Did you know that the global population quadrupled in less than 100 years? While we were only 2 billion people on Earth in 1928, we reached 8 billion in 2023 (Ritchie et al., 2023). An increasing global population, predicted to reach more than 9 billion by 2050, means the world will have to produce 60 per cent more food (FAO, 2025) than only 20 years ago in 2005 (FAO, 2009) on deteriorating soil and with already dwindling water resources. That said, food production is not the only factor closely linked with water. By 2035 we will need 50 per cent more energy. Presently already a quarter of the total energy consumed on Earth is used for food production. Energy is also closely linked to water, because energy is used to collect and treat water, and water is used to produce energy such as in the case of hydropower (FAO, 2025). By 2050 Water demand worldwide is expected to rise by 55 per cent. Today agriculture is already the largest user of freshwater, consuming 72 per cent of the global resources (UN-Water, 2024). With rising demand for the interdependent water, energy and food resources, a sustainable and integrated approach must be a priority. It becomes evident that achieving the United Nations Sustainable Development Goals (SDGs) will largely depend on how we manage the Water-Energy-Food (WEF) Nexus (UN-Water, 2024).

The Water-Energy-Food Nexus

The idea of a Water-Energy-Food (WEF) Nexus was originally proposed at the Bonn 2011 Conference organised by Germany, in anticipation of Rio+20, a United Nations Conference on Sustainable Development. The nexus emphasizes a cross-sectoral perspective for addressing issues related to water, energy and food (McNally et al., 2019). The drivers of the WEF Nexus include a growing population with diversifying diets, industrial development, agricultural transformations, sectoral policies, urbanisation and climate change (FAO, 2025) as visualised in figure 1.

The Food and Agriculture Organization (FAO) stresses the need to develop and to focus on sustainable agriculture and food security for future generations. For this purpose, FAO encourages solar-powered irrigation, reducing food waste as well as nexus assessments in transboundary basins (FAO, 2025). The United Nations calls for governments to preserve ecosystems, use renewable energy sources and incorporate the WEF Nexus in their decision-making (UN-Water, 2024). Managing the WEF Nexus well, would mean progress towards achieving Sustainable Development Goals 2 – Zero Hunger, 6 – Clean Water and Sanitation and 7 – Affordable and Clean Energy (Lodge, Dansie, and Johnson, 2023). Further SDGs connected with the nexus are SDG 13 – Climate Action, 14 – Life below Water and 15 – Life on Land (FAO, 2024).

To monitor and manage these scarce resources as well as the progress towards the associated reporting goals, large datasets from globally available data sources are taken into consideration. Global data sources for the WEF Nexus include global observation networks that collect data on Earth from observing platforms, reanalysis datasets that integrate observation data with models, land surface models that simulate Earth’s processes and satellite remote sensing, which collects data from a distance (Lodge, Dansie, and Johnson, 2023; World Meteorological Organization, 2025).

Satellite data sources to monitor the WEF Nexus

Space technology offers powerful tools to address numerous of the WEF Nexus challenges. Remote sensing is directly used for Member State reporting on the SDGs for only a few indicators such as SDG 6.4.2 (freshwater), 6.6.1 (water-related ecosystems), 11.3.1 (land consumption), 14.3.1 (marine acidity), 15.1.1 (forest area), 15.3.1 (land degradation), 15.4.2 (mountain green cover), considering that as of 2020, there are 231 indicators in total (O’Connor et al., 2020). The potential for monitoring and managing supported by space technologies is beyond its current use. In fact, reports like the “Compendium of Earth Observation contributions to the SDG Targets and Indicators” from May 2020, recognise that satellite-based Earth observation can also be indirectly used to track progress towards the SDGs. Specifically, variables based on Earth observation data are monitored and reported on (O’Connor et al., 2020).

Among the variables that can be observed from space directly or indirectly to address the water component in the WEF Nexus are evapotranspiration, groundwater, lake storage, streamflow, precipitation, water surface area and soil moisture. Crop yield and crop area are relevant variables for the food component of the WEF Nexus. Further variables that are related to the food component are irrigation estimates, monitoring of crop diseases and the indirect monitoring of food security such as through crop yield estimates based on crop conditions. In terms of the energy component of the WEF Nexus, renewable energies should be considered, specifically solar energy, hydropower, wind, geothermal and biomass. Satellite remote sensing provides solar irradiance products for solar energy, elevation head and flow are considered for hydropower, offshore and onshore wind speed to estimate wind energy, certain surface features for geothermal energy and vegetation types and horizontal canopy cover for biomass. Many of these variables use additional data sources apart from satellite remote sensing for more precise estimations (Lodge, Dansie, and Johnson, 2023).

Besides satellite remote sensing, surface-based platforms also provide observational data. Surface-based platforms or stations observe climatological, meteorological and hydrological conditions, among others. Global observation networks are a series of these observing stations that monitor and assess the Earth’s systems. An example would be the World Meteorological Organization (WMO) Hydrological Observing System (WHOS), which concerns itself with hydrological observations, including data exchange and cooperation. Global observation networks can be combined with reanalysis datasets, for instance, for the purpose of climate monitoring (World Meteorological Organization, 2025).

Reanalysis datasets are a synthesis of past weather and climate observations with present weather forecasting models. Reanalysis aims to fill any gaps in datasets and provide a complete record on Earth system observations for a certain period. An example of a reanalysis dataset is ERA5 produced by Copernicus Climate Change Service (C3S), through the European Centre for Medium-Range Weather Forecasts (ECMWF). ERA5 is a climate reanalysis dataset that includes Earth system data from 1940 to the present. However, a disadvantage of reanalysis datasets such as with ERA5 is that periods or regions with infrequent observations are possibly less reliable (European Centre for Medium-Range Weather Forecasts, 2023).

Aside from reanalysis data, modelling also plays a crucial role in monitoring resources. Land surface models are numerical models for simulating processes on the Earth's surface (Lodge, Dansie, and Johnson, 2023). They combine both in situ measurements and satellite observation data to model changes due to anthropogenic and naturally occurring activities on the Earth’s surface. Land surface models are especially relevant for studying the energy and water cycle. An example of a land surface model would be the National Aeronautics and Space Administration (NASA) Land Data Assimilation Systems (LDAS), that provides estimates for the variables soil temperature, soil moisture, runoff and evapotranspiration (NASA, 2011).

When there is a lack of ground-based or in situ observations such as in remote areas, satellite remote sensing comes into play. Satellite remote sensing can provide most of the globally available data for the WEF Nexus, although sometimes including data from global observation networks, reanalysis datasets or numerical models can provide additional valuable insights. Satellite remote sensing involves collecting data about an area, in this case, the Earth’s surface at a distance. Satellite remote sensing can be active or passive, meaning energy is transmitted towards the object by a sensor or energy emitted by the object is detected by the sensor, respectively (Lodge, Dansie, and Johnson, 2023).

In general, a variety of datasets exist that can help us monitor variables associated with the WEF Nexus, and space technology plays a crucial role in this regard. However, there are also challenges related to the use of the various datasets that exist in relation to the WEF Nexus. These include a lack of interoperability between systems, data fragmentation and information privacy concerns to name just a few (World Economic Forum, 2024). Rejane Souza, Senior Vice-President of Yara International, a company focusing on crop nutrition, highlights that:

“To surmount these obstacles, collaborative efforts are essential, focusing on the development of standardized protocols, improving data literacy and establishing secure frameworks.” - Rejane Souza (World Economic Forum, 2024).

One of these obstacles, data fragmentation, can be caused by decentralised decision-making. When decisions are taken by numerous stakeholders, data to inform decisions is sometimes distributed across multiple platforms. Data fragmentation leads to information being spread throughout divergent formats and storage locations. It can result in data inconsistencies and a distrust among stakeholders. One of the strategies to overcome data fragmentation and facilitate data sharing between institutions is to cultivate centralised platforms, allowing for the information to be accessible from one place (Ibitola, 2024). This also applies to data collected through satellite remote sensing, which can be spread across different platforms, and a comprehensive overview of globally available data sources is only a recent development for the WEF Nexus (Lodge, Dansie, and Johnson, 2023).

Case studies on remote sensing for the Water-Energy-Food Nexus

Numerous experts make use of globally available data sources for the purpose of conducting research and writing papers on the use of remote sensing for the Water-Energy-Food (WEF) Nexus. The researchers often focus on two components of the nexus, however, some include all three components of water, energy and food.

Koppa and Gebremichael (2020) aimed to improve hydrological modelling for the WEF Nexus by comparing univariate and multivariate calibration of the variables soil moisture, streamflow and evapotranspiration. By performing hydrological modelling of these variables, the interdependencies of the water, energy and food components of the nexus can be better understood. For this purpose, the researchers calibrated the NASA Noah-MP hydrological model to improve its application in the Mississippi River basin in the United States. Remotely sensed soil moisture estimates were acquired from the European Space Agency (ESA) Climate Change Initiative (CCI) dataset. Satellite remote sensing estimates for evapotranspiration were taken from the Global Land Evaporation Amsterdam Model (GLEAM) dataset. When comparing satellite remote sensing estimates with ground-based data, the experts found that GLEAM evapotranspiration values agreed with in situ measurements, while ESA-CCI soil moisture data underestimated the observed values. Univariate calibration of the hydrological model with only streamflow increased the accuracy of this variable yet decreased the accuracy of soil moisture and evapotranspiration. Multivariate calibration, on the other hand, maintained the accuracy of all three variables. In summary, the researchers recommend multivariate calibration for hydrologic models for WEF Nexus studies.

Zhou et al. (2020) investigated agricultural production in the groundwater-dependent Ogallala Aquifer Region (OAR) in the United States, which included recognising conflict hotspots through remote sensing. Conflict hotspots in this case occur when water resources are declining and agricultural production is growing. Frequent causes are expanding crop production, involving greater irrigation demand. They often result in an aquifer's depletion. The researchers aimed to suggest practices for sustainable agriculture based on remote sensing data relating to the food and water aspects of the WEF Nexus. Specifically, the experts used satellite remote sensing estimates of the total water storage (TWS) and the net primary production (NPP) for agriculture within the OAR. TWS is a combination of groundwater and surface water, while NPP is the accumulation of biomass or carbon. Earth observations from NASA Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow On (GRACE-FO) missions were used for TWS. Estimates from NASA Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-based sensor were used for NPP. Ultimately, the researchers found conflict hotspots in the southern areas of the OAR. They suggest water management practices such as transitioning to rainfed crops and boosting irrigation efficiency.

Song et al. (2022) examined water scarcity and irrigation in agriculture on a basin scale for the nexus. The experts linked the hydrological model MODFLOW-NWT with potential evapotranspiration values from NASA MODIS sensors. The hydrological model recreated groundwater and surface water irrigation practices in the study area. The study scope was an arid endorheic lake basin in China, the Yanqi Basin, where 90 per cent of the total water consumption goes to irrigation. Intensive irrigation practices in an endorheic basin can result in water depletion in the area. Eventually, this may cause a drying up of the lake and environmental degradation. The experts warn that boosting agro-economic benefits in the Yanqi Basin through immoderate fertilizer usage would come at the expense of nitrate pollution. The aims for the basin are to increase the possible cultivation area, maintain agro-economic benefits and to reduce total nitrogen loading. The researchers hope that their modelling framework aids sustainable development planning in the basin. The water management solutions identified by Song et al. (2022) allow to enhance irrigation water distribution and crop planting structure.

Alam et al. (2019) investigated energy and water use in agriculture, specifically for extracting groundwater and crop irrigation in Central Valley, California. The Central Valley is an important agricultural area in the United States. About half of their produce of nuts, fruits and vegetables are grown there. In the last two decades, the area has experienced periods of drought, which combined with increased water use for irrigation has put a strain on the resources of water and energy. To facilitate the understanding of the roles of energy and water in the WEF Nexus, the experts assessed the energy and water footprints in the area through agricultural land use data, satellite remote sensing and hydrological modelling. Satellite remote sensing offers the advantages of providing data that covers an extended period and in higher spatial resolution as well as bridging any data gaps. The experts used satellite data products such as from Landsat 7 Enhanced TM Plus (ETM+), Landsat 8 Operational Land Imager (OLI) and Tropical Rainfall Measuring Mission (TRMM). In summary, the experts found that the southern regions of the Central Valley had experienced the most negative effects of the droughts in the area, partly due to water intensive crops. With a higher water footprint, the energy footprint was also high in comparison to other areas in the region, because of the energy consumed by groundwater pumping.

McNally et al. (2019) discussed the implementation of a crop monitor by Group on Earth Observations Agricultural Monitoring (GEOGLAM) and Agricultural Market Information System (AMIS). The Group of Twenty (G20), an international forum of 19 countries and two regional bodies for economic cooperation, wished to enable early warnings and forecasts in food production and address food price volatility. Consequently, the global Crop Monitor for AMIS (CM4AMIS) was introduced in 2013. CM4AMIS allows for monthly reports with written summaries on crop conditions, graphs and maps based on the NASA MODIS Normalized Difference Vegetation Index (NDVI). The map in figure 2 shows worldwide wheat crop conditions and drivers for November 2024. As can be seen from the map, the wheat harvest in Europe is under mixed conditions, with some countries experiencing more favourable conditions than others. The main drivers of these crop conditions are delayed onset and wet or dry weather, depending on the region. While wheat sowing in the United States is mainly under favourable conditions, the crop conditions in Australia are mixed (GEOGLAM Crop Monitor, 2024; Ministry of External Affairs, Government of India, 2025).

Apart from multiple case studies focusing on the use of remote sensing for the WEF Nexus, numerous projects encourage the use of satellite data and modelling to manage the nexus. The below overview provides some examples:

• Integrated Snow Monitoring System (SnowSAT), which measures snow accumulation to determine efficient hydropower production. 
• Integrated information services that will be used primarily by farmers for easy information access. 
• Agrivoltaic systems for efficient solar energy use for crop production.
• Irrigation management system, which provides services for Swedish farmers with irrigation systems. 
• e-ReWater MENA, a tool for evaluating possible water reuse in Lebanon and wastewater management in the Middle East and North Africa (MENA) region.
• WE-ACT, a project that aims to determine efficient water allocation in the transboundary Syr Darya river basin in Central Asia.
• WaPOR, a project that assesses water and land productivity to support sustainable crop production.
• Health impact of urban water access (URBEN), a project focusing on urban development in the town of Leh, India, that combines energy efficiency and water resource preservation.
• IN-SOURCE, a project resulting in modelling and data tools for sustainable infrastructure derived from the example cities of New York, Vienna and Ludwigsburg

(Group on Earth Observations, 2024; International Water Management Institute, 2025; JPI Urban Europe, 2021; Technical University of Munich, 2015).

Apart from projects encouraging the use of space technology for managing the WEF Nexus, Lodge, Dansie, and Johnson (2023) argue that creating a database from multiple data sources is crucial to the nexus, allowing for a more comprehensive overview of available products. Zhou et al. (2020) find discrepancies between satellite remote sensing estimates and agricultural data, specifically agricultural statistics for crop yield and crop area, suggesting a need for more effective data fusion like with machine learning. It is noteworthy to mention that the water component is more studied than the food component through satellite remote sensing in the WEF nexus. It is, therefore, important that future studies aim at alleviating the difference in which degree the different components of the nexus are studied. More publications should aim at investigating all three components of the nexus through space technology. In the meantime, space-based monitoring of variables related to the nexus aids in understanding the interactions between water, energy and food (Lodge, Dansie, and Johnson, 2023).

Example case using space-based monitoring of the Essential Climate Variable soil moisture

Based on interactions with other variables used for water, energy and food, soil moisture is one of the pivotal variables in the nexus. Soil moisture estimates can be used in hydrological modelling to indicate runoff and for irrigation planning in agriculture. Satellite remote sensing can often only measure the upper five centimetres of soil depth, yet, measurements of the upper soil layer are potentially insufficient for nexus studies. Therefore, satellite remote sensing data is combined with other data sources like reanalysis datasets and land surface models to provide estimates. Satellite remote sensing performance is also reduced in areas of dense vegetation, leading to the use of land surface models in that case (Lodge, Dansie, and Johnson, 2023).

Soil moisture was identified as an Essential Climate Variable (ECV) in 2010 and became a part of the European Space Agency’s (ESA) Climate Change Initiative (CCI). The project aims to publish updated climate data collected from multiple sources. The ESA CCI soil moisture product combines 14 missions’ datasets in total, including ESA Soil Moisture and Ocean Salinity (SMOS) and NASA Soil Moisture Active Passive (SMAP) (ESA, 2024b).

The ESA SMOS mission was launched in 2009 to study the Earth’s water cycle and allow accurate climate and weather predictions. It involves an Earth Explorers satellite monitoring sea surface salinity and soil moisture over land. SMOS uses a Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument to measure the amount of water in the soil (ESA, 2024a).

The NASA SMAP mission was launched in 2015 and involves an Earth satellite with a radiometer for measuring frozen/thawed ground and soil moisture (NASA, 2024). SMAP Level 4 (L4) has the advantage that it can measure soil moisture below 5 cm, unlike most other remote sensing satellites (Lodge, Dansie, and Johnson, 2023). A past mission from NASA, namely GRACE and its current next-in-line GRACE-FO satellites are also used for water observations, including of the soil moisture variable (Zhou et al., 2020).

Satellite data is often merged to form a more complete data product such as the ESA CCI, which was mentioned earlier. When comparing spatial resolution, SMAP has a higher spatial resolution of nine kilometres than ESA CCI and SMOS with 0.25° and 40-50 km spatial resolutions, respectively. ESA CCI and SMAP are revisited daily and SMOS every three days (Lodge, Dansie, and Johnson, 2023) (Table 1, see below). In the table, RS and LSM are acronyms for remote sensing and land surface models, respectively (Lodge, Dansie, and Johnson, 2023).

Lastly, in 2025, ESA will launch the Hydrological Global Navigation Satellite System (HydroGNSS) scout mission to measure multiple climate variables, including the variable soil moisture. The mission has two satellites that may provide an alternative to NASA SMAP and ESA SMOS missions when these reach the end of their life. The HydroGNSS mission can provide complementary information such as on forest biomass to the ESA Biomass mission (Space4Climate, 2024).

Conclusion

A growing population and the resulting pressure on resources underline the importance of acting towards achieving the Sustainable Development Goals. Space technology allows for the monitoring of these resources and for the modelling of processes on the Earth's surface. Satellite remote sensing data is available in near-global spatial coverage and at different temporal resolutions, allowing its use for many purposes connected to the nexus. Multiple case studies demonstrate the effective use of satellite remote sensing for hydrological modelling, recognising water scarcity, sustainable water management practices and crop monitoring. Multiple satellites are engaged in measuring variables such as soil moisture to understand and address the three components of the nexus. NASA SMAP and ESA SMOS are some of the leading missions in estimating the variable soil moisture. In conclusion, the use of space technology benefits the Water-Energy-Food (WEF) Nexus in many ways.