The recent intensification of international trade has led to a growing disconnection between consumer demand for goods and services and the water resources that support them. The important role of household demands on the exploitation of distant freshwater resources is widely recognized, yet the different socioeconomic drivers underlying the trends in domestic and foreign water use remain poorly quantified. In this work, the main mechanisms governing the exploitation of domestic and foreign freshwater resources are quantified by undertaking a structural decomposition analysis over the period 1994–2010 in 186 countries. Our results show that growth in affluence has been the main determinant of rising water consumption trends worldwide. There are indications that consumers in developed countries tend to increase their affluence by intensifying the use of foreign water resources. Conversely, affluence growth in developing regions seems to rely on the exploitation of local water resources revealing a significant imbalance among economies. The growth of affluence and population has been only partially offset by improvements in the intensity of blue water use by producers and, to a lesser extent, by changes in the interdependences among sectors.

Abstract. To support national and global assessments of water use in agriculture, we build a comprehensive database of country-specific water footprint and virtual water trade (VWT) data for 370 agricultural goods. The water footprint, indicating the water needed for the production of a good including rainwater and water from surface water and groundwater bodies, is expressed as a volume per unit weight of the good (or unit water footprint, uWF) and is here estimated at the country scale for every year in the period 1961–2016. The uWF is also differentiated, where possible, between production and supply, referring to local production and to a weighted mean of local production and import, respectively. The VWT data, representing the amount of water needed for the production of a good and virtually exchanged with the international trade, are provided for each commodity as bilateral trade matrices, between origin and destination countries, for every year in the period 1986–2016. The database, developed within the CWASI project, improves upon earlier datasets because it takes into account the annual variability of the uWF of crops, it accounts for both produced and imported goods in the definition of the supply-side uWF, and it traces goods across the international trade up to the origin of goods' production. The CWASI database is available on the Zenodo repository at https://doi.org/10.5281/zenodo.4606794 (Tamea et al., 2020), and it welcomes contributions and improvements from the research community to enable analyses specifically accounting for the temporal evolution of the uWF.

World freshwater ecosystems are significantly deteriorating at a faster rate than other ecosystems. Water withdrawals are recognized as one of the main drivers of growing water stress in river basins worldwide. Over the years, much effort has been devoted to quantify water withdrawals at a global scale; however, comparisons are not simple because the uneven spatiotemporal distribution of surface water resources entails that the same amount of consumed water does not have the same environmental cost in different times or places. In order to account for this spatiotemporal heterogeneity, this work proposes a novel index to assess the environmental cost of a withdrawal from a generic river section. The index depends on (i) the environmental relevance of the impacted fluvial ecosystem (e.g., bed-load transport capacity, width of the riparian belt, biodiversity richness) and (ii) the downstream river network affected by the water withdrawal. The environmental cost has been estimated in each and every river section worldwide considering a reference withdrawal. Being referred to a unitary reference withdrawal that can occur in any river section worldwide, our results can be suitably arranged for describing any scenario of surface water consumption (i.e., as the superposition of the actual pattern of withdrawals). The index aims to support the interpretation of the volumetric measure of surface water withdrawal with a perspective that takes into account the fluvial system where the withdrawal actually occurs. The application of the index highlights the river regions where withdrawals can cause higher environmental costs, with the challenge of weighting each water withdrawal considering the responsibilities that it has on downstream freshwater ecosystems.

We quantify the impact of food consumption on local and foreign water resources through an indicator of the environmental value of the riverine water. This indicator takes into account both the local environmental relevance of the fluvial area where water is withdrawn (biodiversity richness, riparian vegetation, sediment transport, etc) and the downstream effects of water withdrawals. In the 1986-2013 period, food consumption has more than doubled its impact on foreign riverine environments, but still the international trade reduces the pressure of food consumption on global river system by 11%, as compared to an ideal situation where all food is produced locally. We also show the geography of country (or individual) responsibility on the environmental changes of world rivers. Hotspots of food-related river-environment degradation are found in Australia, Pakistan, South Africa, and Spain.

Abstract. To support national and global assessments of water use in agriculture, we build a comprehensive and harmonized database of water footprint and virtual water trade (VWT) data for hundreds of agricultural goods. The water footprint, indicating the water needed for the production of a good, including rainwater and water withdrawals, is expressed as a volume per unit weight of commodity (or unit water footprint, uWF), which is here estimated at the country scale for every year in the period 1961–2016. The uWF is also differentiated, where possible, between production and supply, referring to local production only and to a mixed role of local production and import, respectively. The VWT data, representing the amount of water needed for the production of a good and virtually exchanged with the international trade, are provided for each commodity as bilateral trade matrices, between origin and destination countries, for every year in the period 1986–2016). The database, developed within the EU-funded CWASI project, improves upon earlier datasets because it takes into account the annual variability of the uWF of crops, it accounts for both produced and imported goods in the definition of the uWF and it traces goods across the international trade up to the origin of goods' production. The CWASI database is available on the Zenodo repository at https://doi.org/10.5281/zenodo.3987468 (Tamea et al., 2020) and welcomes contributions and improvements from the research community to enable analyses specifically accounting for the temporal evolution of the uWF.

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