The environmental cost of a reference withdrawal from surface waters: Definition and geography

Abstract

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.

Global virtual water trade and the hydrological cycle: patterns, drivers, and socio-environmental impacts

“…Indeed, the quantitative analysis of water footprint and VWT focuses on water consumption and therefore does not inform about the sustainability of water resource exploitation (Gawel and Bernsen 2013). Thus, water footprint and VWT analyses need to be integrated with a water balance approach to compare the consumption rates with locally available water resources Mekonnen and Hoekstra 2016;Soligno et al 2017;Rosa et al 2018a). Indeed, literature on the globalization of water resources may miss a description of the phenomenon of VWT in the context of its hydrological implications.…”

“…lakes and aquifers), may have detrimental impacts on the aquatic habitats and water sustainability. Recent research has investigated the extent to which the closure of the yield gap of major crops collides with environmental health because it threatens environmental flows (Soligno et al 2017, Rosa et al 2018a. In these conditions the overexploitation of water resources may lead to increased pollution and irreversible losses of biodiversity (e.g.…”

The globalization of riverine environmental resources through the food trade

“…The latter percentage was assumed constant for all the commodities produced in a given country due to a lack of reliable product-specific Rs data. Finally, each cubic meter of water withdrawn from surface water systems was converted into its corresponding environmental impact, by considering the country-specific EC introduced by Soligno et al [31], in order to take into account the expected impact that these withdrawals have on local river ecosystems.…”

“…According to Soligno et al [31], in a given river section the EC per unit length (ec w ) of a unitary water withdrawal W is defined to be proportional to the river discharge reduction caused by the withdrawal. Namely, W Q ec ec w max = · , where ec max is the maximum EC per unit length, which occurs when the entire river discharge (Q) is depleted.…”

“…By considering 270 food and agricultural goods, we estimate the irrigation water supplied from surface water sources over the period 1986-2013. Then, building on the concept of Environmental Cost (EC) introduced by Soligno et al [31] we consider (i) the effect that the river discharge reduction has on different fluvial characteristics (e.g. transport of sediments and chemicals, riparian belt width, biodiversity richness, etc), and (ii) the downstream propagation effect of the withdrawal.…”