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Imported water risk: the case of the UK

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2016 Environ. Res. Lett. 11 055002

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Environ. Res. Lett. 11 (2016) 055002 doi:10.1088/1748-9326/11/5/055002

PAPER

Imported water risk: the case of the UK

ArjenYHoekstra andMesfinMMekonnenTwenteWater Centre, University of Twente, TheNetherlands

E-mail: a.y.hoekstra@utwente.nl

Keywords:water footprint, virtual water trade, water risk, water security, water dependency, food security

Supplementarymaterial for this article is available online

AbstractWhile thewater dependency of water-scarce nations is well understood, this is not the case forcountries in temperate and humid climates, even though various studies have shown thatmany ofsuch countries strongly rely on the import of water-intensive commodities from elsewhere. In thisstudywe introduce amethod to evaluate the sustainability and efficiency of the external waterfootprint (WF) of a country, with theUK as an example.We trace, quantify andmap theUK’s directand indirect water needs and assess the ‘importedwater risk’ by evaluating the sustainability of thewater consumption in the source regions. In addition, we assess the efficiency of thewaterconsumption in source areas in order to identify the room forwater savings.Wefind that half of theUK’s global blueWF—the direct and indirect consumption of ground- and surfacewater resourcesbehind all commodities consumed in theUK—is located in places where the blueWF exceeds themaximum sustainable blueWF. About 55%of the unsustainable part of theUK’s blueWF is located insix countries: Spain (14%), USA (11%), Pakistan (10%), India (7%), Iran (6%), and SouthAfrica (6%).Our analysis further shows that about half of the global consumptiveWFof theUK’s direct andindirect crop consumption is inefficient, whichmeans that consumptiveWFs exceed specifiedWFbenchmark levels. About 37%of the inefficient part of theUK’s consumptiveWF is located in sixcountries: Indonesia (7%), Ghana (7%), India (7%), Brazil (6%), Spain (5%), andArgentina (5%). Insome source countries, like Pakistan, Iran, Spain, USA and Egypt, unsustainable and inefficient bluewater consumption coincide.We find that, by lowering overall consumptiveWFs to benchmarklevels, the global blueWFofUK crop consumption could be reduced by 19%.We discuss fourstrategies tomitigate importedwater risk: becomemore self-sufficient in food; diversify the import ofwater-intensive commodities, favouring the sourcing fromwater-abundant regions; reconsider theimport of water-intensive commodities from the regions that aremost severely water stressedaltogether; and collaborate internationally with source countries with unsustainable water usewhereopportunities exist to increase water productivity.

1. Introduction

Since the beginning of this century there is a growingawareness that freshwater is a global resource, eventhough freshwater is still mostly considered andmanaged as a local resource (Hoekstra 2011,Vörösmarty et al 2015). This is very different from oil,which is broadly perceived as a resource of strategicinternational importance. The degree of dependenceon oil imports is generally an area of governmentalconcern. In the case of freshwater, however, depend-ence on external water resources is still under the radar

for most governments. Many countries though areheavily reliant on the import of water-intensivecommodities from elsewhere. Dalin et al (2012) andCarr et al (2012) estimate that between 1986 and 2007the number of trade connections and the volume ofwater associated with global food trade more thandoubled. Similarly, Clark et al (2015) find a globaltrend towards an increased dependence on foreignwater resources between 1965 and 2010. Suweis et al(2013) show that international water dependencies asthey exist cannot be assumed to continue into thefuture given growing water scarcity (WS) in the

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countries currently using substantial volumes of waterfor producing export products.

As first shown by Hoekstra and Hung (2002), thewater footprint (WF) of human consumption within acountry consists of an internal WF, referring to thewater use within the country itself for making pro-ducts that are consumed domestically, and an externalWF, referring to theWF in other countries for makingproducts imported by and consumedwithin the coun-try considered. Thus, trade in water-intensive com-modities like crops results into so-called virtual water(VW) flows between exporting and importing regions(Hoekstra 2003). Various global assessments of theWFs of nations and international VW flows have beenpublished: Hoekstra and Hung (2002), Hoekstra andChapagain (2007b, 2008), Fader et al (2011), Mekon-nen and Hoekstra (2011b), Hoekstra and Mekonnen(2012) and Chen and Chen (2013). These studies showthat all countries have partly externalised their WF,albeit to different extents. According to Hoekstra andMekonnen (2012), European countries like Italy, Ger-many, the United Kingdom, and the Netherlands haveexternal WFs contributing 60%–95% to their totalconsumption-related WF, while the external WFs ofcountries like Chad, Ethiopia, India, Niger, DRCongo, Mali, Argentina, and Sudan are smaller than4%of their total footprint.

In this paper we aim to show that dependence onexternal water resources can constitute a substantialrisk for a national economy and should therefore be areason for governmental concern as well. The risk ofexternal water dependence is known for highly water-scarce countries, like those in the Middle East andNorth Africa (Allan 2001, Fader et al 2013), but hasgone unnoticed so far in more water-abundantregions.We take theUK as a case to trace, quantify andmap the direct and indirect water needs of a popula-tion and consequently assess the ‘imported water risk’by evaluating the sustainability of the water consump-tion in the source areas. Next, we assess the efficiencyof the water consumption in the source areas in orderto identify the room for water savings in crop produc-tion. Efficiency is measured by comparing the actualWFs of crops to certain specified benchmark levels.Potential water savings are calculated by consideringthe reduced water consumption if the WFs in cropproduction in the source regions of theUK’s foodwerelowered to the benchmark levels.

The analysis undertaken in this study goes con-siderably beyond earlier studies. Regarding the firststep of the research, quantifying, tracing and mappinga country’s direct and indirect water needs, there areseveral previous national WF studies analysingnational VW trade and the external WF of nationalconsumption, but these studies identified sourcecountries only, without further tracing within thesource countries—see for example Hoekstra and Cha-pagain (2007a) and Van Oel et al (2009) for the Neth-erlands, Chapagain and Orr (2008) for the UK, Schyns

and Hoekstra (2014) for Morocco and Dalin et al(2014) for China—or did quantify VW imports butnot specifically traced the source countries of impor-ted water-intensive products at all—e.g. Ma et al(2006), Liu et al (2007) and Dalin et al (2014) forChina, Bulsink et al (2010) for Indonesia, Yu et al(2010) for the UK and Aldaya et al (2010) for Spain.Tracing the origin of products is relevant if it comes toassessing the sustainability and efficiency of water useat the place of origin, because WS and water manage-ment practices can widely vary within countries. A fewstudies mapped the external WF of a country’snational consumption at a high resolution of 5×5arc minute, but the method to trace down the sourceregions of imported products was rather crude, basedon tracing imported food back to themain agriculturalareas rather than tracing crop by crop—see HoekstraandMekonnen (2012) for the US, Ercin et al (2013) forFrance, Mekonnen and Hoekstra (2014a) for Kenya,and Pahlow et al (2015) for South Africa. The currentwork considers the origin of production crop by crop.Regarding the second step of the research, assessingthe sustainability and efficiency of the water consump-tion in the source areas, this is the first time this is donealtogether.

2.Method

We follow the definitions of WF and WS as in theGlobal Water Footprint Standard developed by theWater Footprint Network (Hoekstra et al 2011). TheWF, as a multi-dimensional measure of direct andindirect freshwater use, enables to analyse the linkbetween human consumption and the appropriationof water. The consumptive WF of producing a cropincludes a green and blue component, referring toconsumption of rainfall and irrigation water, respec-tively, thus enabling the broadening of perspective onwater resources use as proposed by Falkenmark andRockström (2004). The consumptive WF is distin-guished from the degradative WF, the so-called greyWF, which represents the volume of water required toassimilate pollutants entering freshwater bodies. Inthe current study we focus on the consumptive WF,distinguishing between the green and bluecomponent.

As a starting point we took the consumptiveWF ofUK consumption as was estimated by Hoekstra andMekonnen (2012), with which we got a matrix show-ing the WF of UK consumption per consumptioncategory specified by country of origin and in terms ofblue and green components, in the form of an averagefor the period 1996–2005. This work has been basedon data on food consumption from FAOSTAT(FAO 2015) and international trade in agricultural andindustrial products from the Statistics for Interna-tional Trade Analysis from the International TradeCentre (ITC 2007). For agricultural goods,

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consumption and imports are specified per crop andanimal product, measured in terms of kilogram peryear. Industrial goods form one category as a whole,with consumption and importsmeasured inmonetaryunits. In the current study we traced the origin of pro-ducts down to a 5×5 arc minute grid level and map-ped the related water consumption at that level. Forimported crops and crop products, we traced the ori-gin based on the production pattern per crop percountry. We mapped the WF per crop per origincountry, based on the ratio of the WF of the importedcrop to the total WF of the crop production in the ori-gin country. Per origin country, we multiplied thisratio with the 5×5 arc minute resolution map of theWF of the crop under consideration in the origincountry obtained from Mekonnen and Hoekstra(2011a). The WFs of crop production were estimatedby simulating the daily soil water balance and evapo-transpiration of green and blue water over the growingseason, thereby specifying the WFs by colour and intime (Mekonnen and Hoekstra 2011a). We also tracedthe origin of feed eaten by animals raised in the UK byaccounting for feed crop imports while we traced theorigin of the feed behind the live animals and animalproducts imported to the UK by assuming that thoseanimals are fed with local crops in the origin countriesand by tracing where those feed crops are produced inthe origin countries. For imported live animals andanimal products, we mapped the feed-related WF ofthese animals and products, per origin country, basedon the ratio of theWF of the imported live animals andanimal products to the total WF of agricultural pro-duction in the origin country. Per origin country, wemultiplied this ratio with the 5×5 arcminute resolu-tionmap of theWFof agriculture in the origin countryobtained from Mekonnen and Hoekstra (2011a). Forimported industrial products, similarly, we mappedtheWF of these products, per origin country, based onthe ratio of theWFof the imported industrial productsto the total WF of industrial production. Per origincountry, we multiplied this ratio with the 5×5 arcminute resolution map of the WF of industry in theorigin country as from Hoekstra and Mekonnen(2012). The WF related to the UK’s domestic watersupply at 5×5 arc minute resolution was obtainedfromHoekstra andMekonnen (2012).

We estimate where the UK’s global blueWF is sus-tainable and where unsustainable by checking for eachgrid cell with a UK-consumption related blue WFwhat is the blue WS level in that grid cell. We char-acterize the UK’s blue WF in a particular grid cell as‘unsustainable’when the annual averagemonthly blueWS in that grid cell exceeds 1 (because in such caseenvironmental flow requirements are not fulfilled).We computed the annual average monthly blueWS intheworld at 30×30 arcminute resolution level, usingdata of Hoekstra and Mekonnen (2012) for the ten-year period 1996–2005 (Mekonnen and Hoek-stra 2016), and downscaled these data to 5×5 arc

minute resolution.Monthly blueWS is here defined asthe ratio of the total blue WF in a grid cell in a certainmonth to the maximum sustainable blue WF in thatgrid cell in that month (Hoekstra et al 2011, Hoekstraet al 2012). The maximum sustainable blue WF in agrid cell represents blue water availability and is calcu-lated as the sumof the runoff generated within the gridcell plus the runoff generated in all upstream grid cellsminus the environmental flow requirement andminus the blue WF in upstream grid cells. Monthlyenvironmental flow requirements were assumed at80% of monthly natural runoff, following Richter et al(2012). Annual average monthly blue WS per grid cellwas estimated by averaging the monthly scarcityvalues. Blue WS is called ‘low’ when in a grid cellWS<1, ‘moderate’ when 1�WS�1.5, significantwhen 1.5<WS�2 and ‘severe’whenWS>2.

We estimate the fraction of the consumptive WFof the UK’s direct and indirect crop consumption(including both food and feed crops) that is efficient byquantifying, per grid cell, the percentage of the WF ofUK consumption that meets crop-specific WF bench-mark levels. Per crop, we take as a benchmark level theWF (in m3 ton−1) below which 25% of global produc-tion takes place, taking the values fromMekonnen andHoekstra (2014b). These benchmark levels are reason-ably achievable under all climates, as analysed byMekonnen and Hoekstra (2014b). Yields are rathersensitive to climate, but WFs of crops per unit ofweight are much less sensitive to climate, as shown inMekonnen and Hoekstra (2011a). We characterize theWF related to production of crops for UK consump-tion within a grid cell as ‘efficient’ when at least half ofthat WF is below benchmark levels, and ‘inefficient’when that is not the case. We calculate potential watersavings per grid cell, both the green and bluewater sav-ings, by considering the reduced consumptive WFwhen we reduce those WFs that are beyond bench-mark levels down to the benchmark level. We assumethat the green–blue ratio in the water saving, per cropand per grid cell, is proportional to the green-blueratio in the currentWFof that crop in the grid cell.

3. Results

3.1. Sustainability of theUK’s globalWFWe find that 49%of theUK’s global blueWF is locatedin places where the blue WF exceeds the maximumsustainable blue WF (figure 1). About 55% of theunsustainable part of theUK’s blueWF is located in sixcountries: Spain (14%), USA (11%), Pakistan (10%),India (7%), Iran (6%), and South Africa (6%). Next onthis list come France, Israel and Egypt. These countriescan be considered as the hotspots of concern from theUK consumer perspective, because the UK’s economysignificantly relies on the water resources in thesecountries while the water consumption in the specific

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regions within those countries where export productsfor theUK are produced is not sustainable.

In each hotspot we can identify specific productsthat most significantly contribute to the unsustainablewater use. In Spain these products include rice(responsible for 15% of the UK’s unsustainable blueWF in the country), oranges (13%), olives (12%),mandarins (8%), apricots (8%) and grapes (5%). Thebiggest water problems occur in the southern part ofthe country, in the Guadiana and Guadalquivir riverbasins (Cazcarro et al 2015). In the USA, the criticalproducts are rice (26%), grapes (13%), almonds (10%)and industrial products (10%). Almonds are mainlygrown in California, and rank highest on the list oflarge water consumers in that state, after feed cropsand before residential areas (Fulton et al 2012). WhileCalifornia, together with Spain the world’s mostimportant almond producer, suffers great WS, con-sumption of almonds in the UK is on the rise, thusindirectly contributing to the worsening of the WS inthe source regions. This increasingly results in a publicdebate about the link between consumption and WS(Buchanan et al 2015, Westervelt 2015). In Pakistan,the critical products are sugarcane (responsible for65% of the UK’s unsustainable blue WF in the coun-try), rice (24%) and dry beans (6%). Both sugarcaneand rice production are main contributors to waterstress in the Indus basin, with 212 million peoplefacing severeWSduring eightmonths a year (Hoekstraet al 2012) and widespread groundwater depletion(Qureshi et al 2010, Karimi et al 2013). In India, thecritical products are rice (25%), sugarcane (18%), tea(14%), castor beans (8%), cotton products (6%),groundnuts (5%), rubber (4%) and industrial pro-ducts (9%). In Iran there are just two critical products:dates (63%) and pistachios (33%). The country usesvery substantial amounts of its highly scarce waterresources in its southern provinces for producingthese products for export (Arabi et al 2012). The

critical products in South Africa are citrus fruits (oran-ges, tangerines, mandarins), apples, grapes, apricots,tea, sugarcane and avocados. In France the critical pro-ducts are maize, animal products and industrial pro-ducts, which is problematic for instance in the basinsof the Loire, Seine, Garonne and Scheldt, which allexperiencemoderate to severeWS at least onemonth ayear (Ercin et al 2013). The critical products in Israel,still from the UK import perspective, are papayas,citrus fruits, dates, cherries and potatoes. Water con-sumption in Israel is contentious given the disputesover freshwater the country has with its neighbours,including Jordan and the Palestinians. In Egypt the cri-tical products are sugar beet, oranges, potatoes, sugar-cane and rice, with the major problems in the NileDelta.

3.2. Efficiency of theUK’s globalWF andpotentialwater savingsIn estimating the efficiency of the UK’s global WF wefocus on the footprint related to direct and indirectcrop consumption. The indirect crop consumptionincludes the feed crops behind animal productsconsumed in the UK. Our analysis shows that 50% ofthe global consumptive WF of the UK’s direct andindirect crop consumption is inefficient, whichmeansthat the consumptive WF exceeds the WF benchmarklevel (figure 2). About 37%of the inefficient part of theUK’s consumptive WF is located in six countries:Indonesia (7%), Ghana (7%), India (7%), Brazil (6%),Spain (5%), andArgentina (5%).

The global consumptiveWF of the UK’s direct andindirect crop consumption can be reduced by 17% iftheWF of imported food products at the places of pro-duction is lowered to benchmark levels. About 90% ofthe resultant water saving is green water, while theremainder is blue water. About 28% of the reductionin the UK’s consumptive WF is located in just threecountries (Indonesia, Ghana, India); another 20% of

Figure 1.The sustainable (green) and unsustainable (yellow to red) parts of the global bluewater footprint of overall UK consumption,with an indication of critical products that significantly contribute to theUK’s water footprint in some hotspot areas.

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the reduction is located in yet five other countries(Spain, Brazil, Nigeria, Malaysia, Cameroon). Percountry, the analysis shows which crops are producedrelatively inefficient (with WFs beyond the bench-mark), so that we also knowwhich crops aremost pro-mising in terms of water saving potential. InIndonesia, the greatest green water saving potential,insofar relevant for UK consumer products, is in thecultivation of rubber, coffee, tea and palm oil, whilethe largest blue water saving potential is in the case ofpepper and sugarcane. In Ghana, the most importantpotential green water saving, again insofar relevant forUK consumer products, is in cocoa production, whilethe largest potential blue water saving is in sweet pota-toes. In India, the largest green water savings in rela-tion to products exported to the UK can be achievedfor dry beans, groundnuts, rice, cotton, pepper andwalnuts, and the largest blue water savings in thegrowth of rice, sugarcane, cotton and groundnuts.

The blue WF of the UK’s direct and indirect cropconsumption is shown in figure 3, showing where theWF is efficient and inefficient (relative to crop WFbenchmarks). We find that, by lowering overall con-sumptive WFs to benchmark levels, the global blueWF of UK crop consumption could be reduced by19%. About 62% of the reduction in the UK’s blueWFis located in five countries (Pakistan, Iran, Spain, USAand Egypt), in all of which UK has a substantial unsus-tainable blue WF. This is a very important finding,because it implies that most blue water saving poten-tial is in five of the countries that were identified ashotspots from the UK consumption perspective(figure 1). The largest impact can be achieved in Paki-stan, through increasing the water productivity insugarcane and rice. Next biggest blue water saving canbe obtained in Iran, mainly by improving dates andpistachios cultivation. The potential blue water savingin Spain in relation to crops exported to the UK is

Figure 2.The efficient (green) and inefficient (yellow to red) parts of the global consumptive water footprint of theUK’s direct andindirect crop consumption, with an indication of crops forwhichwater productivity can be substantially increased and throughwhichwater footprints can thus be reduced.

Figure 3.The efficient (green) and inefficient (yellow to red) parts of the global bluewater footprint of theUK’s direct and indirectcrop consumption, with an indication of crops forwhichwater productivity can be substantially increased and throughwhich bluewater footprints can thus be reduced.

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mostly in the cultivation of rice, apricots, olives, grapesand oranges. In the USA, the relevant crops are rice,grapes, almonds, apricots and apples, and in Egyptthese are sugar beets, potatoes, oranges, sugarcane,rice, and cotton.

4.Discussion

This is the first study to trace andmap the globalWF ofa national population at such high level of detail, cropby crop and at high spatial resolution level. The datawe present are rough estimates, given the uncertaintiesin the underlying trade data and the assumptions wemade. We traced the origin of imported crops basedon the production pattern per crop per country,assuming proportionality between production forexport and production for domestic consumption pergrid cell. In reality it may be the case that the UKsources a crop from a specific region within a countrythat is specialised on producing for export to the UK,while other production regions within the countryproduce for local markets or for export to othercountries. Such information, however, is not available,so that our assumption is reasonable for a first globalassessment. We have identified hotspots and criticalproducts per hotspot that deserve further study.Relevant questions are for instance: which majorcompanies are involved in the trade, are the supplychains sufficiently transparent to establish the precisesource areas or even farms of the products exported tothe UK, and what is currently done and whatstakeholders are involved in addressing local sustain-ability and efficiency of water use?

Our estimated potential water savings in thesource areas of the UK’s consumer goods are roughestimates as well. We assume that reducingWFs downto benchmark levels will generally be largely achievedthrough increases in yields, and to a much smallerextent through reduction in evapotranspiration(Mekonnen and Hoekstra 2011a, Chukalla et al 2015).Yield increases and accompanied water productivityincreases can be substantial in many parts of the world(Foley et al 2011, Brauman et al 2013). With yieldincreases, green and blue WFs will be reduced pro-portionally to their original size, hence our assump-tion that the green–blue ratio remains the same whenreducing WF down to benchmark levels. If WFs arereduced through reduction in evapotranspiration (e.g.by reducing soil water evaporation of irrigationwater),our approach becomes questionable. In that case—byassuming that green and blue water are equally saved(proportionally)—we make a conservative estimate ofbluewater saving.

In a global study, Mekonnen and Hoekstra(2014b) found that if we would reduce the con-sumptive WF of crop production everywhere in theworld to the level of the best 25th percentile of currentglobal production, global water saving in crop

production would be 39% compared to the referencewater consumption. The 39% is thus a global referencefor the potential saving by moving down to bench-mark levels. The potential water saving of 17% that wefound for UK consumption is relatively small com-pared to this global number, which relates to the factthat—as an average over all crop and animal productsconsumed by UK citizens—the WF per unit of thefood consumed in the UK is relatively low comparedto the global average, with relatively less potential forsaving.

The choice in the current study to evaluate wateruse efficiency per crop based on the WF benchmarksset by the best 25% of global production is subject todebate. It may be argued that it would be better to usedifferent benchmark levels for different types of cli-mate. According to Zwart et al (2010), highest levels ofwater productivity (smallestWFs per kg of crop) are tobe expected in temperate climates with high precipita-tion. However, Mekonnen and Hoekstra (2014b)argue that, although climatic factors are important indetermining evapotranspiration from crop fields andyields, the consumptive WF of crops in m3 ton−1 islargely determined by agricultural management ratherthan by the climate under which the crop is grown. Alarge increase in crop yields, without an increase oreven with a decrease in water use, is achievable formost crops across the different climate regions of theworld through proper nutrient, water and soil man-agement (Mueller et al 2012). Mekonnen and Hoek-stra (2014b) show that even water productivities set bythe best 10th percentile of global crop production canbe achieved irrespective of climate. Therefore, usingthe WF benchmarks set by the best 25th percentile ofglobal production is realistic, but indeed efforts toachieve these levels will vary from region to region.WFs in m3 ton−1 can be reduced by reducing evapo-transpiration (for example through better irrigationtechniques, a deficit irrigation strategy, and mulch-ing), increasing yields (e.g. through better nutrient andsoil management and pest control), or a combinationof both (Chukalla et al 2015).

5. Conclusion

‘Importedwater risk’ to a national economy aswe haveillustrated for the UK is what ‘supply-chain water risk’is for businesses. While the latter type of risk isreceiving an increasing amount of attention recently(Sarni 2011, Larson et al 2012), the importedwater riskfor national economies as a whole is not appropriatelyappreciated by most national governments. Our studyshows that half of the WF of the UK’s consumption islocated in places where water use is not sustainable.This implies the risk that exports from these regions inthe future will decline or become impossible alto-gether. Imported water risks as we have shown for theUK are likely to increase, due to increasing water

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demands in the source regions that will result fromgrowing populations and changing consumption pat-terns (Ercin and Hoekstra 2014), while climate changemay affect water supply in the source regions(Orlowsky et al 2014). Importing goods that areproduced with water in locations where water is beingoverexploited (with WFs exceeding maximum sus-tainable levels) bears a risk.WhereWFs are unnecessa-rily large (with WFs per unit of production exceedingbenchmark levels), there is potential for water savingand reduction ofWS.

There are basically four risk mitigation strategiesthat national governments may pursue: (1) move to agreater degree of food self-sufficiency; (2) diversify theimport of water-intensive commodities, preferablytargeting water-abundant countries; (3) reduce thereliance on import of water-intensive commoditiesfrom regions where water use is unsustainable andwhere little opportunities exist to improve that; and(4) collaborate internationally with source countrieswith unsustainable water use where opportunitiesexist to increase water productivity and thusreduceWFs.

With respect to the first strategy—greater food self-sufficiency—the results of the current study can feedinto the on-going discussion within the UK on how toincrease food security, against the trend in the past fewdecades of increasing food imports and decreasing self-sufficiency (DEFRA 2008, 2009a, 2009b, Hubbard andHubbard 2013). Crop production in theUK is relativelyefficient and sustainable from a water resources per-spective, so that increasing food self-sufficiency seemsfeasible. Food self-sufficiency could further beincreased by reducing the consumption of meat anddairy and by reducing food waste, thus reducing theland, water and carbon footprints of the UK’s con-sumption (Chapagain and James 2011, Foley et al 2011,Kummu et al2012,Vanham et al2013,West et al 2014).

The second strategy—diversifying imports—isagainst another historical trend, the specialisation ofregions in single crops that supply a large share of theworld market. For instance, in the period 2001–2012,44% of the dates imported by the UK came from Iran,28% of the imported oranges came from Spain and22% from South Africa, 64% of the imported almondscame from the USA (mainly California), and 71% ofthe imported soybean came fromBrazil (FAO2015).

The third strategy requires a reconsideration ofimport of water-intensive commodities from theregions that are most severely water stressed. Onemaywonder whether it is wise to import crops like sugarcane from the scarce Indus basin in Pakistan or sugarbeets and potatoes from the highly water-scarce NileDelta in Egypt. These questions become even morepressing given the fact that the UK can produce sugarand potatoes perfectly well within its own territory.

The fourth strategy is international collaborationon sustainable water use. Since the export of a crop

from a country to specifically the UK is always rela-tively small, given that the largest fraction of crops isgenerally for the domestic market or export to othercountries, one cannot expect that improving the pro-duction of only those crops that are actually exportedto the UK will make a big impact in the source areas asa whole. We identified five highly water-scarce coun-tries where the UK economy significantly relies on butwhich have relatively great blue water saving poten-tials. If UK wants to secure its supplies from thesecountries, it does not help if it focuses only on increas-ing water productivity at the farms fromwhich it sour-ces most of its imports. What is really needed is overallsustainable water use in the source regions of its mostimportant water-intensive import products. There-fore, theUK government could aim toworkwith othercountries on internationally shared targets on sustain-able water use. The Sustainable Development Goals(SDGs) of the United Nations offer a good startingpoint for intensified international collaboration onsustainable and efficient water use. The fourth targetof the SDG onwater is to ‘substantially increase water-use efficiency across all sectors and ensure sustainablewithdrawals and supply of freshwater to address WSand substantially reduce the number of people suffer-ing fromWS’. This is a rather vague target and requiresoperationalization in quantitative terms per country,but at least offers a good basis for further cooperationandmore specific target setting.

The first three strategies mentioned above requireflexibility in directly or indirectly influencing interna-tional trade flows. International free trade agreementsthat will reduce this flexibility or make it impossiblealtogether to implementmeasures that discourage cer-tain unsustainable trade flows and/or favour sustain-able trade flows will reduce the UK’s potential tomitigate its importedwater risk.

Acknowledgment

This study was partially developed within the frame-work of the Panta Rhei Research Initiative of theInternational Association of HydrologicalSciences (IAHS).

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