Chemical substances, bacteria's and different microorganisms the dirt of waters be caused mainly, present in natural waters in enlarged quantity. Chemical organic substances and inorganic (mineral) they step out in figure of solutions, colloidal solutions and suspensions. The natural factors, np. the chemical composition of dirts be shaped with disposal from soils and rocks the substance, development and necrosis the water organisms as well as anthropogenical factors. Pesticides to the most often the stepping out anthropogenical dirts of superficial waters belong, powierzchniowo active substances, hydrocarbons ropopochodne, phenols, chloric derivatives as well as metals heavy bifenylu: (Pb), (Cu), (Cr), (Cd), (Hg) and (Zn), and also heated up waters ( thermal dirt), which they are particularly dangerous for waters superficial about small flow or standing waters. The majority of anthropogenical dirts of waters acts on water organisms toksycznie. Dirt very durable in water environment and subject chemical and biochemical processes very hard refakcyjnymi be calls substances. The most dirts hit to waters from sewages together. They are different sources of dirts of waters water transportation and land, applying and fertilizers artificial pesticides as well as municipal wastes and industrial. The waters undergo the dirt in result of eutrophication also. The circulation of water in nature was disturbed by man - the cutting out the forests, monoculture of agriculture the, inappropriate and excessive agricultural interventions, the urbanization.