Editing IPCC:AR6/WGII/Chapter-13 (section)

==== 13.2.2.2 Water Resources Management ====

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Planning adaptation to water scarcity has centred on increasing the availability and supply of freshwater through water storage, diversification of sources and water diversion and transfer ( ''high confidence'' ). Reservoirs are costly, have negative environmental impacts and will not be sufficient under higher warming levels in every place ( [[#Papadaskalopoulou--2015a|Papadaskalopoulou et al., 2015a]] ; [[#Di%20Baldassarre--2018|Di Baldassarre et al., 2018]] ; [[#Garnier--2019|Garnier and Holman, 2019]] ). Wastewater reuse is considered a low-cost and effective measure where wastewater is available ( [[#Lavrnic--2017|Lavrnic et al., 2017]] ; [[#De%20Roo--2020|De Roo et al., 2020]] ), but public acceptance for domestic reuse is presently limited ( ''high confidence'' ) ( [[#Papadaskalopoulou--2015b|Papadaskalopoulou et al., 2015b]] ; [[#Morote--2019|Morote et al., 2019]] ). Increasing desalination capacity is used particularly in SEU but has high energy demands and produces brine waste ( [[#Garnier--2019|Garnier and Holman, 2019]] ; [[#Jones--2019|Jones et al., 2019]] ; [[#Morote--2019|Morote et al., 2019]] ).

Adaptation measures on the demand side include monitoring (e.g., water meters, early warning systems of drought) and regulating demand, for example, water restrictions, water pricing, water saving and efficiency measures, and land management and cover change ( [[#Papadaskalopoulou--2015b|Papadaskalopoulou et al., 2015b]] ; [[#Varela-Ortega--2016|Varela-Ortega et al., 2016]] ; [[#Manouseli--2018|Manouseli et al., 2018]] ; [[#Garnier--2019|Garnier and Holman, 2019]] ). Prolonged water restrictions and prioritising sectoral supply could result in economic losses (e.g., for irrigated agriculture) ( [[#13.5.2|Section 13.5.2]] ; [[#Wimmer--2014|Wimmer et al., 2014]] ; [[#Salmoral--2019|Salmoral et al., 2019]] ). Economic instruments, such as water pricing, can be effective when combined with incentives for water saving and efficiency ( [[#Kayaga--2014|Kayaga and Smout, 2014]] ; [[#Esteve--2018|Esteve et al., 2018]] ; [[#Crespo--2019|Crespo et al., 2019]] ). Water saving and efficiency measures, such as leakage repair, education and improved irrigation, could limit conflicts across sectors but necessitate technological advances and changes in practice together with a willingness to cooperate ( [[#Garnier--2019|Garnier and Holman, 2019]] ; [[#Papadimitriou--2019|Papadimitriou et al., 2019]] ; [[#Teotónio--2020|Teotónio et al., 2020]] ). Increased irrigation efficiency has reduced water scarcity, particularly in SEU ( [[#13.5|Section 13.5]] ; [[#De%20Roo--2020|De Roo et al., 2020]] ), and occur at farm level in WCE and NEU ( [[#Papadaskalopoulou--2015b|Papadaskalopoulou et al., 2015b]] ; [[#van%20Duinen--2015|van Duinen et al., 2015]] ; [[#Rey--2017|Rey et al., 2017]] ) but come with increasing path dependency on supply and trade-offs which may not be sustainable in the long term ( ''high confidence'' ) ( [[#Di%20Baldassarre--2018|Di Baldassarre et al., 2018]] ).

The assessment of the effectiveness and feasibility of adaptation options shows that a portfolio of supply-and-demand measures is needed to reduce water scarcity (Key Risk 3, [[#13.10.3|Section 13.10.3]] ), although locally demand-side measures could be sufficient ( [[#Kingsborough--2016|Kingsborough et al., 2016]] ). Under high warming levels, adaptation to drought and low flows by water saving and efficiency measures may not be sufficient to counteract reduced availability ( ''medium agreement, low evidence'' ) ( [[#Collet--2015|Collet et al., 2015]] ; [[#De%20Roo--2020|De Roo et al., 2020]] ). Successful adaptation in the water sector depends on integrating water considerations into sectoral policies ( [[#Collet--2015|Collet et al., 2015]] ; [[#Papadaskalopoulou--2016|Papadaskalopoulou et al., 2016]] ). Inclusive and participatory approaches where (local) stakeholders are actively involved in the initiation and execution of water management can enhance problem ownership, the quality and democratic legitimacy of processes and decisions, enhance support and accelerate decisions ( [[#Edelenbos--2017|Edelenbos et al., 2017]] ; [[#Begg--2018|Begg, 2018]] ).

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