Editing IPCC:AR6/WGII/Chapter-12 (section)

==== 12.5.3.1 Challenges and Opportunities ====

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In several regions of CSA, water scarcity is a serious challenge to local livelihoods and economic activities. Regions that are (seasonally) dry, partly with large populations and increasing water demand, exhibit particularly significant water stress. These include the Dry Corridor in CA, coastal areas of Peru (SWS) and northern Chile (SWS), the Bolivian-Peruvian Altiplano (NWS, SAM), the Dry Andes of Central Chile (SWS), Western Argentina and Chaco in northwestern Paraguay (SES) and Sertão in northeastern Brazil (NES) ( ''high confidence'' ) ( [[#Kummu--2016|Kummu et al., 2016]] ; [[#Mekonnen--2016|Mekonnen and Hoekstra, 2016]] ; [[#Schoolmeester--2018|Schoolmeester et al., 2018]] ). In NWS and SWS, downstream areas are increasingly affected by decreasing and unreliable river runoff due to rapid glacier shrinkage ( ''high confidence'' ) (Table SM12.6; [[#Carey--2014|Carey et al., 2014]] ; [[#Drenkhan--2015|Drenkhan et al., 2015]] ; [[#Buytaert--2017|Buytaert et al., 2017]] ). Many regions in CSA rely heavily on hydroelectric energy, and as a result of rising energy demand, hydropower capacity is constantly being extended ( [[#Schoolmeester--2018|Schoolmeester et al., 2018]] ). Worldwide, SA features the second-fastest growth rate, with about 5.2 GW additional annual capacity installed in 2019 ( [[#IHA--2020|IHA, 2020]] ). This development requires additional water storage options, which entail the construction of large dams and reservoirs with important social-ecological implications. River fragmentation and corresponding loss of habitat connectivity due to dam constructions have been described for, for example, the NSA, SAM, NES and SES ( ''high confidence'' ) ( [[#Grill--2015|Grill et al., 2015]] ; [[#Anderson--2018a|Anderson et al., 2018a]] ), with important implications for freshwater biota, such as fish migration ( ''medium confidence'' ) ( [[#Pelicice--2015|Pelicice et al., 2015]] ; [[#Herrera-R--2020|Herrera-R et al., 2020]] ). Furthermore, examples in, for instance, NWS ( [[#Carey--2012|Carey et al., 2012]] ; [[#Duarte-Abadía--2015|Duarte-Abadía et al., 2015]] ; [[#Hommes--2018|Hommes and Boelens, 2018]] ) and SWS ( [[#Muñoz--2019b|Muñoz et al., 2019b]] ) showcase unresolved water-related conflicts between local villagers, peasant communities, hydropower operators and governmental institutions in a context of distrust and lack of water governance ( ''high confidence'' ).

Increasing water scarcity is also shaped by poor water quality, which has barely been assessed in CSA. Declining water quality can be observed, for example, due to intense agricultural and industrial activities in SWS, SES and SSA ( ''medium confidence'' ) ( [[#Mekonnen--2015|Mekonnen et al., 2015]] ; [[#Gomez--2021|Gomez et al., 2021]] ), mining in Andean headwaters (NWS, SWS and Western SAM) and tropical lowlands (eastern SAM and NSA) ( ''medium confidence'' ) ( [[#Bebbington--2015|Bebbington et al., 2015]] risk and climate resilience; [[#Vuille--2018|Vuille et al., 2018]] ), urban domestic use ( [[#Desbureaux--2019|Desbureaux and Rodella, 2019]] ), decreasing meltwater contribution ( [[#Milner--2017|Milner et al., 2017]] ) and acid rock drainages from recently exposed glacial sediments ( [[#Santofimia--2017|Santofimia et al., 2017]] ; [[#Vuille--2018|Vuille et al., 2018]] ). The level of water pollution is often exacerbated by missing water treatment infrastructure and low governance levels ( ''medium confidence'' ) ( [[#Mekonnen--2015|Mekonnen et al., 2015]] ), with considerable negative implications for human health ( [[#Lizarralde%20Oliver--2016|Lizarralde Oliver and Ribeiro, 2016]] ).

Water scarcity risks are projected to affect a growing number of people in the near and mid-term future in view of growing water demand in most regions ( ''medium confidence: medium evidence, high agreement'' ) ( [[#Veldkamp--2017|Veldkamp et al., 2017]] ; [[#Schoolmeester--2018|Schoolmeester et al., 2018]] ; [[#Viviroli--2020|Viviroli et al., 2020]] ), expected precipitation reductions in western and northern SAM and SWS ( ''medium confidence: medium evidence, medium agreement'' ) ( [[#Neukom--2015|Neukom et al., 2015]] ; [[#Schoolmeester--2018|Schoolmeester et al., 2018]] ), substantial vanishing of glacier extent in NWS, SAM and SWS (Table SM12.6; [[#Rabatel--2018|Rabatel et al., 2018]] ; [[#Vuille--2018|Vuille et al., 2018]] ; [[#Cuesta--2019|Cuesta et al., 2019]] ; [[#Drenkhan--2019|Drenkhan et al., 2019]] ) and increasing evaporation rates in CA ( ''medium confidence'' ) ( [[#CEPAL--2017|CEPAL, 2017]] ). Furthermore, flood risk is a serious concern ( [[#Arnell--2016|Arnell et al., 2016]] ) and expected to increase, especially in NWS, SAM, SES and SWS in the mid- and long-term future ( ''high confidence'' ) ( [[#Arnell--2016|Arnell and Gosling, 2016]] ; [[#Alfieri--2017|Alfieri et al., 2017]] ).

Risks of water scarcity and flood threaten people unevenly across the region. In CSA, about 26% (130 million people) of the population have no access to safe drinking water, and strong disparities prevail regarding its spatial distribution; for example, in Chile, 99% of the population have access, compared to 50% in Peru, 73% in Colombia, 52% in Nicaragua or 56% in Guatemala ( ''high confidence'' ) ( [[#UNICEF%20and%20WHO--2019|UNICEF and WHO, 2019]] ). Inequalities can be further exacerbated by unregulated or privately owned water rights and allocation systems (e.g., in Chile) ( [[#Muñoz--2020a|Muñoz et al., 2020a]] ). The most vulnerable people belong to low-income groups in rural areas and informal settlements of large urban areas ( ''high confidence'' ) ( [[#WWAP--2020|WWAP, 2020]] ).

Considerable uncertainties remain concerning future hydrological risks that strongly depend on the respective pathways of human intervention, management, adaptation and socioeconomic development. The combination of (seasonally) reduced water supply, growing water demand, declining water quality, ecosystem deterioration and habitat loss and low water governance could lead to increasing competition and conflict associated with high economic losses ( ''high confidence'' ) ( [[#Vergara--2007|Vergara et al., 2007]] ; [[#Vuille--2018|Vuille et al., 2018]] ; [[#Desbureaux--2019|Desbureaux and Rodella, 2019]] ). This situation threatens human water security in the long term and poses an increasing risk to adaptation success in CSA ( ''high confidence'' ) ( [[#Drenkhan--2015|Drenkhan et al., 2015]] ; [[#Huggel--2015b|Huggel et al., 2015b]] ; [[#Urquiza--2020a|Urquiza and Billi, 2020a]] ).

Important progress has been made on climate change and water management policies in combination with more inclusive stakeholder processes. For instance, the implementation of NDCs in most countries of the region provides an important baseline for improving water efficiency, quality and governance at a multi-sectoral level and, thus, long-term adaptation planning ( [[#UNEP--2015|UNEP, 2015]] ).

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