This work analyses changes in the content of nutrient components and trace metals and metalloids at three tributaries of the Maritsa River flowing in Southern Bulgaria with catchments affected by mining and agricultural activities. Input data includes information about 14 chemical water quality parameters (N-NH 4 , N-NO 3 , N-NO 2 , N-tot, P-tot, P-PO 4 , Al, As, Fe, Cu, Mn, Ni, Pb, and Zn) obtained from the Executive Environment Agency for the period 2015-2018. Two documented methods were used in this work to determine the pollution status of river waters-Heavy metal pollution index (HPI) and CCME Water Quality Index. The results based on the CCME WQI ranked water quality as "Poor" (WQI values range from 31.2 to 39.9). The HPI ratings achieve scores exceeding the critical pollution value of 100 for some of the metals (Al, Cu, Mn, and Zn), which indicates that water is seriously polluted concerning those variables. Therefore, it can be summarized that the river waters are not appropriate for safe drinking , agriculture, and household use because of significant nutrient and metalloids and trace metalscon-tamination.

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Annual streamflow of Bulgaria in the beginning of XXI century. Estimating the annual streamflow under the climate change is a challenge for hydrology science and an important task for geography as well. There is no analysis about the basic statistical parameters of the annual runoff time-series after 2000 in scientific investigations in the country. This paper describes Bulgaria's annual streamflow during 2000 -2016 for the main catchment areas in the country (Danube watershed, Black Sea catchment area and the Aegean Sea watershed). The work is based on publicly available data of annual streamflow. The screening of the hydrological data for homogeneity, randomness, probability distribution and the trend is based on statistical methods. The obtained results show regional differences in scale of fluctuation of hydrological variables around the norm for the referent periods, in the years with maximum and with the minimum volume of the water resources, in the probability distribution of empirical data. All timeseries are homogeneous, randomly and with the absence of the trend. The work draws a conclusion that annual streamflow of main catchment areas of Bulgaria in the beginning of XXI century is in the normal frame and with larger fluctuation than the referent periods and that the time-series statistical models need confirmation using the larger base of hydrological data. This work is the first estimation of the annual streamflow during XXI century in Bulgaria by major watersheds and it gives a new information about hydrological processes in the country.

High flow events are the main prerequisites for floods with negative social and environmental consequences. Their study under uncertain and changing climate gives informative knowledge for further management decisions. This paper seeks to analyze the spatio-temporal parameters of high flow periods within the Danube drainage basin in Bulgaria. Three characteristics of the hazard phenomena: time of occurring, frequency and duration are investigated. The analysis is based on daily discharge data collected from 20 gauging stations for the period 2000–2005. The surplus water quantities are identified by the Threshold level method using fixed values – Q25 and Q5, derived from the flow duration curve. Results show a concentration of the high flow periods during the spring hydrological season, with an average duration up to six weeks. The calculations establish positive correlations between the duration of high flow, the altitude of catchments, and the density of drainage network. The resulting information can serve as a support for the development of preliminary flood risk assessments in the Danube River Basin.