This article identifies and analyzes the effects of human pressures on the river systems, landscape, flow regime, and water quality in the Bucharest region, the largest urbanized area in Romania. The analyses focused on four streams crossing the Bucharest region, namely the Dâmboviţa, Colentina, Argeş, and Sabar rivers. Our approach relied especially on three types of information: (1) spatial data; (2) hydrological data sets; and (3) water quality data. We made a diachronic analysis of the available maps and ran classic statistical analysis of the data sets, as well as trend analysis. At the same time, we compared the flows in natural (reconstituted) and modified (current) regimes. The results showed that the stream system and its associated landscapes have considerably changed due to several engineering works (reservoirs, dams, channelization works, diversion canals, water intakes, etc.). Under these circumstances, the flow regime suffered changes that differed among the rivers. Thus, the multiannual discharges of the Argeş and Dâmboviţa rivers did not exhibit significant changes, but only mitigated the monthly discharge variability. In the case of Sabar and Colentina, a significant increase of the annual and monthly discharges was identified, due to the water transferred from the neighboring rivers. Water quality worsened, especially on the lower courses of the Dâmboviţa and Argeş rivers, degrading the states and health of the aquatic ecosystems in the study region.

Evaporation and evapotranspiration are major components of the water cycle and water balance. Studying them allows a better knowledge and understanding of the mechanisms and regularities that guides the water circulation in nature and also its associated processes. The general aim of this study is to analyze the evaporation and evapotranspiration measured on the Căldăruşani Lake, and their influence on the lake's water volume. The paper highlights: i) the temporal variation of the measured values of the evaporation and evapotranspiration and the influence of some controlling parameters (mainly climatic) on these processes; ii) the relationship between the evaporation and evapotranspiration; and iii) the volume of water loss by evaporation and evapotranspiration, influencing the lake's water resource. The study is based on climatic, hydrologic and morphometric data of the Căldăruşani Lake. The analysis is performed for the 2009-2014 period by using statistical and mathematical methods (for example, linear correlations or equations to estimate the volume of water loss by evaporation). The results show higher values of the evapotranspiration (10.3mm/day) than those of the evaporation (4.3mm/day). The volume of water loss by evaporation and evapotranspiration from the Căldăruşani Lake, in 2014, was around 2.9 mil.m3 (almost 1/3 of lake's volume)

This paper aimed to investigate the dominant runoff processes (DRP’s) at plot-scale in the Curvature Subcarpathians under natural rainfall conditions characteristic for Romania’s temperate environment. The study was based on 32 selected rainfall-runoff events produced during the interval April–September (2014–2017). By comparing water balance on the analyzed Luvisol plots for two types of land use (grassland vs. bare soil), we showed that DRP’s are mostly formed by Hortonian Overland Flow (HOF), 47% vs. 59% respectively. On grassland, HOF is followed by Deep Percolation (DP, 31%) and Fast Subsurface Flow (SSF, 22%), whereas, on bare soil, DP shows a higher percentage (38%) and SSF a lower one (3%), which suggests that the soil-root interface controls the runoff generation. Concerning the relationship between antecedent precipitation and runoff, the study indicated the nonlinearity of the two processes, more obvious on grassland and in drought conditions than on bare soil and in wet conditions (as demonstrated by the higher runoff coefficients). Moreover, the HOF appeared to respond differently to rainfall events on the two plots - slightly longer lag-time, lower discharge and lower volume on grassland - which suggests the hydrologic key role of vegetation in runoff generation processes.