PREDICTION OF RADIOACTIVE CONTAMINATION OF WATER BODIES AFTER THE CHERNOBYL ACCIDENT

To predict radioactive contamination of rivers, reservoirs and lakes a fter the Chernobyl accident, a number of mathematical models have been developed. These models described the processes of radionuclide washo ut from catchment areas and their migration in bodies of water. It tur ned out that the radionuclide exchange in the systems of water-bottom sediments and surface run-off catchment area soil contributed greatly to contamination of water. As was shown by the post-Chernobyl experien ce, it is rather difficult to specify the parameters needed. Starting in 1991, a comprehensive monitoring of water and sediment contaminatio n with radionuclides, as well as their washout from the Iput river cat chment area was organised in order to test the prognostic performance of the models. The data obtained proved to be most useful for studying a long-term contamination of rivers and testing mathematical models. A thorough account of the basic physical features of the radionuclide exchange in the systems of water-bottom sediments and surface run-off in the models enabled one to describe adequately the behaviour of radi onuclide concentrations and provided a good agreement with observation al data.