AI, and their intersection with traditional security dimensions are explored in Sect. 5.5. Geopolitical and ethical issues arising from the deployment of convergent technologies such as Nexus-EWS are presented in the concluding Sect. 5.6.

2 Nexus-EWS as Convergent Technologies

In this chapter, we follow Pahl-Wostl (2019) definition to characterize convergent understanding of the nexus: “Addressing security from the perspective of the Water-Energy-Food nexus refers to reducing trade-offs to acceptable levels and to enhancing synergies between efforts to simultaneously increase water, energy, and food security, respectively, to sustain human-wellbeing, economic production and environmental integrity and to enhance the resilience of the human-environment-technology system as a whole (Pahl-Wostl 2019: 361).” In the face of multiple, yet highly uncertain exogenous and endogenous drivers of change in the nexus, the changing risk from primary and secondary extreme events plays a central role and poses a fundamental scientific and policy challenge for building climate resilience. Poor understanding of biogeochemical, landscape, policy, and behavioral responses to “primary” extreme events may lead to “consequent” extreme events such as floods, droughts, and water contamination events, which in turn pose monumental challenges for secure and safe provision of food, energy, and water in the affected regions, as shown in Fig. 5.1.

Fig. 5.1
A flow diagram in 4 stages. Global climate change, frequency and intensity of floods, droughts, and heatwaves along with rapid urbanization and poverty, water security, and food and energy security. The arrows have plus and minus symbols that represent direct or inverse proportionality. The hypothesized intervention effects are included.

A conceptual overview of the hypothesized intervention effects induced by convergent technologies such as Nexus-EWS, Ecological Design & Ecosystem Conservation in promoting food, energy, and water security

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The food, energy, and water early warning systems (Nexus-EWS) approach is embedded in social ecological systems theory (Gunderson 2001; Ostrom 2009) and complex adaptive systems theory (Holland 1992) that explicitly models the interconnections and dynamics of various nexus components and drivers of change across consistently defined eco-hydrological regions. In this tradition, many climate risk assessments and nexus studies have highlighted the need to develop regional/river basin scale social ecological systems models for improved understanding and the management of risk posed by both endogenous and exogenous drivers of change (NAS 2014, 2016). Complexity science-informed research has demonstrated that when exposed to exogenous shocks (e.g., climate change-induced extreme events) or endogenous surprises (e.g., ecological collapse or a geopolitical conflict), social ecological systems do not necessarily go through gradual change, but rather critical transitions (tipping points and thresholds) may abruptly change the trajectory of state variables (e.g., Scheffer 2010). It is hypothesized that a loss of resilience can trigger critical transitions that induce the state variables in the system to be abruptly tipped into a different state (Carpenter et al. 2005; Folke 2006; Holling 1973). In the context of the social ecological systems approach to design convergent technologies for building resilience against the extreme events, resilience refers precisely to the magnitude of disturbance that can be absorbed before a system changes to a radically different state, as well as the capacity to self-organize and the capacity for adaptation to emerging circumstances (e.g., Carpenter et al. 2001; Folke 2006; Berkes et al. 2008).

However, many resilience and vulnerability assessments of the nexus to the extreme events, lack a critical dimension that concerns the control and adaptive management of complex adaptive systems, such as river basin social ecological systems (Zia 2021). Inadequate understanding of non-linear processes and threshold effects pose fundamental challenges in distinguishing controllable from non-controllable processes in social ecological systems (Zia et al. 2022b). In particular, the controllability in the decision-making processes at micro-scale levels, such as households and firms (farmers, utilities, etc.), is poorly understood. It is recognized in the complexity science literature that the properties of complex adaptive systems, such as emergence, adaptation, and self-organization of heterogeneously interacting components, do not necessarily lend to top-down control and dynamic optimization (e.g., see Holland 1992; Levin 1998). Tipping points, thresholds, non-linearities, and irreversibilities in ecological and biogeochemical systems need to be adequately accounted for to effectively model social ecological resilience and vulnerability to extreme events. Similarly, tipping points in social systems induced by poor governance and infrastructure planning may lead to maladaptation and vicious social traps. Conventional engineering economic models of system optimization and top-down control do not necessarily work in managing the risk and trade-offs in multi-scale social ecological systems beset with thresholds and tipping points (e.g., Zia et al. 2011, 2014; Blair and Buytaert 2016; Chaffin et al. 2016). Polycentric governance systems balance bottom-up and top-down (multi-level) and lateral (inter-sectoral) pathways of influence (Ostrom 2010; Pahl-Wostl et al. 2012; Pahl-Wostl and Knieper 2014). They are assumed to have high performance with respect to integration across issues and scales and regarding adaptive capacity (Ostrom 2010; Folke 2006; Pahl-Wostl et al. 2012; Pahl-Wostl 2009; Blomquist and Schlager 2005).

In the nexus domain, potentially increasing frequencies and intensities of extreme events are likely to increase socio-political and ecological stresses with growing demand for food, energy, and water. Novel, bottom-up approaches to model the interconnections and control in the nexus are needed for generating transformative and actionable science (e.g., Liu et al. 2015). Such bottom-up computational approaches may provide novel contrast to top-down, constrained linear programming approaches for assessing resilience and control in the nexus. Zhang and Vesselinov (2017) developed a Water Energy Food Security Optimization model, an example of a top-down approach, that minimizes cost of energy supply, water supply, electricity generation, food production, and CO2 mitigation for a given socio-economic demand in a stipulated timeframe. Similarly, Karabulut et al. (2016) used the Soil and Water Assessment Tool integrated with a variety of food and energy indicators, to assess water scarcity scenarios in the Danube sub-basins. Damerau et al. (2016) present a globally scaled, top-down optimization model of five regions to investigate the global water demand under three future food preference scenarios and two scenarios of future resource preferences for electricity and transport fuels. These top-down, integrated assessment approaches assume global control of societal preferences for food, energy, and water demand and typically specify convenient objective and constraining functions to identify optimal pathways for minimizing risk from extreme events.

While top-down approaches provide useful baselines to explore the nexus interactions and couplings, bottom-up approaches informed by social ecological systems theory have the potential to generate actionable convergent technologies for managing risk at spatially distributed scales that account for non-linear interactions of social, ecological, and technological components in complex adaptive systems. Bottom-up, computational modelling of resilience and control in the nexus has the potential to generate novel, interdisciplinary insights for managing the risks posed by multi-scale drivers of change, ranging from global-scale, climatic shifts to local-scale, land-use and land-cover changes induced by demographic and socio-economic shifts. In particular, the landscape design, which requires a bottom-up modelling, can play a critical role in differentiating resilient from non-resilient scenarios in the nexus, particularly in the face of changing frequency, intensity, and duration of extreme events. A global controller cannot necessarily predict or steer a landscape in an optimal direction in the face of large uncertainty about potential risks from endogenous and exogenous drivers of change, yet a well-defined objective function is typically assumed in constrained, linear programming approaches to assess resilience in the nexus. In fact, the locus of control in deciding the evolution of landscape typically rests with the decision-making and learning processes of landowners/land users, whether they are homeowners, farmers, businesses/firms, or local towns, both in response to and in anticipation of extreme events. Higher-level governance entities may develop land planning guidelines and rule structures, induce or coerce decision-making processes at household and firm levels, but the implementation of these rules and inducements typically takes place at the local, distributed scales of households and firms. Box 5.1 shows the positive social impacts that can be derived from nature-based solutions and ecological design approaches to reduce the risk from extreme events from increasing urbanization and build resilience in the nexus. Similar resilience enhancing benefits derived from the potential Nexus-EWS applications are presented in Sect. 5.2.

Box 5.1 Emerging role of nature-based solutions and ecological design approaches in reducing the risk from extreme events in the nexus

The recent nexus research has highlighted the need for future research to assess the differences between “business as usual” urbanization scenarios versus natural infrastructure landscape design scenarios in terms of their ability to modulate and buffer the impacts of extreme events. In the business-as-usual urbanization scenario, the growth and decline of cities can be modeled with urbanization models, such as UrbanSIM (Waddell 2002), and complexity science tools, such as cellular automata and agent-based models (e.g., see Batty 2007). Urbanization typically results in decimation of lower-valued forest lands, wetlands, riparian buffers, and even agricultural lands near urban lands (Grimm et al. 2000, 2008). In contrast, in a natural infrastructure landscape design, nature-based solutions for food and energy production and conservation of water are explicitly designed and implemented on the landscapes (Mitsch 1992; Lyle 1999; Makhzoumi and Pungetti 2003). Such nature-based solutions may include: agro-ecological practices for food production, wetland and riparian buffer conservation for flood mitigation, rooftop gardens and vertical gardens in urban areas, micro-hydro power generation projects, biomass and biowaste projects that “complete the loop” from waste to source, cover crops and conservation tillage in the face of drought, and constructed wetlands and ponds for slowing down nutrient run off (Makhzoumi and Pungetti 2003; Steiner 2014; Van der Ryn and Cowan 2013).

3 Applications of FEWS-EWS

The operational and tactical scale deployments of Nexus-EWS will likely take place in a few decades, or perhaps a few years henceforth, the strategic scale development of Nexus-EWS has recently seen an uptick in research and development (R&D) investments. Two specific initiatives are highlighted here: (1) Under the World Bank funding, a top-down hydro-economic modelling approach was used to ascertain the synergies and trade-offs induced by water, energy, and food management decisions on the future of nexus security under alternate climate change scenarios in the Indus (Yang et al. 2016a) and Brahmaputra (Yang et al. 2016b). (2) Under the funding from the US State Department’s Fulbright Commission, I am working with a Transboundary Water-In Cooperation Network (TWIN) to develop a bottom-up Integrated Regime Shift Assessment Model to build tactical and strategic Nexus-EWS capacity for anticipating the impact of hydro-climate regime shifts on food, energy, and water security and designing multi-governance mechanisms for building resilience in transboundary Indus, Jordan, Mekong, and Amazon basins. Both the application approaches highlighted in this section are extendable to all the regions of the world, including Central and South Asia.

3.1 Hydro-Economic Approach

Yang et al. (2016a) evaluates the nexus in the Indus River of Pakistan using a hydro-agro-economic model extended with an agricultural energy use module. Impacts of a range of climate change scenarios on the nexus in the Indus Basin were modeled and then the potential of different alternative water allocation mechanisms and water infrastructure developments to address growing water, energy, and food security concerns in the country were assessed. Results show growing water and energy use under hotter and wetter climate conditions (Fig. 5.2). While more flexible surface water allocation policies can mitigate negative climate change impacts on agricultural water and energy use allowing for larger crop and hydropower production, such policies might also increase the inter-annual variability of resource use. Moreover, a more flexible surface water allocation policy would increase surface water use in the basin, while groundwater and energy use would be lower (Fig. 5.2). This project recommended that integration of a groundwater model and an energy market model was needed to further refine the longterm nexus projections under alternate climate scenarios. Explicitly addressing changes in food and energy demand as a result of demographic dynamics are also needed in future extensions of this model.

Fig. 5.2
A column graph for temperature, precipitation, system, allocation, sugarcane, wheat, and hydropower. The nodes in system and allocation are labels, while others are numbers. Each node is interconnected with the nodes in adjacent columns.

Source Yang et al. (2016a)*

Indus basin annual crop and hydropower production under the impacts of climate change (first two axes), dam development (third axis), and alternative water allocation scenarios (fourth axis). Green lines represent scenarios that satisfy thresholds and red lines represent scenarios that cannot satisfy threshold. In this figure, scenarios that result in sugarcane production, wheat production, and hydropower generation all below historical condition are labeled as red lines.

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Using similar hydro-economic approach, Yang et al. (2016b) explores transboundary management implications of water diversions by upstream Chinese and Indian riparian partners on the downstream Bangladeshi regions of Brahmaputra basin. Development of new hydropower projects, upstream water diversions, and possible climate changes have introduced concerns among riparian countries about future water supply for energy and food production in this basin. Yang et al. (2016b) present details of this calibrated hydro-economic water system model of the Brahmaputra basin that is coupled with ex-post scenario analysis under the “nexus thinking” concept to identify and illustrate where development paths are in conflict. Results indicate that the ability of future development to remain free of conflict hinges mostly on the amount of precipitation falling in the basin in the future. Uncertain future precipitation along with uncertain future temperature and the unknown amount of upstream water diversion combine to strongly influence future water, energy, and food production in the basin. Specifically, decreases in precipitation coupled with large upstream diversions (e.g., diversion in the territory of China) would leave downstream Bangladesh unable to secure enough water to produce their desired energy and food (Fig. 5.3).

Fig. 5.3
A column graph for temperature, precipitation, China Diversions, India Diversions, F A A and rice. The nodes are numbered and interconnected with the nodes in adjacent columns using 2 different colored lines. Multiple to and fro lines for scenarios outside of thresholds are clustered in the column F A A. Multiple to and fro lines for scenarios within thresholds are clustered between 0 and 20000 in the column F A A. Values are approximated.

Source Yang et al. (2016b)*

Nexus modelling in Brahmaputra basin. Flood affected area (FAA) and rice production in Bangladesh under the impacts of climate change and upstream diversions. Blue lines represent scenarios within thresholds and pink lines represent scenarios outside of thresholds. Precipitation change and Chinese diversion cause tradeoff between FAA and rice production in Bangladesh. While positive precipitation change benefit rice production, it results in more FAA.

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3.2 Integrated Regime Shift Assessment Modelling (IRSAM) Approach

Coarse resolution climate impact assessments in the upper Indus basin suggest the likelihood of radical shifts in its eco-hydrological regime initiating a cascade of downstream impacts on its nexus (Immerzeel et al. 2010; Rasul 2014). More accurate projections at finer space-time resolution are direly needed for proactive policy and planning interventions to mitigate impending flood and drought risks. More accuracy requires the development of calibrated eco-hydrological models at the basin scale, and their integration with socio-economic models to estimate the risk posed by climate change-induced extreme events and to help identify leverage points for policy makers and planners to identify strategic interventions that account for couplings and critical transitions. Previous research discussed in Zia and Glantz (2012), Zia (2013), Zia and Hammond Wagner (2015), Ali and Zia (2017), and Zia et al. (2022a) suggest that uncertainties about monsoon variability and glacial melt timing pose daunting infrastructure design planning and nexus challenges. In the upper Indus basin, the melting of glaciers in the Tibetan delta is expected to result in significantly decreased water availability (e.g., see Immerzeel et al. 2010).

After simulating mean upper Indus discharge for the baseline (2000–2007) and future climate for A1B SRES scenario (2046–2065), Immerzeel et al. (2010) projected a mean 8.4% decrease in the upper Indus water supply for this mid-century scenario. Upstream water supply is crucial to sustaining water storage capacity in Tarbela dam, which in turn regulates the largest irrigation network in the downstream Indus. High-resolution models are needed to understand different glacial melt scenarios and shifts in the Monsoon to better predict long-term water supply issues in the Indus basin beyond mid-century scenarios (Ali and Zia 2017). Hanif et al. (2013), using the Pakistan Meteorological Department (PMD) dataset has found significant shifts in Monsoon direction from Gilgit-Hunza basins in the upper Indus towards the Hindukush mountains. By relating changes in upstream water availability to net irrigation requirements, observed crop yields, caloric values of the crops, and required human energy consumption, Immerzeel et al. (2010) estimated that 26.3 ± 3.0 million fewer people in the Indus basin will be fed. There is however a lot of uncertainty embedded in these projections, and Immerzeel et al. (2010, Fig. S3) found that the model projections are sensitive to glacial melt timing, while monsoon shifts were not incorporated in these projections. Further, the impacts of extreme events, such as the mega-floods of 2010 in the Indus basin, on food and energy production were ignored as well. Reduced water quantity in the upper Indus will also affect the ability of hydropower dams to operate at their maximum capacity, especially during winter months. Another serious concern arises due to the flood induced massive movement of sediments in the upper Indus that may shorten the lifespan of three critical dams (Tarbela, Diamir-Bhasha, and Bunji), consequently adversely affecting the energy security situation in Pakistan.

Lack of information on modelling feedback within and between social and ecological systems has hampered policy makers’ and watershed managers’ capacity to use the outputs of simulation models to develop effective adaptive management responses (Ostrom 2010). This approach builds upon Filatova (2015) proposed integrated approach by combining multiple modelling approaches—statistical analysis, system dynamics, equilibrium models, and agent-based models, which are typically used for detecting regime shifts in social ecological systems. Integrated modelling approaches can account for cascading interactions between coupled human and natural systems in the form of two-way feedback loops in the simulation models (e.g., see Ecology and Society special issue, Hull et al. 2015). Utilizing such an integrated model would potentially allow for tracing cascading effects when crossing a threshold in a subsystem, or the social ecological system may affect another threshold in the other subsystem, or emergence of the moving thresholds.

The integrated regime shift assessment modelling (IRSAM) (Fig. 5.4) will integrate a hydrological model, e.g., SWAT with an Agent Based Model (ABM) to simulate endogenous dynamics of (1) water, energy, and food availability and socio-economic stability in the entire river basin under alternate interacting regime shifts induced by global climate change and El Nino Southern Oscillation (ENSO) at global scales, (2) transboundary governance at basin scales and reactive versus anticipatory water, energy, and food policy regimes at national and subnational scales (Fig. 5.4). The IRSAM will have the ability to simulate the emergence of socio-economic stability regimes (e.g., mass migrations or not, conflict or cooperation) under different anticipatory and reactive scenarios co-designed with stakeholders in focal riparian countries spanning Indus and other focal river basins in this project. The computational workflow of the IRSAM described in Fig. 5.4 will be implemented in a workflow management system such as the Pegasus Workflow Management System, similar to Zia et al. (2016, 2022b) for transboundary Missisquoi river in the Lake Champlain basin.

Fig. 5.4
A block diagram. 2 interrelated blocks of downscaled regional or global climate model and E N S O forecast model leads to another 2 interrelated blocks of Glacial Melt model and Basin wide hydrological model S W A T respectively. Block for basin wide hydrological model leads to land use land cover and D E M and a block of Agent Based Model which contains interrelated blocks.

Computational structure of a bottom-up Integrated Regime Shift Assessment Model (IRSAM) under development for the Indus basin

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4 Scientific and Technological Challenges in the Region

Given the novelty of Nexus-EWS as an emergent concept, a variety of fragmented early warning systems are deployed at various scales, community to sub-national to national to transboundary systems. These fragmented EWS do not necessarily account for the nexus, rather the EWS are operational in separate domains, e.g., flood early warning systems, drought early warning systems, and famine early warning systems. The US-AID and NASA have invested considerably in advancing EWS in both Central and South Asia.

In 2010, NASA and US-AID SERVIR program was expanded to Hindu Kush Himalaya, covering most of the mountainous terrain in the Central and South Asia. SERVIR maintains a large, diverse collection of user-tailored geospatial services that use Earth observations and NASA data to inform resilient development. In Hindu Kush Himalaya, with respect to the nexus, SERVIR team has set up a regional drought monitoring and outlook system for South Asia. A prototypical drought monitoring and early warning system for Nepal has been developed under this program, and this prototype is being expanded to other countries Central and South Asia spanning Hindu Kush Himalaya.

Another project under the SERVIR program focuses on enhancing flood EWS. This project aims to build the resilience of vulnerable communities in the Hindu Kush Himalaya region by increasing flood forecast lead times and hosting the information on an interactive web platform. Once fully developed, the service will include an operational 15-day flood forecast based on the downscaled Global Flood Awareness System using a hydrological routing model at designated locations in Bangladesh and Nepal. In addition, this flood EWS will issue warnings on 24 to 48-hour high intensity rainfall events and flash floods. Similar flood EWS is being developed for the Indus basin by BlueEarth and Deltares.

Famine Early Warning Systems Network (FEWS NET), which was initially launched by US-AID and NASA in Africa, was expanded to Afghanistan. The FEWS NET issues monthly reports and maps detailing current and projected food insecurity and alerts on emerging or likely crises. The FEWS NET also issues special reports on factors that contribute to or mitigate food insecurity, including nexus factors pertaining to weather and climate changing induced water variability, as well as markets and trade, agricultural production, conflict, livelihoods, nutrition, and humanitarian assistance.

While SERVIR program inspired drought and flood EWS and FEWS NET generated famine alerts are steps in the right direction, these initiatives have only recently been piloted; and their scaling up across the Central and South Asia will require considerable investments in local capacity to process earth observation data and forecasting models. Bajracharya et al. (2021) provide a decadal synthesis of SERVIR program inspired monitoring and EWS applications in the Hindu Kush Himalaya region. As discussed above, either water (e.g., flood and drought) or food (e.g., famine) related EWS have been piloted; however, no nexus EWS application has yet been derived from the SERVIR program. Nevertheless, the SERVIR program has set up earth observation data capacity in the mountainous region of Central and South Asia to develop Nexus-EWS in the next few years.

Effective design and deployment of Central and South Asian region wide Nexus-EWS still faces considerable scientific and technological challenges. Many of these challenges pertain to the lack of cooperation in data sharing and management planning among riparian partners in transboundary river basins (e.g., Indus and Brahmaputra discussed above). Considerable benefits from scientific and technical cooperation could be potentially drawn by both upstream and downstream riparian partners in transboundary river basins in Central and South Asia; however, narrower geopolitical and compartmentalized policy goals (e.g., energy securitization without regard to water or food security) hamper scientific and technological cooperation. Financial and human resource challenges also compound design and deployment of Nexus-EWS.

5 Satellite Data Revolution and Its Intersection with Traditional Security Dimensions

Widespread availability of satellite and social media data has opened up the possibilities for the design and deployment of convergent technologies such as Nexus-EWS. Yet, a major challenge for quantifying and reducing the uncertainty in the projections of Nexus-EWS concerns the calibration and validation of underlying models against the field scale data. The drought and flood EWS piloted under the SERVIR program and famine EWS piloted under FEWS NET are limited to local scales. Both their scaling up at the Central and South Asian regional scales and their continuous improvement through assimilation of field data (e.g., supply and demand of food, energy, and water across sectors and countries) requires regional cooperation. Due to ongoing geopolitical conflicts in Central and South Asia (e.g., Kashmir, Afghanistan), field data on nexus being collected by national level agencies is not yet shared with scientists working on developing EWS. Without concurrent assimilation of field data in the nexus forecast models, the forecast reliability and accuracy cannot be readily determined. One of the major hurdles in field data sharing concerns the powerful role of traditional energy (e.g., hydropower), water and food securitization lobbies in many Central and South Asian countries.

Furthermore, the satellite data could be limiting due to limits in their spatial, temporal, radiometric, and spectral resolutions. Satellites with higher spatial resolutions tend to have lower temporal resolutions and vice versa. Spectral resolutions of satellites, e.g., Landsat (NASA) and Sentinel (ESA), are driven by science goals of western agencies and not the needs of convergent technologies in developing countries of Central and South Asia. Private sector satellite data could be cost prohibitive. Challenges associated with cloud cover limit the accuracy of Nexus-EWS. To account for gaps in spatial, temporal, radiometric and spectral resolutions, field scale in situ data on water (e.g., stream data), food (e.g., crop data) and energy (e.g., hydropower, wind data) must be made available at the regional scale for developing high resolution operational and tactical scale Nexus-EWS. Traditional securitization approaches, current in Central and South Asia, are certainly unable to stop the information that can be gleaned from open-sourced satellite data, yet the uncertainty of the forecast information derived from the satellite data can be considerably reduced if traditional securitization approach is made more flexible towards scientific and technological cooperation in transboundary river basins. Adoption of open science and data transparency principles in the Central and South Asian countries may eventually be one way to add flexibility in the traditional securitization approach.

6 Geopolitical and Ethical Issues

Widespread design and deployment of convergent technologies such as Nexus-EWS can provide critical and timely information for building resiliency and sustainability. Through mainstreaming Nexus-EWS projections in food, energy, water, and land use planning, ecosystem service management and disaster management at the river basin scales, the risk from extreme events can be potentially reduced and lives saved. Food and energy insecurity are destabilizing factors and increase the likelihood of international crises and conflict. The deployments of Nexus-EWS could support long-term land use and infrastructure planning as well as enable dissemination of early warnings for the near-real time impacts of floods and droughts on food and energy provision. In the face of the risks posed by global climate change, the migration and starvation implications of vulnerable people exposed to food, water, and energy insecurity in Central and South Asia are staggering; and provide strong motivation for future investments in Nexus-EWS. Novel science and environmental diplomacy approaches to build scientific cooperation could also pave the way for deployment of Nexus-EWS.