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

=== 12.5.3 Water ===

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CSA is one of the regions most affected by current and future hydrological risks to water security with an increasing number of vulnerable people depending on water from mountains ( ''high confidence'' ) (Sections 4.3, 4.4, 4.5; [[#Immerzeel--2020|Immerzeel et al., 2020]] ; [[#Viviroli--2020|Viviroli et al., 2020]] ; [[#WWAP--2020|WWAP, 2020]] ). Adaptation to changing water availability is therefore a priority, but most efforts are documented only in the grey literature (e.g., governmental documents, project reports) with highly variable standards of quality and evidence. Most of the documented adaptation initiatives are in an early planning or implementation stage and evidence on successful outcomes is quite limited ( [[#Berrang-Ford--2021|Berrang-Ford et al., 2021]] ). However, the growing number of adaptation initiatives across the CSA region has contributed to improved understanding of complex interlinkages of climate change, human vulnerabilities, local policies and feasible adaptation approaches ( [[#McDowell--2019|McDowell et al., 2019]] ).

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==== 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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==== 12.5.3.2 Main Concepts and Approaches ====

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Adaptation in the water sector includes a broad set of responses to improve and transform, for example, water infrastructure, ecosystem functions, institutions, capacity building and knowledge production, habits and culture and local-national policies ( [[IPCC:Wg2:Chapter:Chapter-4#4.6|Section 4.6]] ).

Most adaptive water management approaches in CSA centre around extending the water supply side, including large infrastructure projects. However, ‘hard path’ interventions are now strongly contested because negative effects exacerbate local water conflicts ( [[#Carey--2012|Carey et al., 2012]] ; [[#Boelens--2019|Boelens et al., 2019]] ; [[#Drenkhan--2019|Drenkhan et al., 2019]] ), potentially leading to increasing water demand, vulnerabilities and water shortage risks ( [[#Di%20Baldassarre--2018|Di Baldassarre et al., 2018]] ), thereby limiting adaptive capacity ( ''high confidence'' ) ( [[#Ochoa-Tocachi--2019|Ochoa-Tocachi et al., 2019]] ). More integrated approaches focus on multiple uses of water storage with shared stakeholder vision, responsibilities, rights and costs, as well as risks and benefits, and often integrating water and risk management ( [[#Branche--2017|Branche, 2017]] ; [[#Haeberli--2017|Haeberli et al., 2017]] ; [[#Drenkhan--2019|Drenkhan et al., 2019]] ). In this chapter, a feasibility assessment was carried out for six major dimensions of multi-use water storage for the entire CSA (Table 12.11). While geophysical and economic aspects allow for the implementation of water storage projects under a multi-use approach, the institutional, social and environmental dimensions pose a major barrier ( [[#12.5.3|Section 12.5.3]] ). Further demand-oriented approaches focus on incentives for the reduction of water use through changes in people’s habits, efficiency increase and smart water management ( [[#Gleick--2002|Gleick, 2002]] ). These are promoted in some regions, such as in CA and NWS (e.g., Colombia, Ecuador and Peru), to foster a sustainable water culture ( [[#Bremer--2016|Bremer et al., 2016]] ; [[#Paerregaard--2016|Paerregaard et al., 2016]] ).

Major emphasis has been placed on NbS, that is, catchment interventions that are inspired and supported by nature and leverage natural processes and ecosystem services to contribute to the improved management of water. NbS potentially enhance water infiltration, groundwater recharge and surface storage, contribute to disaster risk reduction and can replace or complement grey (i.e., conventionally built) infrastructure that is often socioenvironmentally contested ( [[#WWAP--2018|WWAP, 2018]] ). Some examples include the reactivation of ancestral infiltration enhancement systems in the Peruvian Andes (NWS) ( [[#Ochoa-Tocachi--2019|Ochoa-Tocachi et al., 2019]] ), the use of erosion control structures in the Bolivian Altiplano (SAM) ( [[#Hartman--2016|Hartman et al., 2016]] ) and the potential improvement of drinking water quality and flood risk reduction in urban areas of CSA ( [[#Tellman--2018|Tellman et al., 2018]] ) ( [[#12.5.5.3.2|Section 12.5.5.3.2]] ). Additionally, NbS in combination with ecosystem and community-based adaptation potentially generate important co-benefits, including increasing water security and the attenuation of social conflicts in Chile (SWS) ( [[#Reid--2018|Reid et al., 2018]] ), water conservation in coastal Peru (NWS) and flood protection in Guyana (NSA) ( ''medium confidence: medium evidence, medium agreement'' ) ( [[#Spencer--2017|Spencer et al., 2017]] ). However, the evaluation of implementation success of NbS is often hampered by limited evidence on actual benefits ( [[#WWAP--2018|WWAP, 2018]] ).

In recent years, the inclusion of IKLK in current adaptation baselines has attracted increasing attention, particularly in regions with a high share of Indigenous Peoples (NWS, SAN, SWS, NSA) ( ''high confidence'' ) ( [[#Reyes-García--2016|Reyes-García et al., 2016]] ; [[#Schoolmeester--2018|Schoolmeester et al., 2018]] ; [[#McDowell--2019|McDowell et al., 2019]] ). One example is the adapted use of agrobiodiversity when dealing with more frequent and intense tidal floods in the Amazon delta (NSA) ( [[#Vogt--2016|Vogt et al., 2016]] ). In another context, IKLK has been considered for the evaluation of water scarcity and GLOF risks in Peru (NWS) ( [[#Motschmann--2020b|Motschmann et al., 2020b]] ). Additionally, local citizen science-based initiatives ( [[#Buytaert--2014|Buytaert et al., 2014]] ; [[#Tellman--2016|Tellman et al., 2016]] ; [[#Njue--2019|Njue et al., 2019]] ) can support the production of multiple forms of knowledge with flexible and extensive data collection. Important questions centre around how to integrate IKLK and other types of knowledge from the early planning stages on, to achieve enhanced or transformational adaptation building on co-produced knowledge ( [[#Kates--2012|Kates et al., 2012]] ; [[#Klenk--2017|Klenk et al., 2017]] ). NbS combined with community engagement and integration of diverse knowledge can foster transformational adaptation of social-ecological systems ( [[#Palomo--2021|Palomo et al., 2021]] ).

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==== 12.5.3.3 Policies, Governance and Financing ====

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National policies on climate change, water protection, regulation and management laws are important focal areas of adaptation in the water sector ( [[IPCC:Wg2:Chapter:Chapter-4#4.7|Section 4.7]] ). Notable in the jurisdiction field is the Glacier Protection Law in place in Argentina (2010–2019) and under construction in Chile (since 2005). This first glacier law in the world represents a milestone for high-mountain conservation but is also criticised for hindering effective disaster risk adaptation measures and excluding local socioeconomic needs ( [[#Anacona--2018|Anacona et al., 2018]] ). Furthermore, the first Framework Law on Climate Change was implemented in Peru (2018) and is under way in Colombia, Chile and Venezuela (Figure 12.13; Table SM12.6). Overarching regional institutions (e.g., OAS [2016] ''')''' and most countries in CSA promote a move towards more integrative and sustainable management of water resources through new legislation and financing mechanisms. For instance, new water laws that include principles of integrated water resource management (IWRM) have entered into force, for example, in Nicaragua (2007), Peru (2009), Ecuador (2014) and Costa Rica (2014), or are under way, such as in Colombia (since 2009). However, current realities in all regions show major challenges in implementing IWRM mechanisms and policies, related but not limited to political and institutional instabilities, governance structures, fragmented service provision, lack of economies of scale and scope, corruption and social conflicts ( ''high confidence'' ) ( [[#WWAP--2020|WWAP, 2020]] ).

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[[File:708f40e14087168944d643627a1993b1 IPCC_AR6_WGII_Figure_12_013.png]]

'''Figure 12.13 |''' '''Overview map of observed glacier changes, associated impacts, adaptation and policy efforts across the Andes.'''

'''(a)''' Selected impacts from glacier shrinkage.

'''(b)''' Selected adaptation efforts (see upper-right map for the location of each adaptation measure).

'''(c)''' Policies and glacier inventory: NDC = submission year(s) of Nationally Determined Contributions (u = update), CCL = climate change law, GLL = glacier law (i = initialised framework), INV = last national glacier inventory. The explicit mention of glaciers, snow and mountain ecosystems within each law/inventory is highlighted with the corresponding symbols (grey = has not come into force).

'''(d)''' Glacier area (km²) according to last national inventory.

'''(e)''' Glacier area change (%/year) according to baseline of last national inventory.

'''(f)''' Geodetic glacier mass balance in metres water equivalent per year (m w.e./year) and error estimate (±m w.e./year) retrieved from [[#Dussaillant--2019|Dussaillant et al. (2019)]] . nd = no data available. Further details can be found in the appendix in Table SM12.6.

Many water-related conflicts in CSA are rooted in inequitable water governance that excludes water users from decisions on water allocation ( ''high confidence'' ) ( [[#Drenkhan--2015|Drenkhan et al., 2015]] ; [[#Vuille--2018|Vuille et al., 2018]] ). In turn, inclusive water regimes leverage long-term adaptation planning. These have been addressed in some national strategies, such as in Brazil ( [[#Ministry%20of%20Environment%20of%20Brazil--2016a|Ministry of Environment of Brazil, 2016a]] ). At the local level, a decentralised and participatory bottom-up water governance model was induced by civil society and research institutions to foster rainwater harvesting technologies reducing drought risk in semiarid Brazil (NES) ( [[#Lindoso--2018|Lindoso et al., 2018]] ).

Water fund programmes can generate important co-benefits for sustainable development, contributing to improved governance and conservation of watershed systems in CSA. Nevertheless, only a few experiences have been evaluated as successful due to insufficient implementation, low decision-making ability of some stakeholder groups and poor evidence-based approaches ( ''medium confidence'' ) ( [[#Bremer--2016|Bremer et al., 2016]] ; [[#Leisher--2019|Leisher et al., 2019]] ). Furthermore, financing mechanisms that produce incentives for sustainable water management have been promoted, tested or implemented. PES for water provision represents such an example and such mechanisms have been implemented across CSA since the 1990s ( [[#Grima--2016|Grima et al., 2016]] ).

Only about 50–70% of required financial resources are currently allocated per year to meet the national targets in the water, sanitation and hygiene (WASH) sector for the Sustainable Development Goal (SDG) 6 agenda in several regions of CSA. This share drops down to less than 50% in NSA (Venezuela) and SES (Argentina, Uruguay, Paraguay), except for Panama in CA, which allocates more than 75% of the required financial resources. For the implementation of NbS, evidence suggests that the overall expenditure remains well below 1% of total investment in water resource management infrastructure ( [[#WWAP--2018|WWAP, 2018]] ). These funding deficits set important limitations on future water provision, adaptation to changing water resources and the achievement of the SDGs by 2030 ( ''high confidence'' ) ( [[#WHO--2017|WHO, 2017]] ).

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==== 12.5.3.4 Successful Adaptation and Limitations ====

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Although a growing body of adaptation initiatives exists for CSA, evidence on their effectiveness is scarce. In many parts of CSA the level of success of adaptation measures depends largely on the governance of projects and stakeholder-based processes and is closely related to their effectiveness, efficiency, social equity and sociopolitical legitimacy ( ''high confidence'' ) ( [[#Adger--2005|Adger et al., 2005]] ; [[#Rasmussen--2016b|Rasmussen, 2016b]] ; [[#Moulton--2021|Moulton et al., 2021]] ). Several PES experiences across CSA have been described as successful measures for watershed conservation and adaptation ( ''high confidence'' ). An example of success is the Quito water fund in Ecuador, which aims to improve the city’s water quality by integrating public and private stakeholder interests with ecosystem conservation and local community development since the 2000s ( [[#Bremer--2016|Bremer et al., 2016]] ; [[#Grima--2016|Grima et al., 2016]] ) (Case Study 12.6.1). At the same time, in Moyobamba in Peru, the development of a watershed protection programme was leveraged by a multi-stakeholder platform process that enabled deep social learning ( [[#Lindsay--2018|Lindsay, 2018]] ). In turn, initiatives that do not consider the entire set of social-ecological dimensions and dynamics of adaptation or unintentionally increase vulnerabilities of human or natural systems are at risk of leading to reduced outcomes ( [[#McDowell--2021|McDowell et al., 2021]] ) or maladaptation ( [[#Reid--2018|Reid et al., 2018]] ; [[#McDowell--2019|McDowell et al., 2019]] ; [[#Eriksen--2021|Eriksen et al., 2021]] ). However, systematic assessments of maladaptation in the water sector have barely been provided for CSA.

In CSA, only limited information on the limits of adaptation in relation to water is available, for instance on the possible path dependency of institutions and associated resistance to change ( [[#Barnett--2015|Barnett et al., 2015]] ). Examples of soft adaptation limits (i.e., options to avoid intolerable risks currently not available) include lack of trust and stakeholder flexibility, associated with unequal power relations that lead to reduced social learning and poor outcomes for improved water management, as reported in, for example, NWS ( [[#Lindsay--2018|Lindsay, 2018]] ). An example of hard adaptation limits (i.e., intolerable risks cannot be avoided) in the region is the loss of livelihoods and cultural values associated with glacier shrinkage in NWS ( [[#Jurt--2015|Jurt et al., 2015]] ).

Most barriers to advance adaptation in CSA correspond to soft limits associated with missing links of science–society–policy processes, institutional fragilities, pronounced hierarchies, unequal power relations and top-down water governance regimes ( ''high confidence'' ). One example is the abandonment of long-term hydrological monitoring sites within tropical Andean ecosystems (paramo) in Venezuela ( [[#Rodríguez-Morales--2019|Rodríguez-Morales et al., 2019]] ) due to the lack of governmental support during the political crisis. In that regard, the collection and availability of consistent hydroclimatic and socioeconomic data at adequate scales represent an important challenge in CSA. Major adaptation barriers are furthermore reported from central Chile in the context of a mega-drought since 2010, related to socioeconomic factors and a deficient bottom-up approach to informing and developing public policy ( [[#Aldunce--2017|Aldunce et al., 2017]] ). These gaps could be bridged by strengthening transdisciplinary approaches at the science–policy interface ( [[#Lillo-Ortega--2019|Lillo-Ortega et al., 2019]] ) with blended bottom-up and top-down adaptation to include scientific knowledge with impact and scenario assessments in local adaptation agendas ( [[#Huggel--2015b|Huggel et al., 2015b]] ). For instance, a new allocation rule for the Laja reservoir in southern Chile (SWS), based on consistent water balance modelling results, could inform policy and water management and potentially improve local water management and reduce water conflicts over the long term ( [[#Muñoz--2019b|Muñoz et al., 2019b]] ).

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