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

== 4.5 Projected Sectoral Water-Related Risks ==

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Observed sectoral water-related impacts have been documented across world regions. Climate change is projected to further exacerbate many of these risks, especially at warming levels above 1.5°C (Figure 4.20). For some sectors and regions, climate change may also hold the potential for beneficial outcomes, though feedback and cascading effects as well as risks of climate extremes are not always well understood and often underestimated in impact projections. Risks manifest as a consequence of the interplay of human and natural vulnerability, sector-specific exposure as well as the climate hazard as a driver of climate change. Challenges to water security are driven by factors across these components of risk, where climate change is but one facet of driving water insecurity in the face of global change. While the focus of this chapter is on climate change and its effects on water security, for many sectors and regions the dynamics of socioeconomic conditions is a core driver. They play an essential role in understanding and alleviating water security risks. The following sections outline sectoral risks for both, risks driven by water-related impacts, such as drought, flood or changes in water availability, as well as risks with effects on water uses, mainly focusing on changing water demand as a consequence of climate change. It therefore does not cover all climate change-driven risks to the respective sectors, but is limited to those that stand in relation to water. The focus within this chapter is on global to regional processes (additional regional to local information in Table SM4.4; Figure 4.20 as well as across regional chapters of this report).

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[[File:5b16ae2d8a031d0748973b34cbf5f45c IPCC_AR6_WGII_Figure_4_020.png]]

'''Figure 4.20 |''' '''Regional synthesis of changes in water and consequent impacts assessed in this chapter.'''

'''(a)''' Regional changes and impacts of selected variables. Confidence levels higher than medium are shown.

'''(b)''' Assessment result of all variables. For each region, physical changes, impacts on ecosystems and impacts on human systems are shown. For physical changes, upward/downward triangles refer to an increase/decrease, respectively, in the amount or frequency of the measured variable, and the level of confidence refers to confidence that the change has occurred. For impacts on ecosystems and human systems, plus or minus marks depict whether an observed impact of hydrological change is positive (beneficial) or negative (adverse), respectively, to the given system, and the level of confidence refers to confidence in attributing an impact on that system to a climate-induced hydrological change. The hydrological impact may be different to the overall change in the system; for example, over much of the world, crop yields have increased overall, largely for non-climatic reasons, but in some areas, hydrological impacts of climate change are countering this. Circles indicate that within that region, both increase and decrease of physical changes are found, but are not necessarily equal; the same holds for cells showing ‘both’ assessed impacts. Cells assigned ‘n.a.’ indicates variables not assessed due to limited evidences. Decrease (increase) in water quality refers to adverse (positive) change in quality. Agriculture refers to impacts on crop production. Note: Energy refers to impacts on hydro and thermoelectric power generation. Ecosystems refers to impacts on freshwater ecosystem.

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=== 4.5.1 Projected Risks to Agriculture ===

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AR5 concluded that overall irrigation water demand would increase by 2080, while the vulnerability of rain-fed agriculture will further increase ( [[#Jiménez%20Cisneros--2014|Jiménez Cisneros et al., 2014]] ). SR1.5 concluded that both the food and the water sectors would be negatively impacted by global warming with higher risks at 2°C than at 1.5°C, and these risks could coincide spatially and temporally, thus increasing hazards, exposures and vulnerabilities across populations and regions ( ''medium confidence'' ). SR1.5 further reinforced AR5 conclusions in terms of projected crop yield reductions, especially for wheat and rice ( ''high confidence'' ), loss of livestock and increased risks for small-scale fisheries and aquaculture ( ''medium confidence'' ) ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ), conclusions which are further corroborated by SRCCL ( [[#Mbow--2019|Mbow et al., 2019]] ).

Climate change impacts agriculture through various pathways (5.4 – Crop-based Systems), with projected yield losses of up to 32% by 2100 (RCP8.5) due to the combined effects of temperature and precipitation. Limiting warming could significantly reduce potential impacts (up 12% yield reduction by 2100 under RCP4.5) ( [[#Ren--2018a|Ren et al., 2018a]] ). Though overall changes differ across models, regions and seasons, differences in impacts between 1.5°C and 2°C can also be identified ( [[#Ren--2018a|Ren et al., 2018a]] ; [[#Ruane--2018|Ruane et al., 2018]] ; [[#Schleussner--2018|Schleussner et al., 2018]] ). Globally, 11% (± 5%) of croplands are estimated to be vulnerable to projected climate-driven water scarcity by 2050 ( [[#Fitton--2019|Fitton et al., 2019]] ).

Overall drought-driven yield loss is estimated to increase by 9–12% (wheat), 5.6–6.3% (maize), 18.1–19.4% (rice) and 15.1–16.1% (soybean) by 2071–2100, relative to 1961–2016 (RCP8.5) ( [[#Leng--2019|Leng and Hall, 2019]] ). In addition, temperature-driven increases in water vapour deficit could have additional negative effects, further exacerbating drought-induced plant mortality and thus impacting yields ( [[#Grossiord--2020|Grossiord et al., 2020]] ) (see also Cross-Chapter Box 1 in [[IPCC:Wg2:Chapter:Chapter-5|Chapter 5]] of WGI report). Currently, global agricultural models do not fully differentiate crop responses to elevated CO 2 under temperature and hydrological extremes ( [[#Deryng--2016|Deryng et al., 2016]] ) and largely underestimate the effects of climate extremes ( [[#Schewe--2019|Schewe et al., 2019]] ).

Flood-related risks to agricultural production are projected to increase over Europe, with a mean increase of expected annual output losses of approximately €11 million (at 1.5°C GWL); €12 million ( at 2°C GWL) and €15 million (at 3°C GWL) relative to the 2010 baseline ( [[#Koks--2019|Koks et al., 2019]] ). In parts of Asia, where flooding impacts on agriculture are already significant, projections indicate an increase in damage to area under paddy by up to 50% in Nepal, 16% in the Philippines, 55% in Indonesia, 23% in Cambodia and Vietnam and 13% in Thailand (2075–2099 compared with 1979–2003; RCP8.5) ( [[#Shrestha--2019a|Shrestha et al., 2019a]] ).

Global crop water consumption of green water resources (soil moisture) is projected to increase by about 8.5% by 2099 relative to 1971–2000 as a result of climate drivers (RCP6.0), with additional smaller contributions by land use change ( [[#Huang--2019|Huang et al., 2019]] ) (Sections 4.4.1.3, 4.4.8). In India, a substantial increase in green and blue water consumption is projected for wheat and maize, with a slight reduction of blue water consumption for paddy fields ( [[#Mali--2021|Mali et al., 2021]] ). Temperate drylands, especially higher latitude regions, may become more suitable for rain-fed agriculture ( [[#Bradford--2017|Bradford et al., 2017]] ). Locally and regionally, however, some of those areas with currently larger areas under rain-fed production, for example, in Europe, may become less suitable for rain-fed agriculture (Table 1 to 4.5.1) ( [[#Bradford--2017|Bradford et al., 2017]] ; [[#Shahsavari--2019|Shahsavari et al., 2019]] ).

While global crop models and estimates of yield impacts often focus on major staple crops relevant for global food security, crops of high economic value are projected to become increasingly water dependent. For example, climate-driven yield increases for tea are projected for various tea-producing regions if no water limitations and full irrigation is assumed, but decreases in yields are projected under continued present-day irrigation assumptions ( [[#Beringer--2020|Beringer et al., 2020]] ). Water-related impacts on global cotton production are highly dependent on the CO 2 -fertilisation effect, with increases projected for higher CO 2 concentration if no water limitations are implemented. However, substantial decreases in cotton production are projected if lower or no fertilisation effects are accounted for due to increasing water limitations ( [[#Jans--2018|Jans et al., 2018]] ). Reductions in economically valuable crops will probably increase the vulnerability of population groups, especially small-holder farmers with limited response options ( [[#Morel--2019|Morel et al., 2019]] ).

To stabilise yields against variations in moisture availability, irrigation is the often the most common adaptation response ( [[#4.6.2|Section 4.6.2]] , Box 4.3). Projections indicate a potentially substantial increase in irrigation water requirements ( [[#Boretti--2019|Boretti and Rosa, 2019]] ). Increasing agricultural water demand is driven by various factors, including population growth, increased irrigated agriculture, cropland expansion and higher demand for bio-energy crops for mitigation ( [[#Chaturvedi--2015|Chaturvedi et al., 2015]] ; [[#Grafton--2015|Grafton et al., 2015]] ; [[#Turner--2019|Turner et al., 2019]] ; 4.7.6). Depending on underlying assumptions and the constraints on water resources implemented in the global agricultural models, irrigation water requirements are projected to increase two- to three-fold by the end of the century ( [[#Hejazi--2014|Hejazi et al., 2014]] ; [[#Bonsch--2015|Bonsch et al., 2015]] ; [[#Chaturvedi--2015|Chaturvedi et al., 2015]] ; [[#Huang--2019|Huang et al., 2019]] ). While the combined effects of population and land use change as well as irrigation expansion account for the significant part of the projected increases in irrigation water demand by the end of the century, around 14% of the increase is directly attributed to climate change (RCP6.0) ( [[#Huang--2019|Huang et al., 2019]] ).

With various degrees of water stress being experienced under current conditions and further changes in regional water availability projected, as well as continuing groundwater depletion as a consequence of over-abstraction for irrigation purposes (Sections 4.2.6 and 4.4.6), limitations to major irrigation expansion will occur in some regions, including South and Central Asia, the Middle East and parts of North and Central America ( [[#Grafton--2015|Grafton et al., 2015]] ; [[#Turner--2019|Turner et al., 2019]] ). Constraining projections of available irrigation water through consideration of environmental flow requirements further reduces the potential for irrigation capacity and expansion ( [[#Bonsch--2015|Bonsch et al., 2015]] ). Changes in land use and production patterns, for example, expansion of rain-fed production and increasing inter-regional trade, would be required to meet growing food demand while preserving environmental flow requirements, though this may increase local food security-related vulnerabilities (Cross-Chapter Box INTERREG in Chapter 16) ( [[#Pastor--2014|Pastor et al., 2014]] ). Where climate impacts on yields are not a consequence of water limitations (mainly for C4 crops), irrigation cannot offset negative yield impacts ( [[#Levis--2018|Levis et al., 2018]] ).

Over 50% of the global lowlands equipped for irrigation will depend heavily on runoff contributions from the mountain cryosphere by 2041–2050 (SSP2–RCP6.0) and are projected to make unsustainable use of blue water resources ( [[#Viviroli--2020|Viviroli et al., 2020]] ). Projected changes in snowmelt patterns indicate that for all regions dependent on snowmelt for irrigation during warm seasons, alternative water sources will have to be found for up to 20% (at 2°C GWL) and up to 40% (at 4°C GWL) of seasonal irrigation water use, relative to current water use patterns (1986–2015) ( [[#Qin--2020|Qin et al., 2020]] ). Regional studies further corroborate these global findings ( [[#Biemans--2019|Biemans et al., 2019]] ; [[#Malek--2020|Malek et al., 2020]] ). Basins where such alternate sources are not available will face agricultural water scarcity.

Elevated CO 2 concentrations play an important role in determining future yields in general and have the potential to beneficially affect plant water use efficiency ( [[#Deryng--2016|Deryng et al., 2016]] ; [[#Ren--2018a|Ren et al., 2018a]] ; [[#Nechifor--2019|Nechifor and Winning, 2019]] ). The elevated CO 2 effects are projected to be most prominent for rain-fed C3 crops ( [[#Levis--2018|Levis et al., 2018]] ). Combined results from field experiments and global crop models show that CO 2 fertilisation could reduce consumptive water use by 4–17% ( [[#Deryng--2016|Deryng et al., 2016]] ). To account for uncertainties, global agricultural models provide output with and without account for CO 2 fertilisation effects, though recent progress on reducing model uncertainty indicates that non-CO 2 model runs may no longer be needed for adequate projections of yield impacts ( [[#Toreti--2019|Toreti et al., 2019]] ).

Due to the complex interactions among determinants for livestock production, the future signal of water-related risks to this sector is unclear. Globally, 10% (± 5%) of pasture areas are projected to be vulnerable to climate-induced water scarcity by 2050 ( [[#Fitton--2019|Fitton et al., 2019]] ). Water use efficiency gains through elevated CO 2 concentrations have the potential to increase forage quantities, though effects of nutritional values are ambiguous ( [[#Augustine--2018|Augustine et al., 2018]] ; [[#Derner--2018|Derner et al., 2018]] ; [[#Rolla--2019|Rolla et al., 2019]] ). In addition, spatial shifts in temperature/humidity regimes may shift suitable regions for livestock production, opening up new suitable areas for some regions or encouraging shifts in specific breeds better adapted to future climatic regimes ( [[#Rolla--2019|Rolla et al., 2019]] ) (5.5 – Livestock Systems and 5.10 Mixed Systems).

Projections of climate impacts on freshwater aquaculture are limited (5.9.3.1 – Projected Impacts; Inland freshwater and brackish aquaculture). In particular, in tropical regions, reductions in water availability, deteriorating water quality, and increasing water temperatures pose risks to terrestrial aquaculture, including temperature-related diseases and endocrine disruption ( [[#Kibria--2017|Kibria et al., 2017]] , [[#4.4.7|Section 4.4.7]] ). On the other hand, freshwater aquaculture in temperate and arctic polar regions may benefit from temperature increases with an extension of the fish-growing season ( [[#Kibria--2017|Kibria et al., 2017]] ).

Global crop models, which provide the basis for most projections of agricultural risk, continue to have limitations in resolving water availability. For example they do not fully resolve the effects of elevated CO 2 for changing water use efficiency ( [[#Durand--2018|Durand et al., 2018]] ), potentially overestimating drought impacts on maize yield ( [[#Fodor--2017|Fodor et al., 2017]] ) and may underestimate limitations to further expansion of irrigation ( [[#Elliott--2014|Elliott et al., 2014]] ; [[#Frieler--2017b|Frieler et al., 2017b]] ; [[#Winter--2017|Winter et al., 2017]] ; [[#Jägermeyr--2018|Jägermeyr and Frieler, 2018]] ; [[#Kimball--2019|Kimball et al., 2019]] ; [[#Yokohata--2020a|Yokohata et al., 2020a]] ).

In summary, agricultural water use is projected to increase globally due to cropland expansion and intensification and climate change-induced changes in water requirements ( ''high confidence'' ). Parts of temperate drylands may experience increases in suitability for rain-fed production based on mean climate conditions; however, risks to rain-fed agriculture increase globally because of increasing variability in precipitation regimes and changes in water availability ( ''high confidence'' ). Water-related impacts on economically valuable crops will increase regional economic risks ( ''medium evidence, high agreement'' ). Regions reliant on snowmelt for irrigation purposes will be affected by substantial reductions in water availability ( ''high confidence'' ).

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=== 4.5.2 Projected Risks to Energy and Industrial Water Use ===

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AR5 concluded with ''high confidence'' that climate-induced changes, including changes in water flows, will affect energy production, and the actual impact will depend on the technological processes and location of energy production facilities ( [[#Arent--2014|Arent et al., 2014]] ). SR1.5 concluded with ''high confidence'' that climate change is projected to affect the hydropower production of northern European countries positively. However, Mediterranean countries like Greece, Spain and Portugal are projected to experience approximately a 10% reduction in hydropower potential under a 2°C warming level, which could be reduced by half if global warming could be limited to 1.5°C ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). In addition, SROCC concluded with ''high confidence'' that an altered amount and seasonality of water supply from snow and glacier melt is projected to affect hydropower production negatively ( [[#IPCC--2019a|IPCC, 2019a]] ).

Since AR5, a large number of studies have modelled future changes in hydropower production due to climate-induced changes in volume and seasonality of streamflow and changes in sediment load due to accelerated melting of cryosphere at both global ( [[#van%20Vliet--2016b|van Vliet et al., 2016b]] ; [[#Turner--2017|Turner et al., 2017]] ) and regional scales ( [[#Tarroja--2016|Tarroja et al., 2016]] ; [[#Ali--2018|Ali et al., 2018]] ; [[#de%20Jong--2018|de Jong et al., 2018]] ; [[#Tobin--2018|Tobin et al., 2018]] ; [[#Arango-Aramburo--2019|Arango-Aramburo et al., 2019]] ; [[#Carvajal--2019|Carvajal et al., 2019]] ; [[#Arias--2020|Arias et al., 2020]] ; [[#Meng--2021|Meng et al., 2021]] ).

For hydropower production at a global scale, Turner et al. (2017) projected an uncertainty in the direction of change in global hydropower production to the tune of +5% to −5% by the 2080s, under a high-emissions scenario. On the other hand, [[#van%20Vliet--2016b|van Vliet et al. (2016b)]] projected an increase in global hydropower production between +2.4% to +6.3% under RCP4.5 and RCP8.5, respectively, by the 2080s, as compared to a baseline period of 1971–2000, but with significant regional variations ( ''high confidence'' ). For example, regions like central Africa, India, central Asia and northern high-latitude areas are projected to see more than 20% increases in gross hydropower potential ( ''high confidence'' ). On the other hand, southern Europe, northern Africa, southern USA and parts of South America, southern Africa and southern Australia are projected to experience more than 20% decreases in gross hydropower potential. The Mediterranean region is projected to see almost a 40% reduction in hydropower production ( ''high confidence'' ) ( [[#Turner--2017|Turner et al., 2017]] ). On the other hand, northern Europe and India are projected to add to their hydropower production capacity due to climate change by mid-century ( ''high confidence'' ) ( [[#van%20Vliet--2016b|van Vliet et al., 2016b]] ; [[#Turner--2017|Turner et al., 2017]] ; [[#Emodi--2019|Emodi et al., 2019]] ).

In hydropower plants located in the Zambezi basin, electricity output is projected to decline by 10–20% by 2070 compared to baseline (1948–2008) under a drying climate; only marginal increases are projected under a wetting climate ( [[#Spalding-Fecher--2017|Spalding-Fecher et al., 2017]] ). In the Mekong Basin, the total hydropower generation is projected to decline by 3.0% and 29.3% under 1.5°C and 2°C, respectively ( [[#Meng--2021|Meng et al., 2021]] ). In this context, 1.5°C will come up in 2036 under RCP2.6 and in 2033, under RCP6.0; and 2°C will come up in 2056 under RCP6.0 ( [[#Frieler--2017a|Frieler et al., 2017a]] ). In India, hydropower production is projected to increase by up to 25% by the end of the 21st century due to increased temperature and precipitation under the RCP8.5 scenario. However, hydropower production is projected to decline in plants located in snow-dominated rivers due to earlier snowmelt ( [[#Ali--2018|Ali et al., 2018]] ). In Colombia, hydropower production is projected to decrease by ~10% under the RCP4.5 dry scenario by 2050 ( [[#Arango-Aramburo--2019|Arango-Aramburo et al., 2019]] ). In a sub-basin of the Amazon River (one of the hydropower hotspots in Brazil), dry-season hydropower potential is projected to decline by −7.4 to −5.4% from historical baseline conditions under RCP4.5 ( [[#Arias--2020|Arias et al., 2020]] ). In the São Francisco basin of Brazil, hydropower production is projected to reduce by −15% to −20% by 2100 under the IPCC A1B scenario ( [[#de%20Jong--2018|de Jong et al., 2018]] ), which will affect the Brazilian energy mix in the future. In Ecuador, under various policy pathways and dry and wet scenarios under RCP4.5, hydropower production is projected to increase by +7% to +21% or decline by −25% to −44% by 2050 ( [[#Carvajal--2019|Carvajal et al., 2019]] ). In Europe, different impacts are projected across different sub-regions (WGII, Chapter 13, Table 13.7- Projected climate change risks for energy supply in Europe by 2100). In northern Europe, up to 20% of hydropower potential increases are projected under 3°C warming; increases of up to 15% and 10% are projected under 2°C and 1.5°C warming levels. In Mediterranean parts of Europe, hydropower potential reductions of up to −40% are projected under 3°C warming; while reductions below −10% and −5% are projected under 2°C and 1.5°C warming levels, respectively ( [[#van%20Vliet--2016b|van Vliet et al., 2016b]] ; [[#Tobin--2018|Tobin et al., 2018]] ). Hydropower plants in Switzerland are projected to lose ~1.0 TWh of hydroelectricity production per year by 2070–2090 due to net glacier mass loss in the earlier part of the century ( [[#Schaefli--2019|Schaefli et al., 2019]] ). In the Italian Alps, under the warmest scenario of RCP8.4, up to 4% decreases in hydropower production are projected ( [[#Bombelli--2019|Bombelli et al., 2019]] ). The magnitude of change differs significantly among models. In California, USA, the average annual hydropower generation is expected to decline by 3.1% under RCP4.5 by 2040–2050, compared to the baseline 2000–2010 ( [[#Tarroja--2016|Tarroja et al., 2016]] ). In the Skagit River basin in the USA, hydropower generation is projected to increase by 19% in the winter/spring and decline by 29% in summer by the 2080s ( [[#Lee--2016|Lee et al., 2016]] ).

Apart from climate impacts on hydropower production, climate-induced flood loads and reservoir water level change may lead to dam failure under RCP2.6 and RCP4.5 scenarios ( [[#Fluixá-Sanmartín--2018|Fluixá-Sanmartín et al., 2018]] ; [[#Fluixá-Sanmartín--2019|Fluixá-Sanmartín et al., 2019]] ) ( ''medium confidence'' ). For example, the incidence of 100-year floods in the Skagit River basin in the USA and peak winter sediments are projected to increase by 49% and 335%, respectively, by 2080, necessitating fundamental changes in hydropower plant operation. Nevertheless, some risks, such as floods, will remain unmitigated even with changes in hydropower operation rules ( [[#Lee--2016|Lee et al., 2016]] ). Overall, impacts of future extreme events on energy infrastructure have been less studied than impacts of gradual changes ( [[#Cronin--2018|Cronin et al., 2018]] ). Furthermore, future hydropower development may also impact areas of high freshwater megafauna in South America, South and East Asia and in the Balkan region, and sub-catchments with a high share of threatened freshwater species are particularly vulnerable ( [[#Zarfl--2019|Zarfl et al., 2019]] ). Therefore, future hydropower dams will need to be sited carefully ( [[#Dorber--2020|Dorber et al., 2020]] ).

There is ''high confidence'' that changes in future cooling water availability are projected to affect thermoelectric production capacity negatively at global ( [[#van%20Vliet--2016b|van Vliet et al., 2016b]] ; [[#Zhou--2018b|Zhou et al., 2018b]] ) and regional scales ( [[#Bartos--2015|Bartos and Chester, 2015]] ; [[#Behrens--2017|Behrens et al., 2017]] ; [[#Ganguli--2017|Ganguli et al., 2017]] ; [[#Zhou--2018b|Zhou et al., 2018b]] ; [[#Emodi--2019|Emodi et al., 2019]] ). Global mean water temperature is projected to increase by +1°C for RCP2.6 and +2.7°C for RCP8.5 ( [[#van%20Vliet--2016b|van Vliet et al., 2016b]] ). Correspondingly, global cooling water sufficiency is projected to decline by −7.9% to −11.4% by 2040–2069 and −11.3% to −18.6% by 2070–2090 ( [[#Zhou--2018b|Zhou et al., 2018b]] ), thereby impacting thermoelectric power production.

In Asia, under a 2°C global warming scenario, coal power plants’ annual usable capacity factor in Mongolia, Southeast Asia and parts of China and India are projected to decrease due to water constraints ( [[#Wang--2019b|Wang et al., 2019b]] ). In the EU, an assessment of 1326 thermal electric plants in 818 basins projected that the number of basins with water stress would increase from 47 in 2014 to 54 in 2030 ( [[#Behrens--2017|Behrens et al., 2017]] ) with consequent impacts on cooling water supplies. In the western USA, by 2050, vulnerable power plants are projected to lose 1.1–3.0% of average summer generation capacity, which could rise to 7.2 to 8.8% loss under a 10-year drought condition ( [[#Bartos--2015|Bartos and Chester, 2015]] ). Further, 27% of thermoelectric production in the USA may be at severe risk of low-capacity utilisation due to water stress by 2030 ( [[#Ganguli--2017|Ganguli et al., 2017]] ). Thermoelectric plant capacity on the hottest summer day in the USA and EU is projected to fall by 2% under a 2°C global warming and by 3.1% under a 4°C global warming, requiring overbuilding of electricity infrastructure by 1–7% given the current energy mix portfolio ( [[#Coffel--2020|Coffel and Mankin, 2020]] ). A systematic review showed consistent decreases in mid to end of the century in thermal power production capacity due to insufficiency of cooling water in southern, western and eastern Europe ( ''high confidence'' ); North America and Oceania ( ''high confidence'' ), central, southern and western Asia ( ''high confidence'' ) and western and southern Africa ( ''medium confidence'' ) ( [[#Emodi--2019|Emodi et al., 2019]] ). Overall, apart from emissions benefits, moving away from thermal power generation to other renewable energy will also lower the chances of climate-induced curtailment of energy production ( ''high confidence'' ).

Global freshwater demand for the energy sector is projected to increase under all 2°C scenarios due to the rapid increase in electricity demand in developing countries ( [[#Fricko--2016|Fricko et al., 2016]] ). Despite the water shortage and climate change impacts, industry and energy sectors’ share in global water demand has been projected to rise to 24% by 2050 ( [[#UN%20Water--2020|UN Water, 2020]] ), which will increase the competition among various water-use sectors ( [[#Boretti--2019|Boretti and Rosa, 2019]] ). Furthermore, mining activities, which are highly dependent on sufficient water availability, are also at risk due to climate change ( [[#Aleke--2016|Aleke and Nhamo, 2016]] ). Given that some of the intensely mined regions, such as the Atacama Desert in Chile, are already water-scarce, even small changes in rainfall could destabilise water-intensive mining operations and affect the production and processing activities at mines ( [[#Odell--2018|Odell et al., 2018]] ). Overall, there is a lack of literature on the impact of climate change on future mining activities and other water-intensive industries.

In summary, globally, hydropower and thermoelectric power capacities are projected to increase and decrease, respectively, due to changes in river runoff and increases in ambient water temperatures ( ''high confidence'' ). In the future, freshwater demand for energy and industrial sectors is projected to rise significantly at the global level, triggering competition for water across sectors. Although climate change also poses risks to mining and other water-intensive industries, quantifying these risks is difficult due to limited studies.

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=== 4.5.3 Projected Risks to Water, Sanitation and Hygiene (WaSH) ===

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Climate-related extreme events impact WaSH services and local water security. While not WaSH-specific, AR5 showed that more people would experience water scarcity and floods ( ''high confidence'' ) and identified WaSH failure due to climate change as an emergent risk ( ''medium confidence'' ) leading to higher diarrhoea risk ( [[#Field--2014b|Field et al., 2014b]] ). In addition, both SR1.5 ( [[#IPCC--2018a|IPCC, 2018a]] ) and SRCCL ( [[#IPCC--2019b|IPCC, 2019b]] ) projected the risk from droughts, heavy precipitation, water scarcity, wildfire damage and permafrost degradation to be higher at 2°C warming than 1.5°C ( ''medium confidence'' ), and all these could potentially impact water quality and WaSH services.

Waterborne diseases result from complex causal relationships between climatic, environmental and socioeconomic factors that are not fully understood or modelled ( [[#Boholm--2017|Boholm and Prutzer, 2017]] ) ( ''high confidence'' ). WaSH-related health risks are related to extreme events, harmful algal blooms and WaSH practices ( [[IPCC:Wg2:Chapter:Chapter-7|Chapter 7]] WGII 7.3.2). In addition, changes in thermotolerance and chlorine resistance of certain viruses have been observed in laboratory experiments simulating different temperatures and sunlight conditions ( [[#Carratalà--2020|Carratalà et al., 2020]] ), increasing potential health risks even where traditional water treatment exists ( [[#Jiménez%20Cisneros--2014|Jiménez Cisneros et al., 2014]] ) ( ''low confidence'' ). Studies show that degraded water quality increases the willingness to pay for clean water regardless of national economic status. However, payment for clean, potable water, particularly in low- and middle-income countries, can represent a significant percentage of people’s income, limiting economic well-being and the possibility for re-investment in other livelihoods or activities ( [[#Constantine--2017|Constantine et al., 2017]] ; [[#van%20Houtven--2017|van Houtven et al., 2017]] ; [[#Price--2019|Price et al., 2019]] ).

Collectively, drinking water treatment, sanitation and hygiene interrupt disease transmission pathways, particularly for water-related diseases. However, WaSH systems themselves are vulnerable to extreme events ( [[#4.3.3|Section 4.3.3]] ). For example, sewage overflows resulting from heavy rainfall events are expected to increase waterborne disease outbreaks ( [[#Khan--2015|Khan et al., 2015]] ). High diarrhoeal disease burdens mean that small changes in climate-associated risk are projected to have significant impacts on disease burdens ( [[#Levy--2018|Levy et al., 2018]] ). For example, up to 2.2 million more cases of ''E. coli'' by 2100 in Bangladesh under a 2.1°C GWL are projected ( [[#Philipsborn--2016|Philipsborn et al., 2016]] ), while up to an 11-fold and 25-fold increase by 2050 and 2080, respectively, under a 2–4°C GWL, in disability-adjusted life years, associated with cryptosporidiosis and giardiasis in Canada is projected ( [[#Smith--2015|Smith et al., 2015]] ). In addition, an additional 48,000 deaths of children under 15 years of age globally from diarrhoea by 2030 are also projected ( [[#WHO--2014|WHO, 2014]] ). Notably, high levels of treatment compliance and boiling water before consumption offset the projected impact of climate change on giardiasis in Canada in the 2050 scenario, but could not wholly offset the projected impact in 2080 ( [[#Smith--2015|Smith et al., 2015]] ). Climate change impacts on WaSH-attributable disease burden are also projected to delay China’s progress towards disease reduction by almost 9% under RCP8.5 ( [[#Hodges--2014|Hodges et al., 2014]] ). Disruptions in the drinking water supply can lead to increased household water storage, potentially increasing vector larvae breeding habitats (see [[IPCC:Wg2:Chapter:Chapter-3#3.6.3|Section 3.6.3]] ). In combination with the projected expansion of vector ranges given climate change ( [[#Liu-Helmersson--2019|Liu-Helmersson et al., 2019]] ), there is the potential for increased risk of vector-borne disease during periods of water shortage or natural disasters ( [[#4.3.3|Section 4.3.3]] ). Moreover, energy requirements for water and wastewater treatment are indirectly responsible for GHG emissions, while the breakdown of excreta contributes directly to emissions (Box 4.5, [[#4.7.6|Section 4.7.6]] ). These contributions need to be better articulated and accounted for as part of the WaSH and climate change dialogue ( [[#Dickin--2020|Dickin et al., 2020]] ).

In summary, climate change is expected to compromise WaSH services, compounding existing vulnerabilities and increasing water-related health risks ( ''medium evidence, high agreement'' ). Therefore, additional research is required on disease-, country-, and population-specific risks due to future climate change impacts ( [[#Baylis--2017|Baylis, 2017]] ; [[#Bhandari--2020|Bhandari et al., 2020]] ; [[#Harper--2020|Harper et al., 2020]] ).

<div id="4.5.4" class="h2-container"></div>

<span id="projected-risks-to-urban-and-peri-urban-sectors"></span>
=== 4.5.4 Projected Risks to Urban and Peri-Urban Sectors ===

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AR5 reported with ''medium confidence'' that climate change would impact residential water demand, supply and management ( [[#Revi--2014|Revi et al., 2014]] ). According to AR5, water utilities are also confronted by changes to the availability of supplies, water quality and saltwater intrusion into aquifers in coastal areas due to higher ambient and water temperatures ( ''medium evidence, high agreement'' ), altered streamflow patterns, drier conditions, increased storm runoff, sea level rise and more frequent forest wildfires in catchments ( [[#Jiménez%20Cisneros--2014|Jiménez Cisneros et al., 2014]] ). SR1.5 found with ''medium confidence'' that constraining warming to 1.5°C instead of 2°C might mitigate risks for water availability, but socioeconomic drivers could affect water availability more than variations in warming levels, while the risks differ across regions ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ).

In nearly a third of the world’s largest cities, water demand may exceed surface water availability by 2050, based on RCP6.0 projections and the WaterGAP3 modelling framework ( [[#Flörke--2018|Flörke et al., 2018]] ). Under all SSPs, the global volume of domestic water withdrawal is projected to reach 700–1500 km 3 yr –1 by 2050, indicating an increase of 50 to 250%, compared to the 2010 water use intensity (400–450 km 3 yr –1 ) ( [[#Wada--2016|Wada et al., 2016]] ). Increasing water demand by cities is already spurring competition between cities and agricultural users for water, which is expected to continue ( [[#Garrick--2019|Garrick et al., 2019]] ) ( [[#4.5.1|Section 4.5.1]] ). By 2030, South and Southeast Asia are expected to have almost three quarters of the urban land under high-frequency flood risk (10.4.6). South Asia, South America and mid-latitudinal Africa are projected have the largest urban extents exposed to floods and droughts ( [[#Güneralp--2015|Güneralp et al., 2015]] ). An analysis of 571 European cities from the Urban Audit database (using RCP8.5 projections without assessing urban heat island effects) found drought conditions are expected to intensify (compared to the historical period 1951–2000) in southern European cities, particularly in Portugal and Spain ( [[#Guerreiro--2018|Guerreiro et al., 2018]] ; Section [https://www.ipcc.ch/chapter/4#CCP4.3.3 CCP4.3.3] ). Changes in river flooding are projected to affect cities in northwestern European cities and the UK between 2051 and 2100 ( [[#Guerreiro--2018|Guerreiro et al., 2018]] ) (Sections 6.2.3.2, [https://www.ipcc.ch/chapter/4#CCP2.2 CCP2.2.1] , [https://www.ipcc.ch/chapter/4#CCP2.2 CCP2.2.3] ).

Globally, climate change is projected to exacerbate existing challenges for urban water services. These challenges include population growth, the rapid pace of urbanisation and inadequate investment, particularly in less developed economies with limited governance capacity ( ''high confidence'' ) ( [[#Ceola--2016|Ceola et al., 2016]] ; [[#van%20Leeuwen--2016|van Leeuwen et al., 2016]] ; [[#Reckien--2017|Reckien et al., 2017]] ; [[#Tapia--2017|Tapia et al., 2017]] ; [[#Veldkamp--2017|Veldkamp et al., 2017]] ). More specifically, in Arusha (Tanzania), a combination of urban growth modelling, satellite imagery and groundwater modelling projected that rapid urbanisation would reduce groundwater recharge by 23–44% of 2015 levels by 2050 (under business as usual and an RCP8.5 scenario), causing groundwater levels to drop up to 75 m ( [[#Olarinoye--2020|Olarinoye et al., 2020]] ). Flood risk modelling showed a median increase in flood risk of 183% in 2030 based on baseline conditions in Jakarta (Indonesia) with flood risks increasing by up to 45% due to land use changes alone ( [[#Budiyono--2016|Budiyono et al., 2016]] ). A probabilistic analysis of surface water flood risk in London (UK) using the UKCP09 Weather Generator (with 10th and 90th percentile uncertainty bounds) found that the annual damage is expected to increase from the baseline by 101% and 128% under 2030 and 2050 high-emission scenarios, respectively ( [[#Jenkins--2018|Jenkins et al., 2018]] ).

Modified streamflow is projected to affect the amount and variability of inflow to urban storage reservoirs ( ''high confidence'' ), which may exacerbate existing challenges to urban reservoir capacity, such as sedimentation and poor water quality ( [[#Goharian--2016|Goharian et al., 2016]] ; [[#Howard--2016|Howard et al., 2016]] ; [[#Yasarer--2016|Yasarer and Sturm, 2016]] ). For example, in Melbourne (Australia), a combination of stochastic hydro-climatological modelling, rainfall-runoff modelling and climate model data projects a mean precipitation shift over catchments by −2% at 1.5°C and −3.3% at 2°C, relative to 1961–1990. Considering an annual water demand of 0.75 of the mean yearly inflow, the median water supply shortage risk was calculated to be 0.6% and 2.9% at 1.5°C and 2°C warming levels, respectively. At the higher demand level of 0.85 of the mean annual inflow, the median water shortage risk is higher, between 9.6% and 20.4% at 1.5°C and 2° C warming, respectively, without supply augmentation desalination ( [[#Henley--2019|Henley et al., 2019]] ).

As climate change poses a substantial challenge to urban water management, further refinement of urban climate models, downscaling and correction methods (e.g., [[#Gooré%20Bi--2017|Gooré Bi et al., 2017]] ; [[#Jaramillo--2018|Jaramillo and Nazemi, 2018]] ) is needed. Additionally, given that 90% of urban growth will occur in less developed regions, where urbanisation is largely unplanned ( [[#UN-Habitat--2019|UN-Habitat, 2019]] ), further research is needed to quantify the water-related risks of climate change and urbanisation on informal settlements ( [[#Grasham--2019|Grasham et al., 2019]] ; [[#Satterthwaite--2020|Satterthwaite et al., 2020]] , 4.5.3).

In summary, rapid population growth, urbanisation, ageing infrastructure and changes in water use are responsible for increasing the vulnerability of urban and peri-urban areas to extreme rainfall and drought, particularly in less developed economies with limited governance capacity ( ''high confidence'' ). In addition, modified stream flows due to climate change ( [[#4.4.3|Section 4.4.3]] ) are projected to affect the amount and variability of inflows to storage reservoirs that serve urban areas and may exacerbate challenges to reservoir capacity, such as sedimentation and poor water quality ( ''high confidence'' ).

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<span id="projected-risks-to-freshwater-ecosystems"></span>
=== 4.5.5 Projected Risks to Freshwater Ecosystems ===

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AR5 concluded that climate change is projected to be an important stressor on freshwater ecosystems in the second half of the 21st century, especially under high-warming scenarios of RCP6.0 and RCP8.5 ( ''high confidence'' ), even though direct human impacts will continue to be the dominant threat ( [[#Settele--2014|Settele et al., 2014]] ). Rising water temperatures are also projected to cause shifts in freshwater species distribution and worsen water quality problems ( ''high confidence'' ), especially in those systems that already experience high anthropogenic loading of nutrients ( [[#Settele--2014|Settele et al., 2014]] ).

Changes in precipitation and temperatures are projected to affect freshwater ecosystems and their species through, for example, direct physiological responses from higher temperatures or drier conditions or a loss of habitat for feeding or breeding ( [[#Settele--2014|Settele et al., 2014]] ; [[#Knouft--2017|Knouft and Ficklin, 2017]] ; [[#Blöschl--2019b|Blöschl et al., 2019b]] ). In addition, increased water temperatures could lead to shifts in the structure and composition of species assemblages following changes in metabolic rates, body size, timing of migration, recruitment, range size and destabilisation of food webs. A review of the impact of climate change on biodiversity and functioning of freshwater ecosystems found that under all scenarios, except the one with the lowest GHG emission scenario, freshwater biodiversity is expected to decrease proportionally to the degree of warming and precipitation alteration ( [[#Settele--2014|Settele et al., 2014]] ) '''(''' ''medium evidence'' , ''high agreement'' ''')''' .

These are several examples of such projected changes. Due to higher water temperatures, changes in macroinvertebrates and fish are projected under all future warming scenarios ( [[#Mantyka-Pringle--2014|Mantyka-Pringle et al., 2014]] ). Decreased abundance of many fish species, such as salmonids, under higher temperatures, is also projected, although the effects between species are variable ( [[#Myers--2017|Myers et al., 2017]] ). Poleward and shifts of freshwater species are projected as they try to stay within preferred cooler environmental conditions ( [[#Pecl--2017|Pecl et al., 2017]] ). Other anticipated changes include physiological adjustments with impacts on morphology with some species shrinking in body size because large surface-to-volume ratios are generally favoured under warmer conditions ( [[#Scheffers--2016|Scheffers et al., 2016]] ) and changes in species communities and food webs as a consequence of increases in metabolic rates in response to increased temperatures with the flow-on effects for many ecosystem processes ( [[#Woodward--2010|Woodward et al., 2010]] ). Changes in the seasonality of flow regimes and variability ( [[#Blöschl--2019b|Blöschl et al., 2019b]] ) and more intermittent flows ( [[#Pyne--2017|Pyne and Poff, 2017]] ) are also projected and could result in decreased food chain lengths through the loss of large-bodied top predators ( [[#Sabo--2010|Sabo et al., 2010]] ) and changes in nutrient loadings and water quality ( [[#Woodward--2010|Woodward et al., 2010]] ). The impacts on freshwater systems in drylands are projected to be more severe ( [[#Jaeger--2014|Jaeger et al., 2014]] ; [[#Gudmundsson--2016|Gudmundsson et al., 2016]] ). Changes to snow and glacier melting, including the complete melting of some glaciers ( [[#Leadley--2014|Leadley et al., 2014]] ; [[#Kraaijenbrink--2017|Kraaijenbrink et al., 2017]] ), are projected to reduce water availability and cause declines in biodiversity in high altitudes through local extirpations and species extinctions in regions of high endemism. Lake nutrient dynamics are expected to change, for example, at 2°C warming, and net increase in CH 4 emissions by 101–183% in hypereutrophic lakes and 47–56% in oligotrophic lakes in Europe are projected ( [[#Sepulveda-Jauregui--2018|Sepulveda-Jauregui et al., 2018]] ). Similarly, under the high-GHG emission scenario, lake stratification is projected to begin 22.0 ± 7.0 d earlier and end 11.3 ± 4.7 d later by the end of this century ( [[#Woolway--2021|Woolway et al., 2021]] ). While overall future trends on climate change on freshwater species and habitats are largely negative, evidence indicates that different species are projected to respond at different rates, with interactions between species expected to be disrupted and which may result in novel biological communities and rapid change in ecological processes and functions ( [[#Pecl--2017|Pecl et al., 2017]] ).

These impacts are expected to be most noticeable where significant air temperature increases are projected, leading to local or regional population extinctions for cold-water species because of range shrinking, especially under the RCP4.5, 6.0 and 8.5 scenarios ( [[#Comte--2017|Comte and Olden, 2017]] ). The consequences for freshwater species are projected to be severe with local extinctions as the freshwater ecosystems dry. In the Americas, under all scenarios that have been examined, the risk of extinction of freshwater species is projected to increase above that already occurring levels due to biodiversity loss caused by pollution, habitat modification, over-exploitation and invasive species ( [[#IPBES--2019|IPBES, 2019]] ). Freshwater ecosystems are also at risk of abrupt and irreversible change, especially those in the higher latitudes and altitudes with significant changes in species distributions, including those induced by melting permafrost systems ( [[#Moomaw--2018|Moomaw et al., 2018]] ; [[#IPBES--2019|IPBES, 2019]] ).

While changes in the species distribution across freshwater ecosystems are projected, the extent of change and the ability of individual species or populations to adapt are not widely known. Species that cannot move to more amenable habitats may become extinct, whereas those who migrate may relocate. An unknown outcome could be establishing novel ecosystems with new assemblages of species, including invasive alien species, in response to changes in the environment with the prospect of irreversible changes in freshwater ecosystems ( [[#Moomaw--2018|Moomaw et al., 2018]] ).

In summary, changes in precipitation and temperatures are projected to affect all types of freshwater ecosystems and their species. Under all scenarios, except the one with the lowest GHG emission scenario, freshwater biodiversity is expected to decrease proportionally to the degree of warming and precipitation change ( ''medium evidence, high agreement'' ).

<div id="4.5.6" class="h2-container"></div>

<span id="projected-risks-to-water-related-conflicts"></span>
=== 4.5.6 Projected Risks to Water-Related Conflicts ===

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AR5 concluded with ''medium confidence'' that climate change can indirectly increase the risks of violent conflicts, though the link to hydrological changes were not spelled out ( [[#Jiménez%20Cisneros--2014|Jiménez Cisneros et al., 2014]] ). Furthermore, according to IPCC SR1.5 ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ), if the world warms by 2°C–4°C by 2050, rates of human conflict could increase, but again, the role of hydrological change in this was not explicit ( ''medium confidence'' ).

The impact of climate change on shared water resources might increase tensions among states, particularly in the absence of strong institutional capacity ( [[#Petersen-Perlman--2017|Petersen-Perlman et al., 2017]] ; [[#Dinar--2019|Dinar et al., 2019]] ). On the other hand, although the mere existence of formal agreements does not necessarily reduce the risks of conflicts, robust treaties and institutions can promote cooperative events, even under hydrological stress ( [[#Link--2016|Link et al., 2016]] ) ''.'' Yet, since both conflictive and cooperative events are possible under conditions of climatic variability, whether conflict arises or increases depends on several contextual socioeconomic and political factors, including the adaptive capacity of the riparian states ( [[#Koubi--2019|Koubi, 2019]] ), the existence of power asymmetries ( [[#Dinar--2019|Dinar et al., 2019]] ) and pre-existing social tensions ( ''medium confidence'' ).

At the intra-state level, analysis suggests that additional climate change will increase the probability of conflict risks, with 13% increase probability at the 2°C GWL and 26% probability at the 4°C GWL scenario ( [[#Mach--2019|Mach et al., 2019]] ). However, to date, other factors are considered more influential drivers of conflict, including lack of natural resource use regulations ( [[#Linke--2018b|Linke et al., 2018b]] ), societal exclusion ( [[#von%20Uexkull--2016|von Uexkull et al., 2016]] ; [[#van%20Weezel--2019|van Weezel, 2019]] ), poor infrastructures and a history of violent conflict ( [[#Detges--2016|Detges, 2016]] ) ( ''high confidence'' ). In addition, ''medium-high evidence'' exists that climate change imposes additional pressures on regions that are already fragile and conflict-prone ( [[#Matthew--2014|Matthew, 2014]] ; [[#Earle--2015|Earle et al., 2015]] ) ( ''medium agreement'' ).

Recent research indicates that climatic change can multiply tensions in regions dependent on agriculture when coupled with other socioeconomic and political factors ( [[#Koubi--2019|Koubi, 2019]] ), including a low level of human development ( [[#Ide--2020|Ide et al., 2020]] ) and deterioration of individual living conditions ( [[#Vestby--2019|Vestby, 2019]] ). On the other side, intergroup cohesion ( [[#De%20Juan--2020|De Juan and Hänze, 2020]] ) and policies that improve societal development and good governance reduce the risk of conflict associated with the challenges to adaptation to climate change ( [[#Hegre--2016|Hegre et al., 2016]] ; [[#Witmer--2017|Witmer et al., 2017]] ) ( ''medium confidence'' ) at both the intra-state and inter-state level.

Increased risk of conflict between different sectors (agriculture, industry, domestic) and needs (urban, rural) is projected to arise in several river basins due to climate change and socioeconomic developments, including urbanisation ( [[#Flörke--2018|Flörke et al., 2018]] ). Future climatic conditions and population growth are expected to exert additional pressures on managing already stressed basins such as the Nile, the Indus, Colorado, the Feni, the Irrawaddy, the Orange and the Okavango ( [[#Farinosi--2018|Farinosi et al., 2018]] ). In addition, recent scenario analysis in global transboundary basins supports the finding that there is more potential for conflict in areas already under water stress, such as central Asia and the northern parts of Africa ( [[#Munia--2020|Munia et al., 2020]] ) ( ''medium confidence'' ).

In summary, the impact of climate change on water resources might increase tensions, particularly in the absence of strong institutional capacity. However, whether conflict arises or increases depends on several contextual socioeconomic and political factors. Evidence exists that climate change imposes additional pressures on regions already under water stress or fragile and conflict-prone ( ''medium confidence'' ).

<div id="4.5.7" class="h2-container"></div>

<span id="projected-risks-to-human-mobility-and-migration"></span>
=== 4.5.7 Projected Risks to Human Mobility and Migration ===

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SR1.5 found with ''medium confidence'' that migration is expected to increase with further warming, but that there are major knowledge gaps preventing more detailed assessments ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). However, as in AR5, there was no specific focus on hydrological changes-induced migration.

In general, the projected population growth in at-risk areas, especially in low-income countries, is expected to increase future migration and displacement ( [[#McLeman--2016|McLeman et al., 2016]] ; [[#Rigaud--2018|Rigaud et al., 2018]] ). For example, a study looking at potential flood exposure found that low-income countries, particularly in Africa, are at higher risk for flood-induced displacement ( [[#Kakinuma--2020|Kakinuma et al., 2020]] ). One model, focusing on slow-onset climate impacts, such as water stress, crop failure and sea level rise, projected between 31–72 million people (RCP2.6, SSP4) and 90–143 million people (RCP8.5, SSP4) internally displaced by 2050 in sub-Saharan Africa, South Asia and Latin America ( [[#Rigaud--2018|Rigaud et al., 2018]] ). Another estimate, incorporating temperature increase and precipitation, projects that asylum applications to the EU could increase by between 0.098 million (RCP4.5) and 0.66 million (RCP8.5) yr –1 , as a consequence of temperature increases in agricultural areas of low-income countries ( [[#Missirian--2017|Missirian and Schlenker, 2017]] ) ( ''limited evidence; medium agreement'' ).

More detailed local and regional models are needed, incorporating migrant destinations ( [[#Abel--2019|Abel et al., 2019]] ) and immobility ( [[#Zickgraf--2018|Zickgraf, 2018]] ).

In summary, research that projects future migration changes due to climate-induced hydrological changes is ''limited'' and shows significant uncertainties about the number of migrants and their destinations ( ''limited evidence; medium agreement'' ).

<div id="4.5.8" class="h2-container"></div>

<span id="projected-risks-to-the-cultural-water-uses-of-indigenous-peoples-local-communities-and-traditional-peoples"></span>
=== 4.5.8 Projected Risks to the Cultural Water Uses of Indigenous Peoples, Local Communities and Traditional Peoples ===

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AR5 found that climate change will threaten cultural practices and values, although the risks vary across societies and over time ( ''medium evidence, high agreement'' ). Furthermore, AR5 concluded that significant changes in the natural resource base on which many cultures depend would directly affect the cultural core, worldviews, cosmologies and symbols of indigenous cultures ( [[#Adger--2014|Adger and Pulhin, 2014]] ). SR1.5 concluded with ''high confidence'' that limiting global warming to 1.5°C, rather than 2°C, will strongly benefit terrestrial and wetland ecosystems and their services, including the cultural services provided by these ecosystems ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). SROCC found with ''high confidence'' that cultural assets are projected to be negatively affected by future cryospheric and associated hydrological changes ( [[#Hock--2019b|Hock et al., 2019b]] ).

There is ''high confidence'' that the cultural water uses of Indigenous Peoples, local communities and traditional peoples are at risk of climate change-related hydrological change (Table 4.7). Climate-driven variations in streamflow, saltwater intrusion and projected increases in water temperature will exacerbate declines of culturally important species and lead to variations or depletion of culturally important places and subsistence practices. For example, in New Zealand, the increasing risk of flood events may impact culturally important fish species for M ''ā'' ori ( [[#Carter--2019|Carter, 2019]] ), while habitat changes may shift the distribution of culturally significant plants ( [[#Bond--2019|Bond et al., 2019]] ). In Australia, Yuibera and Koinmerburra Traditional Owners fear the saltwater inundation of culturally significant sites and waterholes ( [[#Lyons--2019|Lyons et al., 2019]] ), while the flooding of culturally significant wetlands will negatively affect the Lumbee Tribe (USA) ( [[#Emanuel--2018|Emanuel, 2018]] ). Moreover, changes in the carrying capacity of ice, snow quality and formation will probably increase the physical risks to Saami practising reindeer herding ( [[#Jaakkola--2018|Jaakkola et al., 2018]] ).

'''Table 4.7 |''' Selected projected risks to Indigenous Peoples’ uses of water.

{| class="wikitable"
|-
! Region

! Indigenous People

! Climate hazard

! Water-related risk

! Situated knowledge

! Reference

|-
| Asia

| Ifugao

| Increased temperatures; increasing rainfall (wet season); decreasing rainfall (dry season)

| Flooding (wet season); water deficit (dry season)

| Increases in future wet season rainfall pose increase risks of excess surface water runoff and potential for soil erosion, which may cause the collapse of Ifugao rice terraces. Reductions in future dry season rainfall and warmer temperatures indicate significant water deficits during the growing season of local ''tinawon'' rice.

| [[#Soriano--2020|Soriano and Herath (2020)]]

|-
| Australasia

| Yuibera and Koinmerburra Traditional Owner groups

| Sea-level rise

| Flooding

| Culturally important coastal waterholes, wetlands and sites are at risk of saltwater inundation due to rising sea levels. If inundated, Traditional Owners may not be able to maintain cultural connections to these important sites (11.4.1).

| Lyons (2019)

|-
| Australasia

| M ''ā'' ori

| Increased precipitation

| Flooding

| Increasing flood events may negatively impact spawning and fishing sites of the culturally important īnaka (whitebait; ''Galaxias maculates'' ) in the Waikōuaiti River (11.4.2).

| [[#Carter--2019|Carter (2019)]]

|-
| Australasia

| M ''ā'' ori

| Increased temperature; precipitation variability

| Ecosystem

change

| Changes in temperature and precipitation are projected to shift the range of wetland plants (Kūmarahou and Kuta) in New Zealand, which may decrease access to these culturally significant species, which are used for medicinal and weaving purposes. The changing distribution of these plants may lead to a loss of Indigenous knowledge and affect inter-tribal reciprocity and gifting practices (11.4.2).

| [[#Bond--2019|Bond et al. (2019)]]

|-
| Central and South America

| Warao

| Sea level rise

| Flooding

| The partial or total inundation of the Orinoco Delta will result in the loss of freshwater wetlands and species, which will produce rapid shifts in the culturally significant lands and resources of the Warao. Among the affected species is the Mauritia palm, on which Warao culture and livelihoods are based.

| [[#Vegas-Vilarrúbia--2015|Vegas-Vilarrúbia et al. (2015)]]

|-
| Europe

| Saami

| Increased temperatures; changes in precipitation

| Winter thaw

| Reindeer herding is culturally important for Saami and provides a means to maintain traditions, language and cultural identity, thus constituting an essential part of Saami physical and mental well-being. More frequent ice formation on soil and snow, which will reduce the availability and quality of winter forage for reindeer, will negatively impact reindeer herding and thus Saami identity and well-being (13.8.1.2).

| Jaakkola et al. (2018); (Markkula et al. (2019)

|-
| North America

| Lumbee Tribe

| Increased temperatures; increased rainfall variability

| Flooding

| Climate-related degradation and flooding of wetlands and streams in the Lumbee River watershed will negatively affect cultural practices of fishing and harvesting that rely on access to and resources obtained from the area.

| [[#Emanuel--2018|Emanuel (2018)]]

|}

Further research is necessary to assess the extent and nature of climate-driven risks to cultural water uses in the context of broader socioeconomic, cultural and political challenges facing diverse Indigenous Peoples and local and traditional communities. In addition, given the significance of IKLK to adaptive capacity and community-led adaptation, the potential risks of climate-related hydrological changes to diverse cultural water uses warrant closer study (Sections 4.6.9, 4.8.4, Cross-Chapter Box INDIG in Chapter 18).

In sum, there is ''high confidence'' that climate-driven hydrological changes to cultural water uses and culturally significant ecosystems and species are projected to pose risks to the physical well-being of Indigenous Peoples, local communities and traditional peoples.

<div id="4.6" class="h1-container"></div>

<span id="key-risks-and-adaptation-responses-in-various-water-use-sectors"></span>