the world of 10 billion, water experts project, the demand for water could be 50 percent higher than it is now. Where will it all come from? New supplies will not be easy to find. Few lakes and rivers are unexploited, and aquifers are being depleted. Equally difficult would be stretching existing water supplies by reducing waste and encouraging thrifty use. Adding to the pressure, climate change is shrinking glaciers and drying streams.