Editing IPCC:AR6/WGIII/Chapter-6 (section)

==== 6.5.2.1 dropower ====

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The impacts of climate change on hydropower will vary by region. High latitudes in the northern hemisphere are anticipated to experience increased runoff and hydropower potential. For other regions, studies find both increasing and decreasing runoff and hydropower potential. Areas with decreased runoff are anticipated to experience reduced hydropower production and increased water conflict among different economic activities ( ''high confidence'' ).

Hydropower production is directly related to the availability of water. Changes in runoff and its seasonality and changes in temperature and precipitation intensity will influence hydroelectricity production ( [[#IHA--2019|IHA 2019]] ). In general, increased precipitation will increase water availability and hydropower production. Increased precipitation intensity, however, may impact on the integrity of dam structures and affect power production by increasing debris accumulation and vegetation growth. Additionally, increased precipitation intensity results in the silting of the reservoirs or increases the amount of water spilt, resulting in erosion ( [[#Schaeffer--2012|Schaeffer et al. 2012]] ; [[#IHA--2019|IHA 2019]] ). Climate change will likely lead to higher air temperatures, resulting in more surface evaporation, less water storage, and loss of equipment efficiency ( [[#Ebinger--2011|Ebinger and Vergara 2011]] ; [[#Mukheibir--2013|Mukheibir 2013]] ; [[#Fluixá-Sanmartín--2018|Fluixá-Sanmartín et al. 2018]] ; [[#Hock--2019|Hock et al. 2019]] ). Climate change may alter the demands for water use by other sectors that often rely on stored water in multi-purpose reservoirs, and may therefore generate conflicts over water use. The increased need for water for irrigation and/or industry can affect the availability of water for hydropower generation ( [[#Spalding-Fecher--2016|Spalding-Fecher et al. 2016]] ; [[#Solaun--2017|Solaun and Cerdá 2017]] ). Higher temperatures increase glacier melt, increasing water availability for hydropower while the glaciers exist. Changes in the timing of snow and ice melt may require upgrading in storage capacity and adaptation of the hydropower plant management for fully exploiting the increase in water availability.

The conclusions regarding climate change impacts on hydropower vary due to differences in modelling assumptions and methodology, such as choice of the climate and hydrological models, choice of metrics (e.g., projected production vs hydropower potential), level of modelling details between local and global studies, reservoir operation assumptions. Also important is how hydropower production matches up with other reservoir purposes, accounting for other water and energy users, and how the competing uses are impacted by climate change ( [[#van%20Vliet--2016b|van Vliet et al. 2016b]] ; [[#Turner--2017|Turner et al. 2017]] ). Nonetheless, analyses consistently demonstrate that the global impact of climate change on hydropower will be small, but the regional impacts will be larger, and will be both positive and negative (Figure 6.20). Gross global hydropower potential in the 2050s has been estimated to slightlydecrease ( [[#Hamududu--2012|Hamududu and Killingtveit 2012]] ) between 0.4% (for the low-emission scenario) and 6.1% (for the highest-emission scenario) for the 2080s compared to 1971–2000 ( [[#van%20Vliet--2016a|van Vliet et al. 2016a]] ).

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'''Figure 6.20 | Global spatial patterns of changes in gross hydropower potential based on climate forcing from five climate models.''' Changes are shown for the 2050s (upper) and the 2080s (lower) for the low-emission scenario (RCP2.6; left) and highest emission scenario (RCP8.5; right) scenarios relative to the control period (1971–2000). Source: data from [[#van%20Vliet--2016b|van Vliet et al. (2016b)]] .

Regional changes in hydropower are estimated from 5–20% increases for most areas in high latitudes ( [[#van%20Vliet--2016b|van Vliet et al. 2016b]] ; [[#Turner--2017|Turner et al. 2017]] ) to decreases of 5–20% in areas with increased drought conditions ( [[#Cronin--2018|Cronin et al. 2018]] ). Models show a consistent increase in streamflow and hydropower production by 2080 in high latitudes of the northern hemisphere and parts of the tropics (Figure 6.20) (e.g., central Africa and southern Asia) while decreasing in the USA, southern and central Europe, Southeast Asia and southern South America, Africa and Australia ( [[#van%20Vliet--2016c|van Vliet et al. 2016c]] ,a). Decreases in hydropower production are indicated for parts of North America, central and southern Europe, the Middle East, central Asia and Southern South America. Studies disagree on the changes in hydropower production in China, central South America, and partially in southern Africa ( [[#Hamududu--2012|Hamududu and Killingtveit 2012]] ; [[#van%20Vliet--2016b|van Vliet et al. 2016b]] ; [[#Solaun--2019|Solaun and Cerdá 2019]] ; [[#Fan--2020|Fan et al. 2020]] ).

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