event 23 Oct 2020

Nexus Blog // Quantifying and visualising inter-dependencies in the water–energy–food nexus

By Declan Conway and Christian Siderius. In this commentary, the authors demonstrate how the physical links between each WEF Nexus element can be quantified by presenting their research outcomes of two new papers on the nexus.

category Research category Nexus Blog tag Nexus Methodology tag Modelling and Assessment
Selous Sand Rivers

Sunset over Rufiji River in Selous Game Reserve, Tanzania, @Panii, CC BY-SA 3.0, via Wikimedia Commons

We often promote coordination as a goal, particularly in relation to policy and planning. But however important it may be, achieving coordination is far from easy.

Enhanced coordination is a key feature of the water–energy–food (WEF) nexus – an agenda that highlights the inter-dependencies that exist between these sectors. Each relies on the other and changes in one can create benefits or trade-offs in the others. By understanding the consequences of decisions across sectors we hope to avoid trade-offs or take advantage of co-benefits. In our globalised world, trade and other linkages create major inter-dependencies across borders – as we are seeing with the rapid spread of COVID-19 and the ongoing socioeconomic upheaval; understanding and managing this web of interconnections is becoming increasingly important.

Quantifying physical links in the nexus

There are two complementary dimensions to understanding the WEF nexus: quantifying the physical links between each element, and unravelling the management and governance structures involved.

Our two new papers on the nexus address the former, in quite different ways: one demonstrates that by integrating datasets to allow a more integrated analysis of WEF interdependencies, we can highlight emerging areas of risk; the other shows how application of visualisation methods can help present to stakeholders the complex relationships that exist across the WEF nexus and hence aid decision-making.

Integrating datasets: the WEF nexus in the Arabian Gulf

The first paper considers the WEF nexus in the Arabian Gulf region, focusing on Kuwait, Qatar and Saudi Arabia. All three have nexus sectors heavily dominated by oil. However, a recent decrease in oil prices has led to significant budget deficits in several countries in the region. The countries rank among the lowest in the world in terms of freshwater resources per person but among the highest in CO2 emissions.

We investigated two geographical scales of the nexus: domestic – how the three sectors are linked within each country; and international – by considering trade imports and exports, including oil exports. Within each country the WEF trade-offs are generally quite limited, as the energy requirements for water and food production are modest compared with other uses – even though some states in the region have developed into world leaders in the application of seawater desalination technology, with an installed desalination capacity of 18 million m3 of water per day, a highly energy-intensive and a costly process.

In Saudi Arabia, nexus trade-offs between food and water have been substantial, with massive overexploitation of fossil groundwater reserves to sustain food production, threatening future water security. Around 2006 this trend was slowed by a policy decision to prioritise water for higher valued industrial and domestic uses, and to abandon an ambition of national food self-sufficiency.

Linking data on food trade and non-sustainable groundwater irrigation

At the international scale, revenues from oil exports enable the region to rely heavily on imports of food products and virtual water (the water used to produce food products) from other countries and seawater desalination to sustain their needs. We linked food trade data with a newly produced global dataset that estimates how much of the water used to irrigate crops comes from non-sustainable sources of groundwater – i.e. locations where irrigation relies on depleting groundwater faster than it is replenished by rain.

We found that substantial rice imports into the region originating in regions where groundwater is being depleted mainly come from India, although Qatar relies strongly on imports from Pakistan. Both India and Pakistan have abundant water resources seasonally, but suffer from declining groundwater levels due to massive over-abstraction.

Aiding decision-making with data visualisation: the WEF nexus in Tanzania’s Rufiji basin

In the second paper, we study a major river basin in Tanzania, the Rufiji. This river supplies a high proportion of the country’s electricity through hydropower, supports the agricultural livelihoods of millions of farmers, and masses of biodiversity as it flows through several wildlife parks. The river basin is targeted for socioeconomic development as part of what is termed a ‘development corridor’ that aims to enhance investment in agricultural ventures in several cluster areas. In 2016 a decision was made to go ahead with a long-mooted plan for a major hydropower reservoir, to be called the Julius Nyerere Hydropower Project, named after Tanzania’s first president.

The multiple uses of water in the river basin have complex interdependencies. For example, major trade-offs exist between upstream abstractions for irrigation, which reduce water availability for hydropower, and dam infrastructure, which disrupts the downstream natural flow regimes of the river that support livelihoods and wildlife in the Rufiji Delta.

Informing and involving non-specialist stakeholders in decisions

The consequences of decisions in the Rufiji basin cut across many sectors and can be hard to predict and even harder to communicate to non-specialists – who are the ones making the decisions and living with the outcomes. These stakeholders therefore need to be involved and informed about underlying assumptions about situations and where value judgements are present. This creates another trade-off: between the complexity and comprehensiveness of an assessment and its usability.

Our work approached this by seeking guidance on what various stakeholders felt were important services that development in the basin should achieve sustainably (performance indicators) and then modelling many thousands of combinations of options to identify which ones worked best across the different performance indicators. This is a process known as multi-objective optimisation.

The indicators we settled on after consultation were reliable hydropower power production on monthly and annual bases, reliable water availability to support irrigation expansion, and a measure of river flow disruption with impacts on downstream ecosystems. Four river basin development scenarios were examined: the current river basin plus only the major hydropower dam; a synergistic scenario with optimised irrigation expansion; new dams and their operations; and a full development scenario, assuming all planned infrastructure expansion.

Data visualisation to aid decision-making

In visualising the scenarios and their performances on parallel axes diagrams that portray many results at the same time, the trade-offs were revealed. This visualisation helps decision-makers appreciate the consequences of their decisions and how they can be resolved with minimal sacrifice of performance in other sectors. Our future work will take this interaction further by presenting results interactively with stakeholders so that they can re-arrange the position of the axes and filter out results that are felt to be unacceptable.

Overall, the Rufiji river basin has the capacity to support a range of development plans. There are important basin-scale interdependencies, in particular where performance indicators are impacted at the planned major dam, due to the cumulative effects upstream of unregulated irrigation expansion and inefficient management.

Conclusions

These examples show how a nexus approach can reveal that a country’s food imports are associated with unsustainable agricultural practices and where the use of innovative modelling and visualisation techniques can provide opportunities to convey the complex outcomes of decisions, capturing alternative perspectives and values. Coordination is hard to achieve, but new datasets and innovative methods of visualisation offer promise in addressing at least some of the barriers.

This article was originally published on the website of the Grantham Research Institute and is republished with the authors permission.

Declan Conway is a Professorial Research Fellow at the Grantham Research Institute. Christian Siderius was formerly a Research Fellow at the Grantham Research Institute and now works for Uncharted Waters Research in Sydney, Australia. The views in this commentary are those of the authors and do not necessarily represent those of the Grantham Research Institute.

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