Topicality. Preservation and increasing of soil fertility is the essential problem for the agricultural melioration. It was solved in the most intensive way during the period of 1960s-1980s within the framework of “Large-scale program of the melioration development”. Poor technical condition of the internal economic network of Dnipropetrovsk Region is peculiar for more than 136 thous. ha being 68.6 % of the irrigation land area. That results in considerable filtration losses, which stipulates both increased prime cost of the irrigation water and deterioration of environmental and melioration conditions of the neighbouring territories. For a long time, reconstruction of the irrigation system has not been financed properly. Implementation of the measures aimed at restoration and development of irrigation is one of the priorities of the Agreement on the Association between Ukraine and the European Union. Nowadays, much attention is paid to diagnostics of technical state of hydroengineering structures (HES) in melioration systems of CC1 structure category (especially, to the retention basins of irrigation systems) involving non-destructive instrumental methods. According to the recommendations of normative documents, it is proposed to determine the zones of increased filtration within the earth dam body, protective dams, and reservoir beds using a system of geophysical methods including the following ones: vertical electric sounding (VES), microelectric sounding (MES), electric profiling (EP), and method of natural electric fields (NEF). Unfortunately, the mentioned methods are often rather cost- and labour-consuming ones. That emphasizes the topicality of developing and implementing the innovative methods for complex evaluation of technical condition and detection of hidden filtration zones within the bodies of earth HESs. That will help localize and maintain timely the identified site making it possible to prolong operation period of the object and prevent rise of ground water level within the neighbouring territories. Objective of the paper is experimental substantiation of the efficiency of using labour- and time-saving geophysical NPEMFE method to detect filtration and watering zones, being undetected visually, within the hydroengineering structures of melioration systems to improve their operational qualities, reduce their maintenance cost, and prevent deterioration of environmental and melioration conditions of the neighbouring territories. Research methodology. The following conventional methods were applied during the scientific and engineering survey activities: field – geophysical research methods NPEMFE and VES to determine filtration zones, which were not detected visually; experimental – involving odometer of standard modification to detect electromagnetic radiation during the loading of loose argillaceous soil samples; laboratory - standard techniques to specify physical and mechanical properties of soils before and after their compressive studies; computational-analytic – to determine dimensions of filtration water losses from the basin. Golden Software Surfer 8 and AutoCad 10 programme complexes were applied to process the obtained results. Scientific novelty of the research results. For the first time, it has been proved experimentally that electromagnetic radiation increases when loaded with loose argillaceous samples and decreases when the samples are moist. That makes it possible to apply the NPEMFE method to identify visually non-detected filtration zones within the body of hydroengineering structures of melioration systems. Practical value of the research: possibility to use time- and labour-saving NPEMFE method to identify visually non-detected zones of filtration and watering within the body of hydroengineering structures in melioration systems of CC1 structure category has been substantiated experimentally.