Geoinformation analysis of the satellite imagery data in order to assess the changes in radiohydrological conditions over the study territories

The article considers the relevance of the application of a set of terrestrial hydrological, radioecological and modern remote sensing methods in the process of monitoring studies of areas that are difficult to access, waterlogged, largely radionuclide contaminated. The example of the Ukrainian part of the left-bank Pripyat drainage system within the Chornobyl Exclusion Zone shows that remotely obtained data together with the materials integrated into the geographic information systems of the terrestrial measurements provide the adequate monitoring information on the spatio-temporal changes in the hydrological and radioecological situation in general. Among the research methods, the simulation, the methods of hydrometric, balancing, remote sensing studies of water bodies were most used. The main purpose of the research is to perform the retrospective and current analyses of the hydrological situation based on archival and recent satellite images, assess the effectiveness of the water protection complex on the left bank of the Pripyat River, especially after the introduction of hydrotechnical measures to improve its radioecological status. In the research process the LANDSAT, SPOT, IRS, WorldView images were used. In particular, a significant sensitivity of the "surface water – dry land" system to the changes in the environment of this area was established and the mapping of objects of open water surface was performed as well as its spatial and temporal variability was followed. When comparing the results of calculations of the radionuclides carry-over by water (in particular, 90Sr) before and after the implementation of appropriate measures at the water protection complex the notable negative consequences of its implementation and operation during a period from 1986 to 2001 were revealed. It was found that the diverted one-time 90Sr carry-over due to the construction of a "new" left-bank dam (according to the 1999 flood scenario) is "compensated" by 40% through the increase of its carry-over prolonged in time as a result of operation of the polder pumping station (PPS) and the inundation of the contaminated areas, which is caused by the complicated conditions for the discharge of surface and underground runoff caused by the "new" and "old" dams. The ecological advisability and validity of hydraulic measures (clearing of canals, reconstruction of culverts) and the recommended form of the operational complex (without the use of PPS, with natural filtration discharge of the body of the "new" sand dam in the Pripyat River) are confirmed by the results of thematic interpretation of the multiband images. Thus, within the complex, minor flooding and waterlogging of the inter-dam section, as well as areas to the north-east from the "old" dam are established. Prospects for the further research of various hydrological processes and radioecological situation on the left bank of the Pripyat River are seen in the use of high resolution remote surveys, which would be performed over the short periods of time. The informative result in good quality can be obtained on the basis of the use of unmanned aerial vehicles technology.