seen environmental consequences of existing water projects require attention. And in the international arena, water (both its quantity and quality) may become far more important than oil in the next century as a source of conflict and, potentially, war.
Water must also be managed in a climatic as well as a social context. Water resources decisions are made under the assumption that the climate of the recent past is representative of the future. The possibility of global change suggests that this assumption may be invalid and adds uncertainty to the water management agenda. While climate change may impact water resources significantly, it is interesting that a major source of uncertainty in climate change also involves water. Water is important in the energy balance of the earth: as an agent for energy transport and as a factor in the optical properties of clouds and the atmosphere. A major goal of the World Climate Research Program (a joint program of the World Meteorological Organization and the International Council of Scientific Unions) is to improve understanding of the climate system through a Global Energy and Water Cycle Experiment (GEWEX). Much of the work that must be done by GEWEX to improve our understanding of the hydrologic cycle of the earth is also needed to improve water resources management. Conversely, much of the work needed to improve water resources management should help (in part through GEWEX) reduce uncertainty about climate change and the effects of climate change on water resources. This is a very important issue that will be developed below.
Water management has two parts: one long range, involving the planning, design, and construction of new facilities; the other short range, involving the operation of existing facilities. Both long-range and short-range decisions are sensitive to the hydrological effects of climate variability and change. Water management decisions depend on water resources forecasts, and these forecasts must take into account the effects of climate variability and change.
The drought of 1988 focused national attention on the role of water resources in our country. Print and electronic media brought clear images of the consequences of drought: barges stranded on sandbars in the Mississippi River, empty reservoirs, and withered corn fields. The drought dramatically illustrated that industries tied to the availability of water are inherently risky. Risky decisions in water-based industries are a daily fact of life: barge companies decide how heavily loaded each barge should be; electric and water utilities decide how much effluent can be safely dis-