This chapter is to evaluate quantitative and qualitative conditions of water resources in Bulgaria during the 1982-1994 drought and to use this period as a model for future climate change. In Bulgaria, precipitation and air temperature data are available from 1892 to the present, river water levels from 1909 and systematic water discharge measurements from 1936. The water regime in Bulgaria is described in territorial and temporal units in relation to climate, hydrographic conditions and natural chronological variations. The objective of analyzing the chronological variations in river runoff and elements of the water balance, precipitation and evaporation, is to generate possible scenarios of global climate change. In the preliminary analysis of annual river runoff data, regression and correlation analyses between annual and total chronological values of discharge, precipitation, and air temperature for the three main hydrological zones were used. In addition to investigations of river runoff and precipitation, the analysis of variations of groundwater during the drought period was considered.