Global climate change will certainly produce a mixture of both beneficial and harmful impacts. Beneficial impacts might include reduced winter heating demands and longer growing seasons in some areas, while harmful impacts will include the health and energy demand impacts of more frequent summer heat waves, and increased stress on natural ecosystems and poor countries that lack resilience to change. Here, we are particularly interested in the possible impacts of climate change on the water utility industry. As will be described below, large changes are possible in total available water supplies, in the seasonal distribution of surface flows, in water quality and in the frequency and severity of flood and drought events. However, the details of how these changes will unfold at any given location are likely to remain highly uncertain.

Water demands, particularly for irrigation, are likely to change as well. Effective adaptation to such changes may require careful evaluation of the implications of a wide range of possible future climate scenarios.