HUMAN life is dependent on the presence of fresh water. Of the approximately 1.4 billion cubic kilometres of our planet's water supplies fresh water makes up less than three per cent. Most of this is tied up in glaciers, ice caps and snow fields, particularly in Antarctica. Only a tiny fraction of the Earth's fresh water reservoirs is easily accessible for human use. Lakes, wetlands and rivers, however, do not comprise the remaining major fresh water compartments. The continents of our planet are blessed with more than thirty times as much ground water as surface water.
Public opinion, however, is only too often preoccupied with the more obvious 'visible' surface water sources when it comes to water pollution, counter measures and restoration. This is at least partly due to their recreational value. Over the past few decades, the media in Germany, for example, have focussed especially on the water quality of German lakes and rivers which in some instances has indeed improved substantially. At the same time, the constant deterioration of the quality of ground water as a result of acidification and rising nitrate levels has been neglected almost completely.
Until very recently ground water has been thought of as being a standard of water purity in itself. And to a certain extent this is indeed true. Ground water is precipitation that does not evaporate or run off into a river but percolates through the soil and permeable rocks until it is held back by an impermeable layer of rock or clay. This process, which is called infiltration, along with the constant rising and falling of the water table and the length of time which infiltrated water stays and moves in the ground, all this ensures--under normal conditions--a high degree of purification.
Many modern pollutants, however, are extremely stable and the fact that it takes up to …