ИСТИНА

It was found based of detail study of sediment redistribution and Chernobyl-derived Cs-137 lateral migration along pathways of fluvial system of Central Russia, that for present-day climate conditions and land use the most part of Cs-137 redeposited within small catchments with area less 50 km2. Low toes of cultivated slopes and dry valley bottoms are the main sinks of 137Cs. Because of that total Cs-137 inventories in given locations do not decrease if compare with initial Chernobyl fallout values or even increase in some places Relatively small proportion (1-10%) of Chernobyl-derived Cs-137 are transported to the river channels of the river with basin area > 100 km2. However in some cases it may promoted to serious increase of radionuclide contamination of river floodplain and reservoir. The main factors influenced on intensity of Cs-137 lateral migration in the Central Russia are following: area of cultivated lands, dry valley density, LS factor, surface runoff coefficient during snow-melting, occurrence of high intensity rain, soil conservation measures and cultivated-slope – river channel connectivity.