Editing IPCC:AR6/SROCC/Chapter-2 (section)

==== 2.3.1.3 Key Impacts and Vulnerability ====

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<span id="hydropower"></span>
===== 2.3.1.3.1 Hydropower =====

Hydropower comprises about 16% of electricity generation globally but close to 100%, in many mountainous countries (Hamududu and Killingtveit, 2012 <sup>[[#fn:r316|316]]</sup> ; IHA, 2018). It represents a significant source of revenue for mountainous regions (Gaudard et al., 2016 <sup>[[#fn:r317|317]]</sup> ). Due to the dependence on water resources as key input, hydropower operations are expected to be affected by changes in runoff from glaciers and snow cover (Section 2.3.1.1, FAQ 2.1). Both increases and decreases in annual and/or seasonal water input to hydropower facilities have been recorded in several high mountain regions, for example, in Switzerland (Hänggi and Weingartner, 2012 <sup>[[#fn:r318|318]]</sup> ; Schaefli et al., 2019 <sup>[[#fn:r319|319]]</sup> ), Canada (Jost et al., 2012 <sup>[[#fn:r320|320]]</sup> ; Jost and Weber, 2013 <sup>[[#fn:r321|321]]</sup> ), Iceland (Einarsson and Jónsson, 2010 <sup>[[#fn:r322|322]]</sup> ) and High Mountain Asia (Ali et al., 2018 <sup>[[#fn:r323|323]]</sup> ). However, there is only ''limited evidence'' ( ''medium agreement'' ) that changes in runoff have led to changes in hydropower plant operation. For example, in Iceland, the National Power Company observed in 2005 that flows into their energy system were greater than historical flows. By incorporating the most recent runoff data into strategies for reservoir management it was possible to increase production capacity (Braun and Fournier, 2016 <sup>[[#fn:r324|324]]</sup> ).

There is ''robust evidence (medium agreement'' ) that water input to hydropower facilities will change in the future due to cryosphere-related impacts on runoff (Section 2.3.1.1). For example, in the Skagit river basin in British Columbia and Northern Washington (Lee et al., 2016 <sup>[[#fn:r325|325]]</sup> ) and in California (Madani and Lund, 2010 <sup>[[#fn:r326|326]]</sup> ) projections (SRES A1B) show more runoff in winter and less in summer. In India, snow and glacier runoff to hydropower plants is projected to decline in several basins (Ali et al., 2018 <sup>[[#fn:r327|327]]</sup> ). In some cases, catchments that are close together are projected to evolve in contrasting directions in terms of runoff, for example in the European Alps (Gaudard et al., 2013 <sup>[[#fn:r328|328]]</sup> ; Gaudard et al., 2014 <sup>[[#fn:r329|329]]</sup> ). Increased runoff due to changes in the cryosphere will increase the risk of overflows (non-productive discharge), particularly during winter and spring melt, with the greatest impacts on run-of-river power plants (e.g., in Canada; Minville et al., 2010 <sup>[[#fn:r330|330]]</sup> ; Warren and Lemmen, 2014 <sup>[[#fn:r331|331]]</sup> ) ( ''medium confidence'' ).

There is ''medium evidence'' ( ''high agreement'' ) that changes in glacier- and moraine-dammed lakes, and changes in sediment supply will affect hydropower generation (Colonia et al., 2017 <sup>[[#fn:r332|332]]</sup> ; Hauer et al., 2018 <sup>[[#fn:r333|333]]</sup> ). Many glacier lakes have increased in volume, and can damage hydropower infrastructure when they empty suddenly (Engeset et al., 2005 <sup>[[#fn:r334|334]]</sup> ; Jackson and Ragulina, 2014 <sup>[[#fn:r335|335]]</sup> ; Carrivick and Tweed, 2016 <sup>[[#fn:r336|336]]</sup> ) (Section 2.3.2). If large enough, hydropower reservoirs can reduce the downstream negative impacts of changes in the cryosphere by storing and providing freshwater during hot, dry periods or by alleviating the effects of glacier floods (Jackson and Ragulina, 2014 <sup>[[#fn:r337|337]]</sup> ; Colonia et al., 2017 <sup>[[#fn:r338|338]]</sup> ). In mountain rivers, sediment volume and type depend on connectivity between hillslopes and the valley floor (Carrivick et al., 2013 <sup>[[#fn:r339|339]]</sup> ), glacier activity (Lane et al., 2017 <sup>[[#fn:r340|340]]</sup> ) and on water runoff regime feedbacks with river channel dynamics (Schmidt and Morche, 2006 <sup>[[#fn:r341|341]]</sup> ). An increase in suspended sediment loading under current reservoir operating policies is projected for some hydropower facilities, for example, in British Columbia and Northern Washington (Lee et al., 2016 <sup>[[#fn:r342|342]]</sup> ).

Only a few studies have addressed the economic effects on hydropower due directly to changes in the cryosphere. For example in Peru, Vergara et al. (2007) studied the effect of both reduced glacier runoff and runoff with no glacier input once the glaciers have completely melted for the Cañón del Pato hydropower plant in Peru, and found an economic cost of between 5 – 20 million USD yr -1 , with the lower figure for the cost of energy paid to the producer and the higher figure the society cost. Costs calculated for all of Peru, where ~80% of electricity comes from hydropower range from 60 – 212 million USD yr -1 . If the cost of rationing energy is considered, the national cost is estimated as 1,500 million USD yr -1 .

Other factors than changes in the cryosphere, such as market policies and regulation, may have greater significance for socioeconomic development of hydropower in the future (Section 2.3.1.4, Gaudard et al., 2016). Hence, despite the efforts of hydropower agencies and regulatory bodies to quantify changes or to develop possible adaptation strategies (IHA, 2018), only a few organisations are incorporating current knowledge of climate change into their investment planning. The World Bank uses a decision tree approach to identify potential vulnerabilities in a hydropower project incurred from key uncertain factors and their combinations (Bonzanigo et al., 2015 <sup>[[#fn:r343|343]]</sup> ).

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<span id="agriculture"></span>
===== 2.3.1.3.2 Agriculture =====

High mountains have supported agricultural livelihoods for centuries. Rural communities are dependent on adequate levels of soil moisture at planting time, derived in part in many cases from irrigation water which includes glacier and snowmelt water; as a result, they are exposed to risk which stems from cryosphere changes ( ''high confidence'' ) (Figure 2.8). The relative poverty of many mountain communities contributes to their vulnerability to the impacts of these cryosphere changes (McDowell et al., 2014 <sup>[[#fn:r344|344]]</sup> ; Carey et al., 2017 <sup>[[#fn:r345|345]]</sup> ; Rasul and Molden, 2019 <sup>[[#fn:r346|346]]</sup> ) ''(medium evidence, high agreement).'' Glacier and snowmelt water contribute irrigation water to adjacent lowlands as well. Pastoralism, an important livelihood strategy in mountain regions, is also impacted by cryosphere changes, but described in Section 2.3.7.

There is ''medium evidence (medium agreement)'' that reduction in streamflow due to glacier retreat or reduced snow cover has led to reduced water availability for irrigation of crops and declining agricultural yields in several mountain areas (Table SM2.11), for example in the tropical Andes (e.g., Bury et al., 2011) and High Mountain Asia (e.g., Nüsser and Schmidt, 2017). In the Southern Andes, increased streamflow in the Elqui River in Chile, due to glacier retreat or changing snow cover, has led to increased water availability for irrigation and increased agricultural yields (Young et al., 2010 <sup>[[#fn:r347|347]]</sup> ).

In addition to the effects on agriculture of changing availability of irrigation water, reductions in snow cover can also impact agriculture through its direct effects on soil moisture, as reported for Nepal, where lesser snow cover has led to the drying of soils and lower yields of potatoes and fodder (Smadja et al., 2015 <sup>[[#fn:r348|348]]</sup> ). Agriculture in high mountain areas is sensitive to other climatic drivers as well. Rising air temperatures increase crop evapotranspiration, thus increasing water demand for crop production to maintain optimal yield (Beniston and Stoffel, 2014 <sup>[[#fn:r349|349]]</sup> ). They are also associated with upslope movement of cropping zones, which favours some farmers in high mountain areas, who are increasingly able to cultivate new crops, such as onions, garlic and apples in Nepal (Huntington et al., 2017 <sup>[[#fn:r350|350]]</sup> ; Hussain et al., 2018 <sup>[[#fn:r351|351]]</sup> ), and maize in Ecuador (Skarbø and VanderMolen, 2014 <sup>[[#fn:r352|352]]</sup> ). Dry spells and unseasonal frosts have also impacted agriculture in Peru (Bury et al., 2011 <sup>[[#fn:r353|353]]</sup> ).

Adaptation activities in mountain agriculture related at least partially to cryospheric changes are detailed in Table SM2.12 and their geographic spread shown in Figure 2.9. Agriculture in these areas is sensitive to non-climate drivers as well, such as market forces and political pressures (Montana et al., 2016 <sup>[[#fn:r354|354]]</sup> ; Sietz and Feola, 2016 <sup>[[#fn:r355|355]]</sup> ; Figueroa-Armijos and Valdivia, 2017 <sup>[[#fn:r356|356]]</sup> ) and shifts in water governance (Rasmussen, 2016). The majority of the adaptation activities are autonomous, though some are planned or carried out with support from national governments, non-governmental organisations (NGOs), or international aid organisations. Though many studies report on benefits from these activities which accrue to community members as increased harvests and income, systematic evaluations of these adaptation strategies are generally lacking. A range of factors, discussed below, place barriers which limit the scale and scope of these activities in the mountain agricultural sector, including a lack of finance and technical knowledge, low adaptive capacity within communities, ill-equipped state organisations, ambiguous property rights and inadequate institutional and market support ( ''medium evidence, high agreement'' ). Section 2.3.7 examines two other responses to decreasing irrigation water: wage labour migration, which often serves as an adaptation strategy, and displacement of entire communities, an indication of the limits to adaptation — this displacement is also due in some cases to natural hazards.

To cope with the reduced water supplies, planted areas have been reduced in a number of different places in Nepal (Gentle and Maraseni, 2012 <sup>[[#fn:r358|358]]</sup> ; Sujakhu et al., 2016 <sup>[[#fn:r359|359]]</sup> ). Adaptation responses within irrigation systems include the adoption of new irrigation technologies or upgrading existing technologies, adopting water conservation measures, water rationing, constructing water storage infrastructure, and change in cropping patterns (Rasul et al., 2019 <sup>[[#fn:r360|360]]</sup> ; Figure 2.9). Water delivery technologies which reduce loss are adopted in Chile (Young et al., 2010 <sup>[[#fn:r361|361]]</sup> ) and Peru (Orlove et al., 2019 <sup>[[#fn:r362|362]]</sup> ). Similarly, greenhouses have been adopted in Nepal (Konchar et al., 2015 <sup>[[#fn:r363|363]]</sup> ) to reduce evapotranspiration and frost damage, though limited access to finance is a barrier to these activities. Box 2.3 describes innovative irrigation practices in India. Local pastoral communities have responded to these challenges with techniques broadly similar to those in agricultural settings by expanding irrigation facilities, for example, in Switzerland (Fuhrer et al., 2014 <sup>[[#fn:r364|364]]</sup> ). In addition to adopting new technologies, some water users make investments to tap more distant sources of irrigation water. Cross-Chapter Box 3 in Chapter 1 discusses such efforts in Northern Pakistan, where landslides, associated with cryosphere change, have also damaged irrigation systems.

The adoption of new crops and varieties is an adaptation response found in several regions. Farmers in northwest India have increased production of lentils and vegetables, which provide important nutrients to the local diet, with support from government watershed improvement programs which help address decreased availability of irrigation water, though stringent requirements for participation in the programs have limited access by poor households to this assistance (Dame and Nüsser, 2011 <sup>[[#fn:r365|365]]</sup> ). Farmers who rely on irrigation in the Naryn River basin in Kyrgyzstan have shifted from the water intensive fruits and vegetables to fodder crops such as barley and alfalfa, which are more profitable. Upstream communities, with greater access to water and more active local institutions, are more willing to experiment with new crops than those further downstream (Hill et al., 2017 <sup>[[#fn:r366|366]]</sup> ). In other areas, crop choices also reflect responses to rising temperatures along with new market opportunities such as the demand for fresh vegetables by tourists in Nepal (Konchar et al., 2015 <sup>[[#fn:r367|367]]</sup> ; Dangi et al., 2018 <sup>[[#fn:r368|368]]</sup> ) and the demand for roses in urban areas in Peru (SENASA, 2017 <sup>[[#fn:r369|369]]</sup> ). Indigenous knowledge and local knowledge (Cross-Chapter Box 4 in Chapter 1), access to local and regional seed supply networks, proximity to agricultural extension and support services also facilitate the adoption of new crops (Skarbø and VanderMolen, 2014 <sup>[[#fn:r370|370]]</sup> ).

Local institutions and embedded social relations play a vital role in enabling mountain communities to respond to the impacts of climate driven cryosphere change. Indigenous pastoral communities who have tapped into new water sources to irrigate new areas in Peru have also strengthened the control of access to existing irrigated pastures (Postigo, 2014 <sup>[[#fn:r371|371]]</sup> ) and Bolivia (Yager, 2015 <sup>[[#fn:r372|372]]</sup> ). In an example of indigenous populations in the USA, two tribes who share a large reservation in the Northern Rockies rely on rivers which receive glacier melt water to irrigate pasture, and maintain fisheries, domestic water supplies, and traditional ceremonial practices. Tribal water managers have sought to install infrastructure to promote more efficient water use and protect fisheries, but these efforts have been impeded by land and water governance institutions in the region and by a history of social marginalisation (McNeeley, 2017 <sup>[[#fn:r373|373]]</sup> ).

High mountain communities have sought new financial resources from wage labour (Section 2.3.7), tourism (Mukherji et al., 2019 <sup>[[#fn:r374|374]]</sup> ) and government sources to support adaptation activities. Local water user associations in Kyrgyzstan and Tajikistan have adopted less water intensive crops and reorganised the use and maintenance of irrigation systems, investing government relief payments after floods (Stucker et al., 2012 <sup>[[#fn:r375|375]]</sup> ). Similar measures are reported from India and Pakistan (Dame and Mankelow, 2010 <sup>[[#fn:r376|376]]</sup> ; Clouse, 2016 <sup>[[#fn:r377|377]]</sup> ; Nüsser and Schmidt, 2017 <sup>[[#fn:r378|378]]</sup> ), Nepal (McDowell et al., 2013 <sup>[[#fn:r379|379]]</sup> ) and Peru (Postigo, 2014 <sup>[[#fn:r380|380]]</sup> ). In contrast, fewer adaptation measures have been adopted in Uzbekistan, due to low levels of capital availability and to agricultural policies, including centralised water management, crop production quotas and weak agricultural extension, which limit the response capacity of farmers (Aleksandrova et al., 2014 <sup>[[#fn:r381|381]]</sup> ).

Lowland agricultural areas which receive irrigation water from rivers fed by glacier melt and snowmelt are projected to face negative impacts in some regions ( ''limited evidence, high agreement'' ). In the Rhone basin in Switzerland, many irrigated pasture areas are projected to face water deficits by 2050, under the A1B scenario (Fuhrer et al., 2014 <sup>[[#fn:r382|382]]</sup> ; Cross Chapter Box 1 in Chapter 1). For California and the southwestern USA, a shift to peak snowmelt earlier in the year would create more frequent floods, and a reduced ability of existing reservoirs to store water by 2050 under RCP8.5 (Pagán et al., 2016 <sup>[[#fn:r383|383]]</sup> ) and by 2100 under RCP2.6, RCP4.5 and RCP8.5 (Pathak et al., 2018 <sup>[[#fn:r374|374]]</sup> ). The economic values of these losses have been estimated at 10.8 – 48.6 billion USD by around 2050 (Sturm et al., 2017 <sup>[[#fn:r385|385]]</sup> ). A similar transition to runoff peaks earlier in the year by 2100 under RCP2.6, RCP4.5 and RCP8.5, creating challenges for management of irrigation water, has been reported for the countries in central Asia which are dependent on snow cover and glaciers of the Tien Shan (Xenarios et al., 2018 <sup>[[#fn:r386|386]]</sup> ). In India and Pakistan, where over 100 million farmers receive irrigation from the Indus and Ganges Rivers, which also have significant inputs from glaciers and snowmelt, also face risks of decreasing water supplies from cryosphere change by 2100 (Biemans et al., 2019 <sup>[[#fn:r387|387]]</sup> ; Rasul and Molden, 2019 <sup>[[#fn:r388|388]]</sup> ).

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