We need 2 liters of water per day to meet our physiological demands. About 900 cubic meters of water per year are required to produce enough food for one person. However, water demand for 1,2 billion people worldwide cannot be met adequately. Freshwater shortage is due mainly to the growth of the world population (by 81 million people every year) and increasing water consumption. By water pollution water supply is further diminished. Despite increasing efforts to provide humanity with more water, per-capita water allocation has decreased since 1990. On a worldwide average, 70% of all freshwater is used for irrigation. As a consequence, freshwater supply is inseparably linked with food production. At present, at least one billion people on Earth are undernourished. Only 8% of all freshwater is used for domestic consumption, but water quality is not adequate, especially in regions with limited water availability. Insufficient supply with water of adequate quality is responsible for at least 5 million deaths every year. Mainly infants and small children are affected.
The overall amount of water made available for humanity can no longer be increased: This is because only water withdrawal from renewable sources is sustainable, and overall water renewal cannot be influenced by technical means. More efficient water usage is the only strategy available to us to improve the situation. The following measures are essential to overcome the global freshwater water crisis: (1) To minimize water losses, mainly for irrigation. Efficient irrigation technologies and water recycling are the most promising means to achieve this goal. (2) To improve water quality, mainly for domestic consumption. Water quality management of freshwater resources (surface waters and groundwater aquifers) as well as water purification are the best strategies to achieve this.