The chapter presents the problem of drought and describes its classification and methods of assessing this risk. The aim of this chapter is to identify statistically significant trends in streamflow characteristics of low water content in the Eastern Slovakia, which are used in the evaluation of hydrological drought. In this thesis is presented a new methodology for evaluating hydrological drought based on statistical analysis of observed minimal flows at selected 63 gauging stations in Eastern Slovakia for a 32-year period. Mann-Kendall statistical test identifies the frequency of minimal flow trends: in individual gauging stations, in river basins (Poprad, Hornad, Bodva, Bodrog to throughout Eastern Slovakia), and also in groups of gauging stations with the same physicogeographical parameters. Size of the flow trends is identified by directives of the trend lines. The procedure is also applied in assessing the impact of human activities and the impact of physicogeographical factors for the emergence of hydrological drought. Obtained results from the statistically significant trends in the flows are established prediction of hydrological drought risk in each month of the hydrological year in Eastern Slovakia.