Loess and loess-like sediments cover approximately 13% of the Bulgarian territory, mainly within the Danubian plain. From the Danube River to the Fore-Balkan, the loess soils form a loess complex where its depth varies from 50–60 meters in the north to few meters in the south, respectively. Widespread loess sediments possess a specific feature: they typically form deep unsaturated zones. Quantification of the near surface water balance is extremely important for evaluating land-atmosphere interactions, and the impact of land-use change on the subsurface flow and the evapotranspiration rate is an essential term in this quantification. In the frames of a scientific project, an automatic weather station was installed in a typical plain terrain of the loess complex in Northeast Bulgaria, recording meteorological data from September 2015 to February 2017. This study provides a mathematical description of processes (i.e., Penman-Monteith and Hargreaves Methods) used to estimate daily evapotranspiration rates implemented into the numerical model HYDRUS-1D, as well as a respective rate investigation of months with and without intensive rainfalls. Overall results indicate that using the Hargreaves formula for evaluation of the potential evapotranspiration leads to overestimation between 10% and 20%, respectively for a “wet” and “dry” month.

No abstract

After Bulgaria’s accession to the European Community, a process of harmonization of national legislation with the European Union has started. This has led to the introduction of the term “groundwater bodies”, sometimes resulting in conflicts between hydrogeologists and water management experts. Some examples are considered in this respect, relating to the boundaries and extent of groundwater bodies, assessments of their quantitative and chemical characteristics, interconnections with surface waters and ecosystems. To overcome these problems, it is necessary to have a much better interaction between hydrogeologists from science and practice, on the one hand, and water management experts.

Flooded abandoned coal mines are a potential source of geothermal energy, which could be used for heating and cooling of energy efficient buildings. Cherno More Coal Mine is located in SE Bulgaria and has been closed for more than 20 years. It represents a large human-induced subsurface reservoir which consists of three interconnected coalfields ("Brigadir", "9.IX." and "Blagoev"). Their total volume of about 2.0 × 10 6 m 3 has been calculated considering the size of the stone drifts. The mine water temperature is measured to be about 16 • C in the only accessible vertical shaft ("9.IX." coalfield). This is the first study of an abandoned coal mine in Bulgaria aiming at assessing its low-valued energy potential and evaluating the opportunity for heating and cooling buildings. The geological and hydrogeological characteristics of Cherno More Mine have been analyzed by using existing archive data and conducting additional chemical analysis of water samples and temperature measurements in the mine. The obtained data were used to develop a regional groundwater model of the The funding from the European Commission (CONCERTO II) for carrying out the survey is gratefully acknowledged. 565area and a local hydrothermal model for a thermally-insulated furniture factory located in the vicinity of the vertical shaft. The simulated temperature distribution in the mine during exploitation showed no impact on the production temperature by reinjected water under defined steady state conditions, which created a reliable basis for mine water energy use.

The human impact on the environment as a result of natural goods mastering often leads to contamination of wide areas. Example for that is the work of “Cumerio—Med” AD factory, situated between Zlatitsa and Pirdop towns. The hydrodynamic modelling shows the tendencies in groundwater movement in the investigated area. Simulation of pollutants migration for different periods have been made — copper and sulfates. The issue is fast transport of sulfates in comparison with copper.