Unsustainable groundwater use for global food production and related international trade

Carole Dalin,Timothy R Green,Makoto Taniguchi

doi:10.1017/sus.2019.7

Abstract

Non-technical summary Most of the water humans consume is for agriculture. Rapidly increasing water demand has led to overexploitation of water resources in many important food-producing regions. In particular, growing groundwater-based irrigation causes potentially damaging depletion. Food systems are increasingly globalized, leading to large export-oriented production. Much research has focused on quantifying the amount of water resources embedded in traded products, but less attention has been given to the role of groundwater use and the related sustainability of agriculture globally. We assess current knowledge of virtual water trade in light of groundwater use and sustainability and highlight remaining challenges in this field.

Highlights

Water on Earth is a limited resource, with more or less quickly renewable reservoirs
We have highlighted key issues related to tracking groundwater use in food production and trade, discussing the complexity of both sustainability metrics for crop water use and groundwater storage and flows, and some difficulties in their estimation
The distinct consideration of groundwater resources as a supply of irrigation water is only recently emerging in Virtual water trade (VWT) studies

Summary

Introduction

Water on Earth is a limited resource, with more or less quickly renewable reservoirs. Such indicators can be related to particular agricultural products and combined with trade data to include aspects of environmental impact and sustainability of water use in VWT analysis These indicators have highlighted regions with major water insecurity through analyses at country (Seckler, 1999) or grid levels (Mekonnen & Hoekstra, 2016), on an annual (Wada et al, 2014) or monthly basis (Hoekstra et al, 2012; Scherer et al, 2016) and integrating both temporal scales (Brauman et al, 2016) and studying water availability and sustainability outcomes under a range of scenarios (Wada et al, 2014). They introduced the concept of the groundwater footprint, defined as the area-averaged ratio of abstraction to recharge (where the contribution to environmental streamflow is first deduced from the recharge), with data sources and models similar to those used by Wada et al (2010) (i.e., PCR-GLOBW and national groundwater use statistics). Tuninetti et al (2019) introduced the crop-specific ‘water debt’ indicator, comparing crop water use to availability of green, surface water and groundwater resources from grid cell to watershed and at a national scale

Quantification of groundwater depletion for food production and trade

Findings

Conclusions and future research directions