1. Introduction
Population growth and higher living standards will cause ever increasing demands for good quality municipal and industrial water, and ever increasing sewage flows. At the same time, more and more irrigation water will be needed to meet increasing demands for food for growing populations. This will require intensive management and international cooperation. Since almost all liquid fresh water on the planet occurs underground, groundwater will be used more and more and, hence, must be protected against depletion and contamination, especially from non-point sources like intensive agriculture.
Such a holistic approach requires not only supply management, but also demand management, water quality management, recycling and reuse of water, economics, conflict resolution, public involvement, public health, environmental and ecological aspects, socio-cultural aspects, water conjunctive use of surface water and groundwater, water pollution control, flexibility, regional approaches, weather modification, sustainability, etc. Agricultural water management increasingly must be integrated with other water management and environmental objectives. The main issues discussed in this paper are global water outlook, underground storage of water through artificial recharge, water reuse, non-point source pollution of groundwater, and virtual water.
2. Global population and water supplies
The present world population of about six billion is projected to almost double in the second half of this century. Almost all of this population increase will be in the Third World, where there are already plenty of water and sanitation problems and where about 1400 people (mostly children) die every hour due to waterborne diseases . Also, there will be more and more migration of people from rural areas to cities, creating many large cities including mega-cities with more than 20 million people that will have mega-water needs, produce