Table 4-13 summarizes some supply- and demand-side adaptive options, by water-use sector. Each option has a set of economic, environmental, and political advantages and disadvantages.

Table 4-13: Supply-side and demand-side adaptive options: some examples.
Supply-Side			Demand-Side
Option	Comments		Option	Comments
Municipal water supply
– Increase reservoir capacity – Extract more from rivers or groundwater – Alter system operating rules – Inter-basin transfer – Desalination – Seasonal forecasting	Expensive; potential environmantal impact – Potential environmental impact – Possibly limited opportunity – Expensive; potential environmental impact – Expensive (high energy use) – Increasingly feasible		– Incentives to use less (e.g., through pricing) – Legally enforceable water use standards (e.g., for appliances) – Increase use of grey water – Reduce leakage – Development of non-water-based sanitation systems	Possibly limited opportunity; needs institutional framework – Potential political impact; usually cost-inefficient – Potentially expensive – Potentially expensive to reduce to very low levels, especially in old systems – Possibly too technically advanced for wide application
Irrigation
– Increase irrigation source capacity	– Expensive; potential environmental impact		– Increase irrigation-use efficiency – Increase drought-toleration – Change crop patterns	– By technology or through increasing prices – Genetic engineering is controversial – Move to crops that need less or no irrigation
Industrial and power station cooling
– Increase source capacity – Use of low-grade water	– Expensive – Increasingly used		– Increase water-use efficiency and water recycling	– Possibly expensive to upgrade
Hydropower generation
– Increase reservoir capacity	– Expensive; potential environmental impact – May not be feasible		– Increase efficiency of turbines; encourage energy efficiency	– Possibly expensive to upgrade
Navigation
– Build weirs and locks	– Expensive; potential environmental impact – Potential environmental impact		– Alter ship size and frequency	– Smaller ships (more trips, thus increased costs and emissions)
Pollution control
– Enhance treatment works	– Potentially expensive		– Reduce volume of effluents to treat (e.g., by charging discharges) – Catchment management to reduce polluting runoff	– Requires management of diffuse sources of pollution
Flood management
– Increase flood protection (levees, reservoirs) – Catchment source control to reduce peak discharges	– Expensive; potential environmental impact – Most effective for small floods		– Improve flood warning and dissemination – Curb floodplain development	– Technical limitations in flash-flood areas, and unknown effectiveness – Potential major political problems

Most of these strategies are being adopted or considered in many countries in the face of increasing demands for water resources or protection against risk. In the UK, for example, water supply companies currently are pursuing the “twin track” of demand management and supply management in response to potential increases in demand for water (although there is a conflict between different parts of the water management system over the relative speeds with which the two tracks should be followed). These management strategies also are potentially feasible in the face of climate change. Nowhere, however, are water management actions being taken explicitly and solely to cope with climate change, although in an increasing number of countries climate change is being considered in assessing future resource management. In the UK, for example, climate change is one of the factors that must be considered by water supply companies in assessing their future resource requirements—although companies are highly unlikely to have new resources justified at present on climate change alone.

The continuing debate in water management (Easter et al., 1998) is between the practicalities and costs of supply-side versus demand-side options, and this debate is being pursued indepedently of climate change. The tide is moving toward the use of demand-side options because they are regarded as being more environmentally sustainable, cost-effective, and flexible (Frederick, 1986; World Bank, 1993; Young et al., 1994; Anderson and Hill, 1997). “Smart” combinations of supply-side and demand-side approaches are needed, although in many cases new supply-side infrastructure may be necessary. This is particularly the case in developing countries, where the challenge often is not to curb demand but to meet minimum human health-driven standards.

There do appear, however, to be numerous “no regret” policies that warrant immediate attention. In this context, a “no regret” policy is one that would generate net social benefits regardless of whether there was climate change. Examples include elimination of subsidies to agriculture and floodplain occupancy and explicit recognition of environmental values in project design and evaluation. The effect of successful demand-side policies is to reduce the need for supply augmentation, although they may not prevent such needs entirely if changes are large. Such policy changes represent the minimum package of “anticipatory policy changes” in response to climate change.

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