|CHAPTER 05: INLAND WATERS - INTRODUCTION|
Human health and development are threatened in many places because of insufficient or poor quality water. Flooding is a serious problem in some countries, and destruction of aquatic habitats by channelisation, rough maintenance schemes and damming of rivers can lead to an overall impoverishment of native plant and animal species.
By tradition most evaluations of the quality of the aquatic environment have been based on measurements of a set of concentrations, speciations, and physical partitions of inorganic or organic substances in the water. Other elements such as the amount of water and the physical conditions of the waterbody have only recently been considered to be of equal importance as the water quality per se for determining the ecological quality of the aquatic environment.
Demand for water of good quality has increased with the advent of industrialisation and rapid population growth. This trend has continued over time and has become more widespread geographically. In addition to domestic and industrial use of water, other requirements have become increasingly important. These include improved personal hygiene, agricultural irrigation and livestock supply, hydropower generation, cooling water for power plants and industry, as well as recreational purposes such as boating, swimming and fishing. Each of these intentional water uses affects, more or less, the quality of the water. Together with increased intensity of water use, discharge of untreated domestic and industrial wastes, excessive application of fertilisers and pesticides in agriculture, and accidental spills of harmful substances (including radioactive substances) have led to increasing pollution of many European waterbodies: groundwaters, rivers, lakes, coastal areas and seas. Figure 5.1 illustrates in chronological order the sequence of water pollution problems found in European freshwaters since 1850. Most pollution problems have evolved unrecognised over time until they have become apparent and measurable. Recognition of a problem, therefore, took considerable time and control measures took, in most cases, even longer.
Not all water quality problems are due solely to human impacts. Locally, natural geochemical conditions may cause high content of reduced iron (eg, in the Russian Federation and Denmark), fluoride (in Moldova and Bavaria, Germany), arsenic and strontium (in some mountainous countries), and salts in the groundwater, reducing its use as a source of drinking water. Natural events like volcano eruptions and subsequent mud flows, floods and droughts can lead to serious local and regional deterioration of the aquatic environment. The impact of some of these events, however, can be made worse by human activities; for example, by landuse changes, deforestation and river channelisation.
Water pollution used to be primarily a local problem, with identifiable sources of pollution by liquid waste. Up to a few decades ago most of the wastes discharged to waters came from animal and human excreta and other organic components from industry. In areas with low population density without sewerage systems, such problems are to a great extent alleviated by the natural self-purification capacity of the receiving water. However, with the increasing urbanisation of the 19th and early 20th centuries, and subsequent expansion of sewerage systems without any or adequate treatment, liquid waste loads have become so large that the self-purification capacity of receiving waters downstream of large human settlements can no longer prevent adverse effects on water resources. The results of discharges of such materials include dying fish, offensive smells and the risk of infection. In addition, the widespread channelisation of rivers that took place over this period contributed significantly to the reduction of the natural self-purification capacity of rivers.
Over the years, the pollution load of most receiving waters has further increased. In addition to impacts from point sources, pollution from non-point (diffuse) sources, for example leaching and runoff from agricultural areas and long-range transported air pollutants, have become increasingly important. Consequently, the associated problems are no longer just local or regional, but have become continental in scope.
For Europe, no general overview of water quality exists. Therefore, it is the main objective of this chapter and the following one to compile a picture, as comprehensive as possible, of the present state of European groundwaters, rivers, lakes, coastal areas and seas. Although the information available in many cases is anecdotal, an evaluation of water quality trends has been undertaken, and the present state of the waterbodies has been related to natural processes, and to human activities in the catchments overlying the aquifers or draining to the waterbodies in question.