Water reuse to free up freshwater for higher?value use and increase climate resilience and water productivity

The impact of climate change on the availability water affects all types land use and sectors. This complexity calls for integrated resources management negotiations between sectors most important, cost-effective, productive allocation where it is a limited resource. reflection paper shows examples adaptation efforts to scarcity at scale gains in productivity can be derived from inter-sectoral reuse wastewater–freshwater swaps, complementing other coping strategies (water savings, long-distance transfer, desalination). Wastewater treatment offers opportunities across scales as allows, example, donor regions compensated with reclaimed release freshwater higher-value use, increasing overall economic this way. In such farmers are higher volumes exchange quality. (i) expand traditional (agricultural) concept (ii) significantly increase system level. While rural–urban reallocation help mitigate impacts change, compensating remains reasons discussed paper. L'impact du changement climatique sur la disponibilité de l'eau affecte tous les d'utilisation des terres et secteurs. Cette complexité appelle une gestion intégrée ressources en eau (GIRE) négociations entre secteurs l'allocation plus importante, rentable, là où celle-ci est ressource limitée. Ce document réflexion montre exemples d'efforts d'adaptation à rareté grande échelle productivité peuvent être dérivés réutilisation intersectorielle échanges d'eaux usées d'eau douce, complément d'autres stratégies (économies d'eau, transfert longue distance, dessalement). Le traitement eaux pour offre opportunités particulières car il permet aux régions donatrices d'être compensées par récupérée libération douce utilisation valeur, augmentant ainsi économique globale l'eau. Dans ces agriculteurs sont indemnisés avec élevés échange d'une meilleure qualité. La pour: i) étendre le traditionnel [agricole]; ii) augmenter considérablement au niveau système. Alors que réallocation zones rurales urbaines peut aider atténuer climatique, l'indemnisation reste encore limitée raisons évoquées dans document. Floods droughts detrimental terms people affected natural disasters (Centre Research Epidemiology Disasters (CRED) UN Office Disaster Risk Reduction (UNDRR), 2020), there significant concerns that will frequency or severity drought events future (Cook al., 2020). affect quantity required irrigation food security, environmental flows, hydropower generation, or, depending their duration, result migration, poverty, negative short- long-term health effects, which could ultimately lead social segregation grounds access (Nicolas & Alisher, 2017). case Middle East, South Africa, India, term “water apartheid” increasingly used flag low-income households suffer when becomes scarce expensive (Jegede Shikwambane, 2021; Kookana According Sadoff al. (2015), countries vulnerable gross domestic product losses due eastern southern America, Southeast Asia. Although agricultural literature extensive, only recent cases, Cape Town approaching Day Zero,11 https://en.wikipedia.org/wiki/Cape_Town_water_crisis have raised awareness challenges urban areas society large. McDonald (2014) estimated water-stressed large cities represent $4.8 trillion activity, any change-triggered implications. Drought-induced cuts Barcelona region, resulted an loss €1.6 billion 2007/2008 (Martin-Ortega 2012). With population growth demands, production also must increase. Flörke (2018) about 40% world's largest likely competition crop irrigation—a scenario considered unlikely decade ago (Molle Berkoff, 2006). progressing (IWRM) improve allocations, efficiency, address possible (Smith Clausen, 2015). Typical ways resilience range conservation measures seawater desalination, transfers, reclamation (Garrick 2019; Jones Multipronged approaches appear safest bet although they not without (Box 1). part Spain, Tajo–Segura inter-basin transfer (or Tagus–Segura Aqueduct, TSA) has been main source three Spanish provinces Murcia, Alicante, Almería since 1979, addition providing tourism consumption. Consisting over 40,000 ha, 286-km conveyance infrastructure turned semi-arid region into Europe's vegetable garden. Estimates suggest led wealth generation amounting US$ 2.9 per year started. success relies combination mechanisms resilience: wastewater reclamation, approximately ratio 4:2:1, improved efficiency. As multipronged approach, region's against increased significantly: Today 100,000 jobs directly indirectly related sector another 200,000 supply pertinent resources. However, continues experience tensions recipient basins, first calling compensation given its own sensitivity. Moreover, TSA was designed late 1960s, adjustments based more predictions needed, keeping mind reliance desalination increases carbon footprint (Martin-Gorriz Morote Aside sourcing additional water, option by generating multiple benefits same unit intermediate treatment. Commonly referenced technical excellence include potable Singapore Namibia, supported business model requires lack alternatives, reliable technology, positive public perceptions (Lazarova 2013). Significantly larger irrigation. area treated best totals few hundred thousand hectares (Jiménez Asano, 2008), Thebo (2017) estimate globally 30 million ha irrigated croplands already benefiting (often untreated, but diluted) wastewater. potential much 42 looking undiluted (Qadir Where scarce, might buffer replace (Food Agriculture Organization United Nations [FAO], 2010; Heinz 2011; Otoo Drechsel, 2018). Using empirical highlights importance change-induced shortages, particular focus freshwater–wastewater encourages extension beyond plot-based roots (Scheierling Tréguer, 2016; Wichelns, 2014). common geographical (and economic) limitations both force utilities investigate originally stored production. Given quantities involved farming perception agriculture relatively inefficient, even small improvements make available uses 2016). suggested 10% improvement efficiency free up enough 80% high-water-conflict sub-basins. Changing cropping patterns investing water-saving technologies tackle Iran, cut half (Salami 2009). 20% enough, options, off-farm. Town, peri-urban were able donate 10 Mm3 (million cubic metres) reservoirs city prevent Zero. Such donations remain, however, exception than rule unless contractually agreed upon. gain nature value use. recycled, created amount water. Reuse thus opens new doors definitions productivity” guide basin towards savings within hydrologic systems. one user option, supporting, cascades salinity Reallocation expands IWRM perspective (Figure one-directional reallocations criticized missing compensations Molle 2006), swaps offer better deal multiply (value) gained product(s) volume invested. Source: Authors Figure 1 simplicity conventional “crop drop” indicator extended capture generated considering far direct indirect (downstream) jobs, welfare, environment (Giordano Scheierling assessments (Heinz see below) dynamic values may vary time, space, (type volumes), acceptance (Hussain 2007). Rural–urban broaden scope using return flows downstream significantly. On hand, actually happen upstream, other, flow gets farms. words, rural handing rights offered cover resulting gaps 2). purchasing power, downstream–upstream pumping requirement either covered ? Augmenting supply: declining groundwater levels, response exploit surface seek further away. less abundant, transfers often demand-driven easily conflicts tensions, seen Chennai, local residents blocking roads laying siege tanker lorries protect (Varadhan, 2019). A similar resistance industrial needs reported earlier Uttar Pradesh (Chaudhary, To avoid these situations, Other sources options towing icebergs polar ice caps tapping hosted aquifers beneath seafloor (UN-Water, investments aquifer extractions municipal budget, pay off compared costs “Day Zero” aftermath. cycles: Mexico City plans augment share 160–190 Mm3/year (wastewater)-saturated Mezquital back (Comisión Nacional del Agua, Valley well known enormous (Jiménez, 2008). taking advantage soil recharge largely acceptable quality Chávez, 2004). Tapping would cost-effective alternative options. From perspective, then get circulated potentially cycles swaps: many cases abstraction swap arrangement cede assured supplies wastewater, which, kind treatment, contain valuable nutrients (FAO, 2010). usually sources, substantially what release, making win-win parties long place. excellent example lower (Otoo Water sense is, cannot afford itself. represents viable sufficient incentives agree under competing political pressure place (water) losing end, benefit compensate allocations very supply, crucial variability. following present Mashhad Plain Llobregat Delta near Barcelona, Durango Mexico. chosen deficits level urbanization and/or adaptation. Iran study. faced deficit years, made necessary approach highlands rights. need too, incentive 1.2 times initially opposed plan (Yazdi, 2011), 2006, started annually 21 two dams 25 fixed contract rights-holding Regional Company (Danso power steered negotiations, opposite possible, Chakera, Pakistan, strongly preferred (untreated) instead (the temporarily nutrient-poor) (Hanjra shortfall Iranian arrived farm good had promised, capacity development safe Global Intelligence (GWI), modified Spain contrast continuous Mashhad, planned longer-lasting normally experienced. situation happened 2007/2008, severe (see above), catalysed desalination. possibility investment secure farmers' 57 m3 high-quality day (18.8 Mm3/year) during prolonged periods needed block intrusion. remained flexible allow needed. fact, view last resort no longer permitted, reliable, exceeds (Drechsel treats nearly 100% reused different applications, irrigation, parks gardens, mining. concern because Guadiana aquifer, Durango, contaminated overexploited, 35 At state level, 85% total consumption 2009), underlines sector. 2:1 wastewater-to-freshwater municipality Irrigation District 052 facilitated support congress. concession titles 17 Mm3, provides 34 district comprises 13,455 managed 3,000 farmers, consuming roughly 137 (ca. 10,000 hectare) (Subdirección General Infraestructura Hidroagrícola (SGIH), advantages multiple: Guadalupe Victoria dam provide 30% demand, while cease overexploited; receive good-quality cost energy saved reduced aquifer; irrigators crops, enabled yield (up 30%) corn, alfalfa, oats, saving 50% fertilizer building drinking plant newly sourced (Bnamericas, 2021). beginning negotiation process, socialization scheme users aware Additionally, program implemented producers requirements fraction still constitutes important pillar mitigating effects For period months (2010–2012), 2,000 otherwise produced crops. These show that, mitigation strategies, combining reallocation, recycling useful. role context, vis-à-vis transfer. intensifying uses, rapidly escalating incremental supplies, rational growing amounts (treated) required. opportunity allocate how distinct volume, after serving city, create agronomic value. But (de facto perceived as) foregone freshwater, struggle accept it. allows nutrient-rich source, economically socially purposes. benefits, shown, Delta, catalysing expect, replenishing preventing intrusion, maintaining flows. That financially outweigh including demonstrated (2011). authors showed modest community yields incomes received released, benefitted through high extraction, released valued proxy current price consumers' willingness pay, scarcity. detailed cost–benefit analysis carried out suggests years drought, added net benefit) €7 million. calculated 0.22 €/m3, reached 1.11 €/m3. What, counts withstand economy be, just year, multitudes extra conveyance. productivity, factor 41 comparing sites plants 2010), dimensions farm-based interventions Molden CGIAR Program Water, Land Ecosystems (WLE) OneCGIAR Initiative Resilient Cities. Thanks go Susanne Scheierling, formerly World Bank, her assistance thinking box. contributes UNU-INWEH’s project unconventional Manzoor Qadir gratefully appreciates Government Canada UNU-INWEH Affairs Canada. Data domain