Water and sea management
The threats to surface waters are connected with the development of civilization. They result from extensive exploitation of natural resources, chemicals use, air pollution, and different water-management activities.
Surface waters are very important to biological diversity as they offer rich set of habitats for many species and form a spatial system covering the country and the continent with the network of connections, which perform the functions of ecological corridors. It is especially important as we can observe the increase in habitat fragmentation in our as well as other European countries.
Poland is poor in water. Only 1660 m3 water fall for one citizen - over three times less than on average in Europe and over five times less than on average on the Earth. This state is deepened by considerable diversity of outlet in particular years. Moreover, a big part of outlet is seasonal – in the same year and in the same area, there may be alternately droughts and catastrophic floods. Additionally, little water resources of Poland are very unequally placed.
Because Poland is poor in water, water-management activities aim at providing people with water, protection against floods and regulation of water regime in agricultural land. Such actions are performed through transformations in water networks, river regulations, building water reservoirs and embankments. Undoubtedly this is a strong intervention into natural ecological systems. Its effect are transformation of landscape and changes in natural environment, and what follows - the decrease in biological diversity in Poland .
The main usages of surface waters are water consumption for household, farming and industrial purposes as well as for keeping sewage from factories. Industry is a main receiver of water; at present, it uses about 70 % of collected waters. In that, power industry has the biggest demand for water as it uses about 89 % of waters collected for industrial purposes.
Over 4/5 of collected water come back as sewage to the environment, especially to rivers. Some of it does not need purifying but it has influence on physicochemical processes and biological ecosystems where it is introduced. The rest of sewage – in 2001 2.4 km3 -needs treatment. From that 90% are purified, although not always enough, and the rest goes to surface waters without treatment. The biggest problem constitutes agricultural land where most sewage goes to the waters without any purifying at all. This causes a threat to the functioning and durability of ecosystems. To the main dangers belong:
- Saprotrophication of waters as a result of organic matter accumulation,
- Eutrophication of waters as a result of nutritive substances supply,
- Contamination of waters as a result of toxic substances introduction.
Activities aiming at waters protection in 1992-2001, such as e.g. building many sewage treatment plants, stopped the pollution of Polish main rivers, which was growing for years. In recent years, a principle of water management in water catchment system was introduced in Poland (Water Law from 2001). This is a basis for an integrated management and a rational use of water resources.
Biological diversity of the Baltic Sea is connected with various man's activities within the basin and with the pressure of water catchment. Activities within the basin comprise building, conservation, and exploitation of water routes, development of harbours, exploitation of mineral and biological resources and others. Water catchment may endanger the quality of water, and increase eutrophication and pollution. The quality of waters introduced by the Vistula and the Odra has a significant influence on the purity of Baltic water, especially in coastal zones. The rates of water quality in the Baltic Sea change periodically but for the last 10 years the general quality of waters has not changed considerably. A local improvement was noticed only in a coastal zone.
Despite long-term efforts of the Baltic Sea Region countries, the quality of the Baltic Sea becomes unsatisfactory. Much pollution is still flowing into the sea. The chance for the improvement of water quality is building new sewage plants and modernising the old ones, which is included in Polish plans for the next years until 2015.