Editing IPCC:AR6/WGIII/Chapter-3 (section)

=== 3.7.3 Water ===

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Water isrelevant to SDG 6 (clean water and sanitation), SDG 15 (life on land ), and SDG Targets 12.4 and 3.9 (water pollution and health). This section discusses water quantity, water quality, and water-related extremes. See [[#3.7.5|Section 3.7.5]] for water-related health effects.

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==== 3.7.3.1 Benefits of Avoided Climate Impacts Along Mitigation Pathways ====

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Global precipitation, evapotranspiration, runoff and water availability increase with warming ( [[#Hanasaki--2013|Hanasaki et al. 2013]] ; [[#Greve--2018|Greve et al. 2018]] ) (AR6 WGII Chapter 4). Climate change also affects the occurrence of and exposure to hydrological extremes ( ''high confidence'' ) ( [[#Arnell--2014|Arnell and Lloyd-Hughes 2014]] ; [[#Asadieh--2017|Asadieh and Krakauer 2017]] ; [[#Dottori--2018|Dottori et al. 2018]] ; [[#Naumann--2018|Naumann et al. 2018]] ; [[#IPCC--2019a|IPCC 2019a]] ; [[#Do--2020|Do et al. 2020]] ) (AR6 WGII Chapter 4). Climate models project increases in precipitation intensity ( ''high confidence'' ), local flooding ( ''medium confidence'' ), and drought risk ( ''very high confidence'' ) ( [[#Arnell--2014|Arnell and Lloyd-Hughes 2014]] ; [[#Asadieh--2017|Asadieh and Krakauer 2017]] ; [[#Dottori--2018|Dottori et al. 2018]] ; [[#IPCC--2019a|IPCC 2019a]] ) (AR6 WGII Chapter 4).

The effect of climate change on water availability and hydrological extremes varies by region ( ''high confidence'' ) due to differences in the spatial patterns of projected precipitation changes ( [[#Hanasaki--2013|Hanasaki et al. 2013]] ; [[#Schewe--2014|Schewe et al. 2014]] ; [[#Schlosser--2014|Schlosser et al. 2014]] ; [[#Asadieh--2017|Asadieh and Krakauer 2017]] ; [[#Dottori--2018|Dottori et al. 2018]] ; [[#Naumann--2018|Naumann et al. 2018]] ; [[#Koutroulis--2019|Koutroulis et al. 2019]] ) (AR6 WGII Chapter 4). Global exposure to water stress is projected to increase with increased warming, but increases will not occur in all regions ( [[#Hanasaki--2013|Hanasaki et al. 2013]] ; [[#Schewe--2014|Schewe et al. 2014]] ; [[#Arnell--2014|Arnell and Lloyd-Hughes 2014]] ; [[#Gosling--2016|Gosling and Arnell 2016]] ; [[#IPCC--2019a|IPCC 2019a]] ).

Limiting warming could reduce water-related risks ( ''high confidence'' ) ( [[#O’Neill--2017b|O’Neill et al. 2017b]] ; [[#Byers--2018|Byers et al. 2018]] ; [[#Hurlbert--2019|Hurlbert et al. 2019]] ) (AR6 WGII Chapter 4) and the population exposed to increased water stress ( [[#Hanasaki--2013|Hanasaki et al. 2013]] ; [[#Arnell--2014|Arnell and Lloyd-Hughes 2014]] ; [[#Schewe--2014|Schewe et al. 2014]] ; [[#Gosling--2016|Gosling and Arnell 2016]] ; [[#IPCC--2019a|IPCC 2019a]] ).

The effect of climate change on water depends on the climate model, the hydrological model, and the metric ( ''high confidence'' ) stress [[#Hanasaki--2013|Hanasaki et al. (2013)]] ; [[#Arnell--2014|Arnell and Lloyd-Hughes (2014)]] ; [[#Schewe--2014|Schewe et al. (2014)]] ; [[#Schlosser--2014|Schlosser et al. (2014)]] ; [[#Gosling--2016|Gosling and Arnell (2016)]] ; [[#IPCC--2019a|IPCC (2019a)]] .

However, the effect of socio-economic development could be larger than the effect of climate change ( ''high confidence'' ) ( [[#Arnell--2014|Arnell and Lloyd-Hughes 2014]] ; [[#Schlosser--2014|Schlosser et al. 2014]] ; [[#Graham--2020|Graham et al. 2020]] ).

Climate change can also affect water quality (both thermal and chemical) ( [[#Liu--2017|Liu et al. 2017]] ), leading to increases in stream temperature and nitrogen loading in rivers ( [[#Ballard--2019|Ballard et al. 2019]] ).

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==== 3.7.3.2 Implications of Mitigation Efforts Along Pathways ====

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The effects of mitigation on water demand depends on the mitigation technologies deployed ( ''high confidence'' ) ( [[#Chaturvedi--2013a|Chaturvedi et al. 2013a]] ,b; [[#Hanasaki--2013|Hanasaki et al. 2013]] ; [[#Kyle--2013|Kyle et al. 2013]] ; [[#Hejazi--2014|Hejazi et al. 2014]] ; [[#Bonsch--2016|Bonsch et al. 2016]] ; [[#Jakob--2016|Jakob and Steckel 2016]] ; [[#Mouratiadou--2016|Mouratiadou et al. 2016]] ; [[#Fujimori--2017|Fujimori et al. 2017]] ; [[#Maïzi--2017|Maïzi et al. 2017]] ; [[#Bijl--2018|Bijl et al. 2018]] ; [[#Cui--2018|Cui et al. 2018]] ; [[#Graham--2018|Graham et al. 2018]] ; [[#Parkinson--2019|Parkinson et al. 2019]] ). Some mitigation options could increase water consumption (volume removed and not returned) while decreasing withdrawals (total volume of water removed, some of which may be returned) ( [[#Kyle--2013|Kyle et al. 2013]] ; [[#Fricko--2016|Fricko et al. 2016]] ; [[#Mouratiadou--2016|Mouratiadou et al. 2016]] ; [[#Parkinson--2019|Parkinson et al. 2019]] ). Bioenergy and BECCS can increase water withdrawals and water consumption ( ''high confidence'' ) ( [[#Chaturvedi--2013a|Chaturvedi et al. 2013a]] ; [[#Kyle--2013|Kyle et al. 2013]] ; [[#Hejazi--2014|Hejazi et al. 2014]] ; [[#Bonsch--2016|Bonsch et al. 2016]] ; [[#Jakob--2016|Jakob and Steckel 2016]] ; [[#Mouratiadou--2016|Mouratiadou et al. 2016]] ; [[#Fujimori--2017|Fujimori et al. 2017]] ; [[#Maïzi--2017|Maïzi et al. 2017]] ; [[#Séférian--2018|Séférian et al. 2018]] ; [[#Yamagata--2018|Yamagata et al. 2018]] ; [[#Parkinson--2019|Parkinson et al. 2019]] ) (AR6 WGII Chapter 4). DACCS ( [[#Fuhrman--2020|Fuhrman et al. 2020]] ) and CCS ( [[#Kyle--2013|Kyle et al. 2013]] ; [[#Fujimori--2017|Fujimori et al. 2017]] ) could increase water demand; however, the implications of CCS depend on the cooling technology and when capture occurs ( [[#Magneschi--2017|Magneschi et al. 2017]] ; [[#Maïzi--2017|Maïzi et al. 2017]] ; [[#Giannaris--2020|Giannaris et al. 2020]] ). Demand-side mitigation (e.g., dietary change, reduced food waste, reduced energy demand) can reduce water demand ( [[#Bajželj--2014|Bajželj et al. 2014]] ; Aleksandrowicz et al. 2016; [[#Green--2018|Green et al. 2018]] ; [[#Springmann--2018|Springmann et al. 2018]] ). Introducing specific measures (e.g., environmental flow requirements, improved efficiency, priority rules) can reduce water withdrawals ( [[#Bertram--2018|Bertram et al. 2018]] ; [[#Bijl--2018|Bijl et al. 2018]] ; [[#Parkinson--2019|Parkinson et al. 2019]] ).

The effect of mitigation on water quality depends on the mitigation option, its implementation, and the aspect of quality considered ( ''high confidence'' ) ( [[#Ng--2010|Ng et al. 2010]] ; [[#Flörke--2019|Flörke et al. 2019]] ; [[#Sinha--2019|Sinha et al. 2019]] ; [[#Smith--2019|Smith et al. 2019]] ; [[#Fuhrman--2020|Fuhrman et al. 2020]] ; [[#Karlsson--2020|Karlsson et al. 2020]] ; [[#McElwee--2020|McElwee et al. 2020]] ).

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