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