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