Editing IPCC:AR6/WGII/Chapter-4 (section)

=== 4.6.3 Adaptation in Energy and Industrial Sectors ===

<div id="h2-37-siblings" class="h2-siblings"></div>

While AR5 ( [[#Arent--2014|Arent et al., 2014]] ) had looked at demand and supply changes in the energy sector due to climate change, none of the AR5 chapters had assessed adaptations in the energy sector per se. A modelling study by [[#van%20Vliet--2016b|van Vliet et al. (2016b)]] demonstrated that increasing the efficiency of hydropower plants by up to 10% could offset the impacts of decreased water availability in most regions by mid-century, under both RCP2.6 and RCP8.5 scenarios ( ''medium confidence'' ). Changing hydropower operation protocol and plant design can be effective adaptation measures, yet may be insufficient to mitigate all future risks related to increased floods and sediment loads ( [[#Lee--2016|Lee et al., 2016]] ).

[[#van%20Vliet--2016b|van Vliet et al. (2016b)]] projected that even a 20% increase in efficiency of thermoelectric power plants might not be enough to offset the risks of water stress by mid-century ( ''medium confidence'' ). Therefore, thermoelectric power plants will need additional adaptation measures such as changes in cooling water sources and alternative cooling technologies ( [[#van%20Vliet--2016c|van Vliet et al., 2016c]] ). In China, many CFPPs in water-scarce North China have adopted air cooling technologies ( [[#Zhang--2016a|]] [[#Zhang--2016|Zhang et al., 2016]] a ). In Europe, wet/dry cooling towers ( [[#Byers--2016|Byers et al., 2016]] ) and seawater cooling ( [[#Behrens--2017|Behrens et al., 2017]] ) have been the preferred options. Overall, freshwater withdrawals for adapted cooling systems under all scenarios are projected to decline by −3% to −63% by 2100 compared to the base year of 2000 ( [[#Fricko--2016|Fricko et al., 2016]] ) ( ''medium confidence'' ).

Diversifying energy portfolios to reduce water-related impacts on the energy sector is another effective adaptation strategy with high mitigation co-benefits. A modelling study from Europe shows that for a 3°C scenario, an energy mix with an 80% share of renewable energy can potentially reduce the overall negative impacts on the energy sector by a factor of 1.5 times or more ( [[#Tobin--2018|Tobin et al., 2018]] ). In addition, hydropower can also play a role in compensating for the intermittency of other renewable energies ( [[#François--2014|François et al., 2014]] ). For example, integrating hydro, solar and wind power in energy generation strategies in the Grand Ethiopian Renaissance Dam can potentially deliver multiple benefits, including decarbonisation, compliance with environmental flow norms and reduce potential conflicts among Nile riparian countries ( [[#Sterl--2021|Sterl et al., 2021]] ). Furthermore, reducing the share of thermoelectric power with solar and wind energy ( [[#Tobin--2018|Tobin et al., 2018]] ; [[#Arango-Aramburo--2019|Arango-Aramburo et al., 2019]] ; [[#Emodi--2019|Emodi et al., 2019]] ) can be synergistic from both climate and water perspectives, as solar and wind energy have lower water footprints ( ''high confidence'' ).

Indigenous Peoples, mountain communities and marginalised minorities often bear the brunt of environmental and social disruptions due to hydropower. As a consequence, hydropower operators face resistance prior to and during construction. Benefit-sharing mechanisms help redistribute some of the gains from hydropower generation to the communities in the immediate vicinity of the project. For instance, sharing of hydropower revenues and profits to fund local infrastructure and pay dividends to local people has been practiced in Nepal and in some countries of the Mekong basin to enhance the social acceptability of hydropower projects ( [[#Balasubramanya--2014|Balasubramanya et al., 2014]] ; [[#Shrestha--2016|Shrestha et al., 2016]] ) ( ''low confidence'' ).

Most water-intensive industries are increasingly facing water stress, making the reuse of water an attractive adaptation strategy (see Box 4.5). For example, Singapore, where the share of industrial water use is projected to grow from 55% in 2016 to 70% in 2060, is increasing its NEWater (highly treated wastewater) supply share from 30% to 55% to meet the growing demand of industrial and cooling activities ( [[#PUB--2016|PUB, 2016]] ). In addition, the mining industry has also adopted water adaptations measures, such as water recycling and reuse; using brackish or saline sources; and working with regional water utilities to reduce water extraction and improve water use efficiency ( [[#Northey--2017|Northey et al., 2017]] ; [[#Odell--2018|Odell et al., 2018]] ).

In summary, energy and industrial sector companies have undertaken several adaptation measures to reduce water stress, with varying effectiveness levels. However, residual risks will remain, especially at higher levels of warming ( ''medium confidence'' ).

<div id="box-4.3" class="h2-container box-container"></div>

'''Box 4.3 | Irrigation as an Adaptation Response'''
<div id="h2-60-siblings" class="h2-siblings"></div>

Irrigation has consistently been used as a crop protection and yield enhancement strategy and has become even more critical in a warming world ( [[#Siebert--2014|Siebert et al., 2014]] ). Approximately 40% of global yields come from irrigated agriculture, with a doubling of irrigated areas over the last 50 years and now constituting around 20% of the total harvested area ( [[#FAO--2018b|FAO, 2018b]] ; [[#Meier--2018|Meier et al., 2018]] ; [[#Rosa--2020b|Rosa et al., 2020b]] ). Thus, irrigation is one of the most frequently applied adaptation responses in agriculture and features centrally in projections of adaptation at all scales. Expansions of irrigated areas over the coming century are projected, leading to shifts from rain-fed to irrigated agriculture in response to climate change ( [[#Malek--2018|Malek and Verburg, 2018]] ; [[#Huang--2019|Huang et al., 2019]] ; [[#Nechifor--2019|Nechifor and Winning, 2019]] ). However, there are regional limitations to this expansion due to renewable water resource limitations, including water quality issues ( [[#Zaveri--2016|Zaveri et al., 2016]] ; [[#Turner--2019|Turner et al., 2019]] ). Depending on the specific spatial, temporal and technological characteristics of irrigation expansion, up to 35% of current rain-fed production could sustainably shift to irrigation with limited negative environmental effects ( [[#Rosa--2020b|Rosa et al., 2020b]] ).

Irrigation increases resilience and productivity relative to rain-fed production by reducing drought and heat stress on crop yields and by lowering ET demand by cooling canopy temperatures ( [[#Siebert--2014|Siebert et al., 2014]] ; [[#Tack--2017|Tack et al., 2017]] ; [[#Li--2018|Li and Troy, 2018]] ; Zaveri and B. Lobell, 2019; [[#Agnolucci--2020|Agnolucci et al., 2020]] ; [[#Rosa--2020b|Rosa et al., 2020b]] ). Large-scale irrigation also affects local and regional climates ( [[#Cook--2020b|Cook et al., 2020b]] ). While cooling effects, including reduction of the extreme heat due to irrigation, have been observed ( [[#Qian--2020|Qian et al., 2020]] ; [[#Thiery--2020|Thiery et al., 2020]] ), increases in humid heat extremes because of irrigation with potentially detrimental health outcomes have also been reported ( [[#Krakauer--2020|Krakauer et al., 2020]] ; [[#Mishra--2020|Mishra et al., 2020]] ). For the heavily irrigated North China Plain, a night-time temperature increase overcompensated daytime cooling effects, leading to an overall warming effect ( [[#Chen--2018|Chen and Jeong, 2018]] ). In addition, modification of rainfall patterns has been linked to irrigation ( [[#Alter--2015|Alter et al., 2015]] ; [[#Kang--2019|Kang and Eltahir, 2019]] ; [[#Mathur--2020|Mathur and AchutaRao, 2020]] ). For example, increases in extreme rainfall in central India in recent decades has been linked to the intensification of irrigated paddy cultivation in northwest India ( [[#Devanand--2019|Devanand et al., 2019]] ).

Different irrigation techniques are associated with significant differences in irrigation water productivity ( [[#Deligios--2019|Deligios et al., 2019]] ), and replacing inefficient systems can reduce average non-beneficial water consumption by up to 76% while maintaining stable crop yields ( [[#Jägermeyr--2015|Jägermeyr et al., 2015]] ). Several adjustments can improve water use efficiency, including extending irrigation intervals, shortening the time of watering crops or reducing the size of the plot being irrigated ( [[#Caretta--2015|Caretta and Börjeson, 2015]] ; [[#da%20Cunha--2015|da Cunha et al., 2015]] ; [[#Dumenu--2016|Dumenu and Obeng, 2016]] ). Deficit irrigation is an important mechanism for improving water productivity ( [[#Zheng--2018|Zheng et al., 2018]] ) and increasing regional crop production under drying conditions ( [[#Malek--2018|Malek and Verburg, 2018]] ). Access to irrigation can also play a role in alleviating poverty, contributing to reducing vulnerability and risks ( [[#Balasubramanya--2020|Balasubramanya and Stifel, 2020]] ). However, the diversity of irrigation-related techniques and the consequent differences in effect and water-use intensity is often underreported ( [[#Vanschoenwinkel--2018|Vanschoenwinkel and Van Passel, 2018]] ).

The use of water-saving technologies like laser levelling, micro-irrigation, efficient pumps and water distribution systems ( [[#Kumar--2016|Kumar et al., 2016]] ); increasing irrigation efficiency ( [[#Wang--2019a|Wang et al., 2019a]] ) through improved agronomic practices ( [[#Kakumanu--2018|Kakumanu et al., 2018]] ) and economic instruments like water trading in developed countries like Australia ( [[#Kirby--2014|Kirby et al., 2014]] ) are known to reduce water application rates and increase yields, and ‘save’ water at the plot level, but may exacerbate basin-scale water scarcity ( [[#van%20der%20Kooij--2013|van der Kooij et al., 2013]] ; [[#Zhou--2021|Zhou et al., 2021]] ).

Asia accounts for 69–73% of the world’s irrigated area. However, irrigation currently plays a relatively minor role in most of Africa, except in the contiguous irrigated area along the Nile basin and North Africa and South Africa ( [[#Meier--2018|Meier et al., 2018]] ). In India, long-term data (1956–1999) on the irrigated area shows that farmers adjust their irrigation investments and crop choices in response to medium-run rainfall variability ( [[#Taraz--2017|Taraz, 2017]] ). da Cunha et al. (2015) report that farmers’ income tends to be higher on irrigated lands in Brazil. In Bangladesh, farmers invest a part of their increased incomes in improving irrigation access ( [[#Delaporte--2018|Delaporte and Maurel, 2018]] ). The severity of drought increases the likelihood of farmers adopting supplementary irrigation in Bangladesh ( [[#Alauddin--2014|Alauddin and Sarker, 2014]] ). In Vietnam, irrigation improvement had the highest positive impact on crop yield among all farm-level adaptive practices ( [[#Ho--2019|Ho and Shimada, 2019]] ). In South Africa, access to irrigation was one of the most important predictors of whether or not farmers would adopt a whole suite of other adaptation responses ( [[#Samuel--2019|Samuel and Sylvia, 2019]] ).

Irrigation is also associated with adverse environmental and socioeconomic outcomes, including groundwater over-abstraction, aquifer salinisation ( [[#Foster--2018|Foster et al., 2018]] ; [[#Pulido-Bosch--2018|Pulido-Bosch et al., 2018]] ; [[#Quan--2019|Quan et al., 2019]] ; [[#Blakeslee--2020|Blakeslee et al., 2020]] ) and land degradation ( [[#Singh--2018|Singh et al., 2018]] ). Further, while irrigation expansion is one of the most commonly proposed adaptation responses, there are limitations to further increases in water use, as many regions are already facing water limitations under current climatic conditions ''(high confidence)'' ( [[#Rockström--2014|Rockström et al., 2014]] ; [[#Steffen--2015|Steffen et al., 2015]] ; [[#Kummu--2016|Kummu et al., 2016]] ).

Projections of the future effectiveness of irrigation indicate a varying degree of effectiveness depending on the region and specific type and combination of approaches used. At the same time, overall residual impacts increase at higher levels of warming ( [[#4.7.1.2|Section 4.7.1.2]] ). Uncertainties in regional climate projections and limitations in the ability of agricultural models to fully represent water resources are important limitations in our understanding of the potential of further irrigation expansion ( [[#4.5.1|Section 4.5.1]] ) ( [[#Greve--2018|Greve et al., 2018]] ).

In light of the volume of irrigated agriculture globally, and the projected increase in water requirements for food production, increasing water productivity and thus improving the ratio of water used per unit of agricultural output is necessary globally to meet agricultural water demand ( [[#4.5.1|Section 4.5.1]] ) ( [[#Jägermeyr--2015|Jägermeyr et al., 2015]] ; [[#Jägermeyr--2017|Jägermeyr et al., 2017]] ). For example, assuming a doubling of global maize production by 2050 increased water productivity could reduce total water consumption compared to the baseline productivity by 20–60% ( [[#Zheng--2018|Zheng et al., 2018]] ). Under economic optimisation assumptions, shifts towards less water-intensive and less climate-sensitive crops would be optimal in terms of water use efficiency and absolute yield increases; however, this could pose risks to food security as production shifts away from main staple crops ( [[#Nechifor--2019|Nechifor and Winning, 2019]] ). Shifting currently rain-fed production areas to irrigation will be an important element in ensuring food security with increasing temperatures, though investment in storage capacities to buffer seasonal water shortage will be essential to ensure negative environmental impacts are minimised ( [[#Rosa--2020b|Rosa et al., 2020b]] ).

<div id="_idContainer075" class="Box_Header-continued"></div>

Box 4.3

<div id="4.6.4" class="h2-container"></div>

<span id="adaptation-in-the-water-sanitation-and-hygiene-sector"></span>