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Hydrology

Volume XV |

Spatial and temporal dynamics of human pressure within the Preajba catchment area, Romania

Abstract: This study refers to the spatio-temporal dynamics of human pressure in Preajba basin, located in the southeastern part of Craiova municipality. The statistic and cartographic analysis is based on the determination of a variety of environmental indices: index of human pressure by demographic dynamics, index of human stress through agricultural land use, naturality index, artificialization index and environmental change index. Choosing a grid of 1.5 sqkm for calculating and comparing the artificialization index of the landscape allows a concise analysis on the environmental transformation in the above-mentioned area. Complementary, temporal dynamics of the environmental indices values is highlighted by the choice of some benchmark years, i.e. 1992, 2002, 2012, 2014 to which data and recent cartographic materials from 2009 and 2014 are added. Results, materialized in the obtained values present the state of the environment and the human pressure implications on the Preajba lacustrine ecosystem (maximum values obtained at period level): physiological or agrarian density – 52 inhabitants/ha in 1992 (Craiova); human pressure index through arable – 1.4 ha/inhabitants in 1992 and 2002 (Malu Mare); naturality index of the landscape – 9.43 in 1992 (Malu Mare); environmental change index – 3.69 in 2012 (Coşoveni). Field campaigns conducted in 2015 and 2016 confirm the research results and visually support human pressure on the environment. The proposed measures, in order to stabilize and maintain the good environmental quality in the Preajba basin targets the lacustrine ecosystem by involving local authorities in order to protect the avi-faunistic natural area status of “Preajba-Făcăi Lacustrine Complex”.

Volume XIV |

The temporal variation of suspended sediment transport according to the dominance of suspended sediment sources. Case study: the Trotuş river between 2000 and 2014

Abstract: Based on the data series of average daily streamflow and suspended sediment load recorded between 2000 and 2014 at four gauging stations (Lunca de Sus, Goioasa, Târgu Ocna and Vrânceni), the temporal variation of the suspended sediment transport was investigated according to the prevalence of source areas. Thus, a significant temporal variability (monthly, seasonal, annual) was determined, in close relation with the amount of precipitation and the streamflow. The following equation was determined between the mean monthly suspended sediment load (Ṝ) and the mean discharge (Ǭ) at Vrânceni section: R= 0,0035Q2,2895, r=0,899. We believe this relation has a high degree of confidence for the indirect determination of solid load and it is comparable with other equations of this type. Along the entire length of the river, July was the month during which the highest suspended sediment load was recorded, with an average percentage of 37% of the total amount. At the opposite end, December is the month with the lowest documented suspended sediment load, with just 0.5% of the total amount transported annually by the Trotuş. As regards the seasonal variability of the suspended sediment load, the following values were determined along the entire length of river Trotuş: during the winter season the volume of sediment carried by the river amounts to approx. 2.1% of the total annual transported suspended sediment, the spring season accounts for 33.7% of the annual volume, the summer season accounts for ca. 55.5%, and the fall for 8.7%. In order to plot the R-Q correlation, the wettest, as well as driest years were selected for every gauging station. On the resulting plots, there were identified the thresholds based on which the two sources were separated depending on the area of origin: dominant from the catchment or dominant from the river bed. Overall, during the investigated period on the Trotuş river, the river beds contributed with about 21% of the total volume of transported suspended sediment. Depending on the type of the year (wet, dry or normal), the average input of the beds to the annual volume of suspended alluvium was as follows: 4% in wet years; 43% in dry years; 15% in normal years. The total volume of suspended sediment transported through the four sections on the Trotuş river between 2000 and 2014 amounted to approx. 39×106 t, thus the average annual volume was 2,598,000 t. A large share of this suspended sediment yield was produced during major floods. For example, at Vrânceni ca. 61% of the total sediment yield for the 15 year-period under investigation resulted from just 3 flood events (2005, 2010 and 2012).

Volume XIII |

Seasonal river flow variability of the Middle and Lower Danube and its tributaries

Abstract: The seasonality of stream flow variability indicates special feature of local cycle of precipitations, evaporation and the timing of snow melt. This study presents seasonal occurrence of maximal and minimal annual flows and spatial variability of seasonal index (Is) in the Middle and Lower Danube basin. The analysis is based on 47 time series of monthly runoff (12 for the Danube and 35 for its tributaries), which are collected from public database. The results show that the maximum annual stream flow appears during all months, but with highest frequency in April for 68% from watersheds. It varies between one and 60% (Danube – Baziaz). The monthly flow is concentrated in summer–autumn hydrological season, except for the Jalomita, Siret and Prut river basins, where it is in the winter. The highest frequency of minimum monthly runoff for the Danube and the Tisza is in October and November and for the Sava and Velika Morava – in August and September. The lowest and highest monthly discharge of the given month in the entire period were recorded in different years. Seasonal index (Is) is between 0.98 and 3.18. It is about 1.00 for the Danube and more than 2.00 for the Tisza, Ialomita, Siret and Prut watersheds. Is is stability – coefficient of variation is up to 0.30 with the exception of several river basins. Stream flow variability of the Middle and Lower Danube can provide valuable information for scientific studies and integrated management of water resources.

Volume XIII |

Analysis of River regime and Water balance of the Temštica River Basin (South-East Serbia) during the 1980-2012 Period

Abstract: In this study we analyze river regime and water balance of the Temštica River on the base of thirty three year (1980 – 2012) data series. For this study period, the mean water level of the Temštica River was 41 cm. The average discharge of the Temštica River at Staničenje station for the investigated period is 5.63 m3/s. Annual changes in average discharge is similar to the annual course of mean monthly low and high discharge values. It is concluded that the Temštica river has moderate – continental river regime. Although the precipitation quantity is not so low – 596 mm per year, of which 217.05 mm or 36.42 % of it runoffs, and 378.92 mm, or 63.58% evaporates. The ratio of the components of the water balance in the basin is not convenient, appropriate measures to improve the situation in this river basin should be taken.

Volume XIII |

Research of water balance at hydrological micro-scale in the Aldeni experimental basin (Romania)

Abstract: The paper presents a number of aspects regarding the Aldeni Experimental Basin (Romania). In order to experimentally investigate micro-scale (plot scale) hydrological impact of soil erosion, the National Institute of Hydrology and Water Management founded, in 1984, the Aldeni Experimental Basin (AEB). AEB is located in the Curvature Subcarpathians, a region characterized by a sharp erosion of soil. Experimental investigations at a micro-scale are aimed towards: determining the parameters of the water balance equation, during natural and simulated rainfall; researching of runoff genetic and soil erosion processes on runoff plots; extrapolating relations involving runoff coefficients from a micro-scale to meso-scale. Runoff plots have A = 80 sq m (20 x 4m), WNV-ESE aspect and an average slope of 5.6%; one runoff plot is maintained with grass, and the other is devoid of grass by digging (processing) and the structure of the first horizon with a depth of 20 cm has been changed, which resulted in a greater development of infiltration than in the first runoff plot. Complex measurements and sampling observations of the necessary elements for the quantitative estimation of the water balance equation are achieved with the help of specific equipment on standard climatologic and hydrological time (hourly and pentads) at hydrometric stations and meteorological platform, while at runoff plots scale per rainfall event. Nowadays, the latest evolutions in data acquisition and transmission equipment are represented by sensors (such as sensors to measure the soil moisture). Exploitation and dissemination of hydrologic data is accomplished by: research themes/projects, yearbooks of basic data (Experimental Basins Yearbook) and scientific papers.