5

Conclusion

The climate and hydrology of the HKH region are changing. There are many important uncertainties about the current state of physical and social systems in the region in addition to the uncertainties about the future. However, not everything is uncertain or unknown. It is important to consider the impact of glacial retreat on regional water resources in the larger, hydroclimatic and social context of the HKH region. The effects of climate changes on glacier dynamics will affect both the supply and demand for water in the Himalayan region, and these changes will, in turn, affect the vulnerability of key populations to freshwater problems. Glacial retreat is only one factor that contributes to changes in the hydrological cycle, and the relative importance of glacial meltwater varies across the region and between seasons. In most instances, the contribution to surface-water discharge of snowmelt exceeds that of glacial melt. Glacial melt does contribute to the water flow in major rivers such as the Ganges and Indus, but for low-lying areas such as the Gangetic Plain, at much lower percentages than thought several years ago. The effect of glacial retreat will be most evident during the dry season, particularly in the west. In all seasons, changes in many regions are likely to be dominated by shifts in the location, intensity, and variability of precipitation (both rain and snow) rather than glacial retreat. Glacial meltwater is not a major contributor for river systems to the east but is more important for river systems to the west. Kaltenborn et al. (2010) conclude that,

In general, the impact of melting glaciers on the seasonal distribution of river flow is greatest where (i) ice melt occurs during a dry season; (ii) glacier meltwater flows into semi-arid areas; and/or (iii) small annual temperature cycles mean that there is little seasonal variation in snow cover. Conversely, the seasonal effect is smaller where there is significant precipitation during the melt season, such as the monsoonal central and eastern Himalaya.

Melting of glacial ice plays an important role in maintaining water security during times of drought or similar climate extremes. For example, in the European Alps during the drought year of 2003, glacial melt contributions to August discharge of the Danube River were about three times greater than the 100-year average (Huss, 2011). Thus, water stored as glacial ice is the region’s hydrological “insurance,” acting as a buffer against the hydrological impacts brought about by a changing climate, releasing the stored water to streams and rivers when it is most needed.

There may be normal, even increased, amounts of available meltwater to satisfy dry season needs because of the release of “insurance” water from storage in retreating glaciers for the next several decades (Barnett et al., 2005). To illustrate, the role of glacial wastage contributions to discharge under future warming scenarios was investigated for three highly glacierized catchments in the Alps that have long-term climate and discharge records (Huss et al., 2008). Annual runoff from the drainage basins shows an initial increase which is due to the release of water from glacial storage. After some decades, depending on catchment characteristics and the applied climate change scenario, runoff stabilizes and then drops below the current level. Retreating glaciers of the HKH in the short



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5 Conclusion T he climate and hydrology of the HKH region melt occurs during a dry season; (ii) glacier meltwater are changing. There are many important uncer- flows into semi-arid areas; and/or (iii) small annual tainties about the current state of physical and temperature cycles mean that there is little seasonal variation in snow cover. Conversely, the seasonal ef- social systems in the region in addition to the uncer- fect is smaller where there is significant precipitation tainties about the future. However, not everything is during the melt season, such as the monsoonal central uncertain or unknown. It is important to consider the and eastern Himalaya. impact of glacial retreat on regional water resources Melting of glacial ice plays an important role in in the larger, hydroclimatic and social context of the maintaining water security during times of drought or HKH region. The effects of climate changes on glacier similar climate extremes. For example, in the European dynamics will affect both the supply and demand for Alps during the drought year of 2003, glacial melt water in the Himalayan region, and these changes will, contributions to August discharge of the Danube River in turn, affect the vulnerability of key populations to were about three times greater than the 100-year aver- freshwater problems. Glacial retreat is only one factor age (Huss, 2011). Thus, water stored as glacial ice is that contributes to changes in the hydrological cycle, the region's hydrological "insurance," acting as a buffer and the relative importance of glacial meltwater var- against the hydrological impacts brought about by a ies across the region and between seasons. In most changing climate, releasing the stored water to streams instances, the contribution to surface-water discharge and rivers when it is most needed. of snowmelt exceeds that of glacial melt. Glacial melt There may be normal, even increased, amounts of does contribute to the water flow in major rivers such available meltwater to satisfy dry season needs because as the Ganges and Indus, but for low-lying areas such of the release of "insurance" water from storage in as the Gangetic Plain, at much lower percentages than retreating glaciers for the next several decades (Barnett thought several years ago. The effect of glacial retreat et al., 2005). To illustrate, the role of glacial wast- will be most evident during the dry season, particularly age contributions to discharge under future warming in the west. In all seasons, changes in many regions are scenarios was investigated for three highly glacierized likely to be dominated by shifts in the location, intensity, catchments in the Alps that have long-term climate and variability of precipitation (both rain and snow) and discharge records (Huss et al., 2008). Annual run- rather than glacial retreat. Glacial meltwater is not a off from the drainage basins shows an initial increase major contributor for river systems to the east but is which is due to the release of water from glacial stor- more important for river systems to the west. Kalten- age. After some decades, depending on catchment born et al. (2010) conclude that, characteristics and the applied climate change scenario, In general, the impact of melting glaciers on the sea- runoff stabilizes and then drops below the current sonal distribution of river flow is greatest where (i) ice level. Retreating glaciers of the HKH in the short 93

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94 HIMALAYAN GLACIERS: CLIMATE CHANGE, WATER RESOURCES, AND WATER SECURITY term (decadal time frame) will subsidize surface flows Although economic development could reduce adverse by melting water held in storage, mitigating immedi- outcomes, including loss of life, monetary loss could ate losses to discharge by retreating glaciers (Kaser et increase. al., 2010). As noted in Chapter 2, paleoclimate records sug- A WAY FORWARD gest a mixed record of wetness and dryness during the 20th century in the monsoon-dominated eastern HKH When considering the link between humans and and hydrological modeling indicates that glacial melt is the environment in the context of water security in the not a major contributor to river systems in the east (i.e., HKH region, four themes emerge: (1) there is signifi- the Ganges, Yangtze, and Yellow). Thus, for the east- cant variability in the climate, hydrology, and glacier ern HKH, these factors could result in little change to behavior as well as the demographics and water-use annual surface-water discharge, but could result in the patterns of the region; (2) uncertainties exist and will loss of "insurance" water that glacial melt provides for continue to exist in both the physical and social systems; water security during times of drought. In the western (3) to reduce and respond to this uncertainty there is a HKH, paleoclimate records indicate a trend toward need for improved monitoring of both the physical and wetter conditions in the 20th century and hydro- social systems; and (4) in the face of uncertainty, the logical models indicate that glacial melt is much more most compelling need is to improve water management important in the west (i.e., the Indus Basin). Thus, the and hazards mitigation systems. consequences of climate change to water security could Theme 1: There is significant variability in the climate, be large if a reduction in available surface water either hydrology, and glacier behavior in the region as well as the annually and/or seasonally occurs in the western HKH. demographics and water-use patterns within the region. However, the trend toward wetter conditions in the The retreat rates of Himalayan glaciers vary over time western HKH confounds this assessment. and space, with the rate of retreat being higher in the During situations such as these, groundwater, a east than the west. There are confounding factors such significant amount of which is supplied to the major as dust and black carbon that will affect glacial melt river plains of the region by the Himalayas, will be and in some cases increase glacial wastage. Changes looked to as a source to offset water scarcity. Thus, in the monsoon will probably be more important than water security issues for lowland populations over the changes in glacial wastage at lower, downstream eleva- next decade are more likely to come from overdrafting tions. Rates of urbanization vary across the region, of groundwater resources than changes in discharge as does the portion of the population with access to from retreating glaciers. improved water and sanitation. Although a greater understanding of the glaciers Theme 2: Uncertainties exist and will continue to of the HKH region will inform knowledge about exist in both the physical and social systems. The impact water security in the region, improved understanding of future climate change is uncertain but will probably of the science of the glaciers is itself not sufficient to accelerate rates of glacial retreat. Accelerated glacial answer all questions about the relationship between retreat rates will have significant impacts in local, high- the hydrology, the population, and the policies and mountain areas but will probably not be very important politics of the region. As discussed in Chapter 3, social downstream. As the region's population becomes more changes are affecting water use at a greater rate than urbanized and standards of living change, water-use environmental factors are affecting the availability of patterns will also change in ways that will be difficult water. For example, rising standards of living, includ- to predict. Existing demographic methods to not allow ing improving and changing diets and greater energy for projections at sufficient spatial resolution to deter- use, will have a significant effect on water-use patterns mine whether, for example, certain basins and elevation over the coming decades. Even if streamflow remains zones will experience higher rates of population growth relatively stable in the short term, human factors could than others and how the demographic composition of lead to water scarcity. Changing standards of living those specific areas will change. In both the physical could also influence vulnerability to natural hazards. and social systems, stationarity--the assumption that

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CONCLUSION 95 the systems will fluctuate within a known range of priority. These needs are critical to more fully address variability--will no longer apply. In other words, the the questions in the Committee's charge. past is not a good basis for prediction, and past trends in the climate, hydrology, glaciers, and population of Physical Geography the region will not be a viable guide for the future (e.g., Milly et al., 2008). The HKH is one of the least-observed regions on Theme 3: To reduce and respond to this uncertainty, Earth. Currently available data lack the necessary spa- there is a need for improved monitoring of both the physi- tial and temporal resolution, as well as quality, to fully cal and social systems. Monitoring will need to occur understand the region. There is a need for carefully on a more extensive and consistent basis. Without designed surface observing systems (including tempera- enhanced monitoring, the information needed to ture, precipitation amount and type, streamflow, glacial respond to changing environmental and social condi- mass balance, glacier albedo, groundwater, paleoclimate tions will be unavailable. Monitoring and research proxies) that are integrated with satellite observations will further understanding of both the physical and to provide comprehensive monitoring of the region. human systems in the region, and identify the various In addition to new data, pooling of existing data and options available to respond to change in the face of resources, including release of relevant classified or uncertainty. restricted satellite imagery or water data, and sustained Theme 4: In the face of uncertainty, the most compel- international cooperation and data sharing are critically ling need is to improve water management and hazards important to advance understanding and reduce uncer- mitigation systems. Existing patterns of water use and tainties. Comprehensive monitoring and data sharing water management need improvement. As discussed in would help answer the following questions: Chapter 3, some progress has been made in improved assessments in the recent past. Going forward, improved Climate, meteorology, and aerosols: What are the implementation of lessons from these assessments in effects of greenhouse gas warming and black carbon water policies and programs will be necessary. Options radiative forcing on winds, temperature, precipitation for adapting to climate change are discussed in greater variability, and trends in the summer monsoon and detail in the next section. However, the people most mid-latitude westerlies? How much of the regional likely to be affected by changing water security in South atmospheric aerosol loading is driven by local emissions Asia are the rural and urban poor who have the least compared with transport from remote sources? How do capacity to adapt to changing environmental and social black carbon deposition, snowfall, and snow turnover conditions and hazards. Management of groundwater processes combine to affect the albedo of glaciers and and demand-side management are among the areas snowpack? How has the temperature in the mid and where improvements can be made. lower troposphere changed? How do current changes in the regional climate compare to natural climate changes RESEARCH AND DATA NEEDS that occurred in the past? How will the monsoon change in the future? Anticipating future conditions in the HKH region Glaciers: What is the relationship between cli- is hindered by an incomplete understanding of current mate changes and the mass balance of the HKH gla- conditions and of both the extent to which natural ciers? What is the response time of individual glaciers feedback mechanisms will generate new equilibria to climate forcing, and how does this response time and human systems will adapt to signals of stress and vary among glaciers in the region? Have temperature change. As discussed throughout the report, many open changes in the mid and lower troposphere affected the scientific questions remain about the physical and social equilibrium line altitude or the ratio of snow to rain? systems of the region, which, if addressed, could lead to How does snow cover change seasonally? a greater understanding. These research and data needs Hydrology: What is the relative contribution, are presented in roughly the same order as the topics seasonally and annually, of glacial wastage and melt- appeared in the report, and the order does not indicate water to total streamflow in the major rivers of the

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96 HIMALAYAN GLACIERS: CLIMATE CHANGE, WATER RESOURCES, AND WATER SECURITY HKH region? What are the surface water-groundwater of floods, droughts, heat waves, and secondary impacts recharge mechanisms in the region? How will climate associated with climate variability. Although deaths change affect groundwater supply? How can hydrologi- and numbers of persons affected are regularly reported, cal data become more widely accessible to the science and to a lesser extent physical damages (e.g., houses and and management communities? How can remote sens- infrastructure destroyed), rigorous economic damage ing be used in conjunction with well data to increase and need estimation are a priority for policy research. understanding of groundwater in the region? Disaster resilience, recovery, and reconstruction pro- cesses are less well documented than initial impacts, Human Geography in part because they occur when postdisaster attention wanes. The human dimensions of loss and reconstruc- Currently available demographic compositional tion require intensive field research, and strong rela- data do not conform to geophysical parameters and lack tionships between research and practice. New methods the necessary spatial resolution to determine whether, of postdisaster mobile phone survey data transfer and for example, certain basins and/or elevation zones will mapping have considerable promise for advancing experience higher rates of population growth than socioeconomic lines of research on a regional scale. others. Current understanding of water usage is poor Improved economic, social, and political datasets would because of a lack of regional datasets. Remote sens- help answer the following questions: ing advances may address some of these deficiencies, particularly in the plains. Improved measurement of Natural hazards and vulnerability: Which popu- water withdrawals from surface water, and even more lations in the region will be most vulnerable to a so groundwater pumping, will be crucial for develop- changing climate? What are the proximate and root ing, monitoring, and managing regional water budgets, causes of vulnerability in the HKH region? How do hazards, and stresses. As lowland water and energy alternatives for secure and sustainable livelihoods dif- scarcity may increase demand for mountain water stor- fer for populations in the mountains more dependent age, advances in water use analysis will have increasing on glaciers and larger downstream populations on the importance. Improved datasets and monitoring would plains? How can the results of collaborative research help answer the following questions: on exemplars of disaster-resilient settlement, infra- structure, and housing in mountain environments of Demographics: How will populations change in the HKH region complement initiatives to increase areas with water scarcity as compared with areas with collaboration on climate change, glaciology, glacial lake sufficient water supplies? outburst flood monitoring, and flood warning--and Water-use patterns: How can major improve- help increase the prospects for successful adaptation to ments in water-use data collection, access, and utiliza- changes in climate and hydrology in the region? How tion be accelerated? How do changing lifestyles, stan- can early-warning systems be used to minimize deaths dards of living, and demographic trends affect water from hazards such as GLOFs? supply, demand, and management? Security dynamics and water conflict: What is Water management: What dams are planned in the current and future institutional capacity to absorb the region, and how will they affect water manage- change at the local, national, and international levels? ment and hydrology? How can the results of inter- How can the research community design appropri- national- and national-level climate assessments be ate metrics to monitor the capacity of governmental incorporated into water management and policy at the institutions to address water stress? Does water stress, subnational level? among other stressors, affect state stability? Through what mechanisms? What are the possibilities for better Environmental Risk and Security incorporation of scientific information about glaciers, hydrology, and climate change into international Hazard datasets remain inconsistent and not coded water-sharing treaties? Will climate change impacts in ways that enable causal analysis of large-N samples on glacial melt and hydrology be severe enough to

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CONCLUSION 97 constitute a threat to water and food security and/or (i.e., they would be good strategies to take regardless political stability? of how severe climate change's impacts become). In general, many strategies that encourage good manage- OPTIONS FOR ADAPTING TO ment of water resources under current climate could CHANGES IN CLIMATE, HYDROLOGY, serve as useful adaptation strategies in a world with AND WATER AVAILABILITY altered climate. Similarly, because people with fewer resources are often more vulnerable to climate change There are some potential adaptations that govern- disruptions, many strategies that promote sustainable ments, communities, or individuals may consider in economic development could also be useful adaptation response to climate change's effects on the hydrologic strategies in the face of climate change. system. Even with significant international progress There is a large literature on the topic of adapta- toward mitigating greenhouse gas emissions, with tion, and the Committee can only briefly describe current levels of carbon dioxide and other greenhouse a few potential adaptation options in this section. gases in the atmosphere, there will be significant cli- Adaptation was discussed previously in the context of mate change over the next few decades, and thus some water management institutions and disaster agencies in adaptation, particularly to strengthen water manage- Chapters 3 and 4, respectively. Here, the Committee ment systems, will be necessary. describes options that affect the supply or timing of It can be difficult to make decisions about which water available to users, followed by options that affect adaptation strategies to pursue in the face of uncertainty the demand of water by users. Then the Committee about the magnitude of climate change's hydrological discusses integrated watershed management and river impacts. Also, there are significant uncertainties about basin management, which often consider both supply the effectiveness of various adaptation options. Some and demand. Finally, the Committee discusses adap- adaptation options have been shown to be effective in tation options to decrease the risk of negative impacts adapting to variability under current climatic condi- from flooding. tions, but it is not known whether they will hold up under a changing climate (NRC, 2010a). Additionally, Adapting Under Uncertainty: The Need to Monitor implementation of adaptation strategies can be chal- lenging in developed countries: As discussed above, and throughout this report, Numerous attempts have been made to develop and lack of understanding and a paucity of data about implement adaptive management strategies in envi- current and emerging conditions of glacial melt and ronmental management, but many of them have not the hydrological system more generally are major been successful, for a variety of reasons, including sources of uncertainty in the region. Adaptive man- lack of resources, unwillingness of decision makers to agement1 of water resources depends critically on admit to and embrace uncertainty; institutional, legal, observations of changes that are occurring. Therefore, and political preferences for known and predictable outcomes; the inherent uncertainty and variability adaptation options will rely on expanding the moni- of natural systems; the high cost of implementation; toring programs in the region, including increased and the lack of clear mechanisms for incorporating hydrometeorological data; measurements of glacial scientific findings into decision making. Despite all of mass balances, seasonal snow cover, black carbon on the above challenges, often there is no better option snow and ice; assessment of GLOF risks; streamflow for implementing management regimes. . . . (NRC, data (i.e., discharge); water quality; and demographic 2011b) patterns of water use. Both remotely sensed and in And developing countries are likely to face as many situ data are valuable for such monitoring programs challenges. (USAID, 2010). Good first adaptation strategies to pursue are gen- 1 Adaptive management is a flexible approach designed to meet erally flexible (i.e., they do not lock a country or other management goals under a variety of future climate conditions entity into a long-term commitment to the strategy), and requires a nonstationary view (e.g., Milly et al., 2008; NRC, are relatively low-cost and are "no regret" strategies 2010a, 2012b).

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98 HIMALAYAN GLACIERS: CLIMATE CHANGE, WATER RESOURCES, AND WATER SECURITY In addition to uncertainties in the physical sys- New dams, either at a large or a small scale, are one tems of the region, there are also uncertainties in the way to increase hydropower and/or storage in both the social systems. Adaptive management of the region's Indus and the Ganges/Brahmaputra, although any new water resources will require a greater understanding dam construction would likely be a politically contro- of how each option will affect downstream users, the versial decision, both within a country and between potential negative consequences of each option, and countries. Because climate will be changing over the whether an option may prove to be maladaptive. In long term, dam planning needs to include multiple addition, it will be necessary to monitor the impacts scenarios over the projected life of the dam to ensure of adaptation policies, and make adjustments to the its usefulness under climate change. As well as the policy as required. Interventions that can be repurposed potential for being maladaptive over time, dam con- and customized are especially desirable when operat- struction could also have unintended and cumulative ing under conditions of uncertainty and change. The negative consequences on the regional ecology, settle- capability to support and integrate interventions into ments, and downstream sediment supply (e.g., NRC, local innovations that are effective is also of great value. 2011a). Additionally, geological instability limits the Effective program evaluation, something that is often stability of major dams and reservoir development in overlooked, is especially important when designing the region and adds risk from dam failure. In any event, and implementing interventions under conditions of dam management regimes at existing dams will need to uncertainty. A central concern with adaptation strate- be altered, so that, rather than being operated on the gies is their potential for changing power relationships basis of historical distribution of streamflow events, and introducing conflict, and for creating unrealistic dam operation is based on the current (altered) climate. expectations that can become difficult to manage and Because changes in dam management will affect the a source of significant social tension. Some manage- availability of water to downstream users, either in ment and adaption options in the face of hydrological the same country as the dam or a different one, such change may themselves detrimentally affect water changes may have the potential for conflict if decisions availability for downstream riparians, possibly sparking are not made cooperatively with all affected parties. or exacerbating water conflicts or political tensions. More local-scale catchment systems can store water In other words, the rational pursuit of otherwise rea- in wet seasons for use in dry seasons. Catchments are sonable adaptation options (e.g., the construction of often constructed and managed at the local level. They more water storage or the expansion of irrigation) as are relatively less expensive, lower impact, and easier to insurance against prospective climate-induced short- change than large dams. falls or volatility in future supply could have negative Another adaptation option sometimes used in the consequences. face of water shortages is to construct a system for interbasin water transfers, moving water from a rela- Supply-Side Strategies tively wet place to a relatively dry place. Such systems are often extremely expensive to construct, such as the One potential impact of climate change on the Chinese plan to divert water from south China to the region's hydrology is to increase the frequency of both north, the South-North Water Diversion Project, which high-flow events and low-flow events. One adaptation is estimated to cost around $62 billion dollars (Wong, option is to try to increase storage, so that water can be 2001). Moreover, any plan by upstream countries for stored during wet periods for use during dry periods. an interbasin transfer in the Ganges/Brahmaputra Three approaches to this effort are improved water sup- Basin would likely have international political repercus- ply forecasting, dams, and catchment systems. In each sions and could be the basis for a conflict. Interbasin approach, the need for flexible systems that can adapt water transfer is further complicated by the lack of in a range of uncertain futures suggests that small- understanding of the impact of climate changes on the scale and low-cost systems may be the best options for hydrology of the region. Changes in the flow of rivers at least the planning horizon of most countries and in the relatively wet areas could impair their ability to donors. adequately provide water for the dry areas, decreas-

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CONCLUSION 99 ing the effectiveness of a very expensive project. For (Box 3.1) may serve as a climate change adaptation, these reasons, proposals for interbasin water transfers but success depends on the level of community cohe- are generally controversial among hydrologists, policy sion and will be limited unless enough groundwater is analysts, NGOs, and the courts. available for the system. Because available data indicate Usually, climate change adaptation is considered a the groundwater is currently being used unsustainably separate topic from climate change mitigation (i.e., the in the region, this adaptation option, by itself, is likely reduction in emissions of pollutants that cause climate not realistic; however major advances in conjunctive change). Greenhouse gas emission mitigation is by management of surface and groundwater will be a high necessity a global challenge, because most greenhouse priority. gases are well mixed in the atmosphere. However, for There are also options for local water storage. For South Asian countries the control on the emission of instance, some high-altitude communities in the HKH aerosols and particulate matter could help mitigate region have experimented with building small ponds the regional pattern of climate change, because these that freeze in the winter into miniglaciers (ICIMOD, pollutants play an important regional role in, respec- 2000b). These miniglaciers then melt slowly over the tively, the monsoon cycle and the rate of snowmelt growing season, providing farmers and towns with and icemelt. Although the exact scientific relationship water. Larger reservoirs could potentially become a between these pollutants and regional climate is still an hazard due to earthquake-induced failure, or change area of active scientific exploration, there is potential the energy balance of snow-covered basins. Addition- that countries could cooperate to maintain traditional ally, there are emerging technologies that harvest water climate patterns to some extent by limiting emissions of from humid air (ICIMOD, 2000a). An increasing aerosol and particular matter. Because actions by a small number of cities in South Asia are adopting harvest- set of countries could significantly change the regional ing requirements in building and development codes concentration of these pollutants, such an agreement (Agarwal et al., 2001). Another way to increase water could avoid the problem facing many global agreements supply at the local level is to reuse treated wastewater about greenhouse gas pollutants, where there are many (e.g., Kumar et al., 2005), particularly for irrigation. actors who have to approve an agreement. Reducing Given the uncertainty in the future magnitude of aerosol emissions is also a resilience-building strategy, climate change impacts, one general adaptation option in that it has the co-benefit of reducing respiratory dis- is to expand the diversity of techniques that are used eases and premature deaths, especially among women to obtain water. The idea is that instead of just one and children (NRC, 2010b). source, which could be critically affected by climate One common adaptation strategy used to address change, multiple sources would be relatively less sensi- short-term water shortages is to withdraw ground tive to disruption by climate change, unless climate water. Groundwater is a form of water storage, and can change were to impact all the sources simultaneously be sustainably used as long as withdrawal rates do not and synchronously. exceed recharge rates of the aquifer. However, changes in the regional hydrology could affect the recharge Demand-Side Strategies rate, leading to uncertainties in the amount of water that can be sustainably withdrawn. Increased use of Any strategy that increases water-use efficiency can groundwater may be one adaptation to climate change, serve as a potential climate change adaptation, but can but some major aquifers are already being depleted by also increase a population's vulnerability if users do not excess withdrawals, so there are (often uncertain) limits see the value in using less water. Because users some- to how extensively increasing withdrawal from ground- times expand their use to take advantage of increased water can be a long-term adaptation to climate change. water availability, efficiency gains do not always trans- In addition, groundwater withdrawal in delta regions late into reductions in total water use. These gains may could lead to increased subsidence, which in turn leads still increase the productivity of a given water use per to increased sea level rise. Increased use of the tradi- unit of water withdrawn and hence a sector's resiliency tional karez or qanat system of channeling groundwater to climate change. The agricultural sector is the biggest

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100 HIMALAYAN GLACIERS: CLIMATE CHANGE, WATER RESOURCES, AND WATER SECURITY user of water, and the one with the greatest potential for ments to account for further changes in precipitation increases in water-use efficiency to serve as an adapta- patterns. The focus of adaptation strategies might also tion. For instance, cotton, rice, and sugarcane irrigation be how to reduce irrigation demands during extreme in the Indus Basin use a large volume of water, and low-flow periods of the year. Although forgoing irriga- small reductions in the amount of water used per hect- tion during low-flow events imposes an economic cost are could significantly reduce water use by these crops. on farmers, it may leave enough water in surface water Another sector where gains in water-use efficiency and groundwater for downstream users. However, this may be helpful in adapting to climate change would may have a negative impact on regional food security, be the energy sector. Thermoelectric power plants that again demonstrating the complexities of adaptation use once-through cooling systems withdraw signifi- options. cantly more water than recirculating cooling systems. Although most of this water is discharged to the stream River Basin Management after use, there can be local thermal impacts. A switch from once-through cooling to recirculating cooling can The ideal model for river basin management significantly reduce water withdrawals by the sector. and the processes its development, management, and However, recirculating systems have higher consump- maintenance have been given considerable thought and tive use than once-through systems, so trade-offs are have evolved through time (Molle et al., 2010; NRC, necessary (NREL, 2003). Municipal water systems also 2010c). Embedded within this discussion is the concept could improve technological efficiency, perhaps as part of environmental flow (EF) that describes the water of extending their coverage to growing populations. regime (quantity, timing, and quality) within a system Such adaptation strategies require large infrastructure that is required to maintain the surrounding ecosystem investments, which affect their feasibility. and human livelihood. Most EF assessments have been There are a number of tools available to affect developed and performed in developed countries. Yet demand management. Some of these are technology assessment of EFs in developing countries, such as based and include flow restrictors, low-flush toilets, those in the HKH region, is a necessary step toward closed conduit irrigation systems--sprinkler and drip successful river basin management, and some progress systems--and water metering, either by itself or in has been made (Smakhtin et al., 2006). connection with rational regimes of water pricing. In Often, water managers implement minimum general, the relatively high capital costs of these tech- EF requirements based on system objectives such as nologies make their adoption prohibitively expensive maintaining populations of fish at a given level or for much of the water-using population in the region. supplying local communities and/or agriculture with More decentralized demand management techniques a given volume of water (NRC, 2010d). When a river include water pricing and water rationing. Shah (2009) basin is at the point where there is no more utilizable describes how the availability of complementary inputs flow in a given year, the basin is said to be "closed" such as energy for pumping groundwater have been (Falkenmark and Molden, 2008). If a basin is closed used successfully to manage demand for irrigation and utilization continues, an unsustainable situation water in some areas. This is accomplished by making ensues. The waters of the Indus and the Ganges are energy available only during certain periods of the day. already said to be overallocated or nearing overalloca- These decentralized demand management techniques tion, thus "closed" basins (Falkenmark and Molden, have the advantage of allowing each user to adjust con- 2008; Smakhtin, 2008). sumption according to their circumstances. Efforts to effectively manage river basins attempt to More significant climate change impacts on hydrol- avoid this type of situation and the associated impacts ogy might necessitate changes in land use over time. such as a decrease in water quality or inequitable shar- For instance, farmers might adapt to climate change ing of the resource. It is increasingly being realized that by shifting from a water-intensive crop that requires the biological and social systems supported by water significant irrigation to a less intensive, perhaps rainfed, are not adequately described by a single minimum flow crop. Such a strategy would require periodic adjust- requirement or a set of flow requirements, but a more

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CONCLUSION 101 comprehensive assessment of water management is for water management and health (clean water and needed that accounts for hydrological change (NRC, sanitation) (USAID, 2010). 2012b). This would include, for example, basic strate- gies such as demand management, increased storage, Managing Flood Risks establishment of EFs, and operational flexibility (NRC, 2012b). The first step in reducing potential flooding One option, integrated watershed management impacts from climate change is to map which com- (IWM), attempts to consider both demand- and munities are at risk (NRC, 2009). The primary risk supply-side strategies for managing water in a basin of flooding from glacial melt per se is GLOFs, which to find a solution to any water problems in the basin. are mostly a risk to high-elevation communities Although definitions of IWM vary, the general focus along rivers and streams, but similar phenomena can of management is on looking at all uses of water pose risks at lower elevations when debris or ice jams simultaneously when making policy decisions. For the dam water that then bursts out. In contrast, the risk Ganges/Brahmaputra and the Indus, there is a clear of downstream flooding may be increased by climate need, for example, to link management of surface-water change, depending on a number of factors including resources more closely with management of ground- the rate and timing of snowmelt and the magnitude water resources. There is also a need for management of monsoonal rains. Because there are many large decisions to be made that consider the needs of water settlements near rivers in the lower floodplains of the users in different countries. This is often a difficult task Ganges/Brahmaputra and Indus basins, if climate politically, but the existing international agreements change increases the risk of downstream flooding (e.g., Indus Water Treaty) illustrate that agreements events, it could significantly affect hundreds of mil- about water allocations can be achieved. lions of people. Many of the international agreements in the region Once communities at risk from flooding are iden- are not yet fully integrating climate change consider- tified, there are various options that can be used to ations into their decision making, and any progress on minimize risk, although many are very difficult to this front could serve as a climate change adaptation, implement. New development can be limited in flood- by ensuring that basin water resources are managed plains or other sensitive areas, or existing homes and efficiently and equitably in a changing climate. Climate infrastructure in floodplains at risk of flooding can be change planning at the national level is important. Even decommissioned. Vegetation, including forests, can be if many national hydrological agencies are considering restored where needed to retain water and thus miti- the potential impacts of climate change, many other gate flooding. Governments can offer flood insurance national government agencies are not. If, for instance, programs, as the Federal Emergency Management agencies deciding on the construction of new irrigation Agency's National Flood Insurance Program does in systems are not adequately considering the effect of the United States, both mandatory in high-risk areas climate change in their decisions, then countries may and nonmandatory in low-risk areas. Alternatively, commit significant resources to irrigation that will not new infrastructure can be built to protect areas at risk be useful in a future climate. of floods (e.g., dams, pumping stations, or storage At national and subnational levels, opportunities basins). Sometimes this infrastructure is traditional exist to provide knowledge and assistance to farmers "gray" infrastructure, such as levees. However, levees in efficient water use, especially as regards irrigation are often considered to be maladaptive, because they systems. Local or subnational organizations, networked can encourage settlement in vulnerable low-elevation for greater impact, can develop farm-level and coopera- areas (NRC, 2012b). In other cases, so called "green" tive strategies for both groundwater and surface-water infrastructure solutions are used, where floodplains are use. Another adaptation option includes establishing reconnected hydrologically with rivers to allow flood or strengthening community-based water user associa- waters to spread out over the entire floodplain. This tions (WUAs) and forest user groups (FUGs), with reduces the flooding risk to downstream communities better coordination links to national policy frameworks by reducing the height of peak flows in a river.

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102 HIMALAYAN GLACIERS: CLIMATE CHANGE, WATER RESOURCES, AND WATER SECURITY Flood management also includes early warning mate change are already more extensive than previously systems, which can reduce deaths and injuries, and thought or recognized, and are mounting more quickly disaster response capacity, which is highly variable and more extensively than predicted. This suggests that in the region. Improvements in each of these areas in discussions of climate change impacts over 50-year- would be adaptive to both glacial melt and hydrologi- plus time horizons may have to be replaced with cal change. ten-year-plus time horizons, and more comprehensive There is a growing sentiment within parts of the approaches to hydroclimatic forecasting, natural haz- climate science community that the social effects of cli- ards mitigation, and water management.