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Hydrology

Volume XX |

Analysis of the Relationships Between the Phreatic Aquifer and Natura 2000 Habitats from ROSCI0224 Scroviștea

Abstract: The analysis of the relationships between groundwater and terrestrial ecosystems contributes to the conservation of biodiversity and the quantitative and qualitative status of the aquifer.
The main goal of the paper is to analyze the relationships between the phreatic aquifer of ROIL16 (Vlăsia Plain) and the six Natura 2000 habitats from the Site of Community Importance (SCI) ROSCI0224 Scroviștea.
This work is based on hydrogeological, geological data, mathematical modeling of the phreatic aquifer (October 17-19, 2017), and the methodology used for study the relationship between groundwater bodies and terrestrial ecosystems, developed by the R.A.H. (2015).
The evaluation of the dependence (high – A, medium – B, nule – C) relations, between the phreatic aquifer and the habitats, is made mainly by correlating the depth of the hydrostatic level with the depth of the root system of plant and tree species.
The main findings based on the hydrogeological, ecological criteria, and analysis algorithms highlight the fact that most habitats and later the Scroviștea site are dependent on groundwater. The six Natura 2000 habitats (3150, 3160, 91M0, 91F0, 91E0 și 92A0) are analyzed individually concerning the depth of the groundwater level. In the evaluation of the degrees of dependence of the habitats, two other criteria are applied, maximum and arithmetic mean about their extension surface. Thus, four habitats (91M0, 91F0, 91E0, and 92A0) are identified with high dependence on groundwater, and two habitats (3150 and 3160) with nule dependence. Considering only this stage of analysis, it was considered that the SCI Scroviștea has a high dependence on the phreatic aquifer.
For a correct assessment of the dependence relations between groundwater and habitats, analyzes related to the hydrodynamic and hydrochemical regime of the groundwater aquifer and the correlation of this information with analyzes from specialized studies performed for plant and tree species are required.

Volume XIX |

Flood Mapping and Estimation of Flood Water-Level Using Fuzzy Method and Remote Sensing Imagery (Case Study: Golestan Province, Iran)

Abstract: Recently, the heavy precipitation occurred across the north of Iran caused an unprecedented flood. Due to the topographic conditions of the study area, not paying attention to the regular dredging of the river has caused a lot of problems for the local people. On the other hand, due to the frequent rainfall, the occurrence of flooding for a long time was another major problem. The combination of Remote Sensing and GIS can make a substantial contribution to flood assessment and management. In the present study, a fuzzy method is developed to show the hidden potential of Landsat satellite images for flood mapping. This paper presents the process of rapid access to water level information, which can provide valuable data for decision makers. The overall accuracy obtained for the flooded and damaged area is 87.23% and 46% respectively, and Root Mean Square Error (RMSE) of 27.68 cm is obtained for water-level based in the proposed algorithm.

Volume XIX |

The Buzău river alluvial fan – a groundwater modeling approach to sustainable exploitation

Abstract: Knowledge of groundwater resources is a key challenge for hydrogeologists, especially due to a continuous increase in demand for drinking water. This paper aims to investigate the consequences of overexploitation of the phreatic aquifer from the Buzău River alluvial fan and to assess alternatives operating programs related to achieving a sustainable groundwater exploitation. The study was achieved using data (groundwater level and general information from 97 hydrogeological boreholes) from the National Institute of Hydrology and Water Management, Romania, and collected in the field between July 18-19, 2017 (river stages for Buzău and Călmățui). The aquifer data was statistically analyzed and the obtained results allowed the design of a conceptual model for the hydrostructure and a mathematical model for the groundwater flow, using the FREEWAT software. Continuous exploitation of the phreatic aquifer through the catchment fronts that supply the city of Buzău (Crâng, Zahăr I, and Sud fronts) was simulated using the hydrodynamic model, in a transient regime. The maximum allowable flows were defined for each hydrogeological borehole that exploits the phreatic aquifer, using the mathematical model (values between 4.0 and 19.0 l/s). The exploitation of these flows was performed for 10 years, with time steps that allowed an analysis of the depression cone extension and drawdown value after 90 days, 180 days, one year, and five years of continuous pumping. After ten years, the resulting depression cone reached a diameter of 9.8 km and the groundwater level decreased with a maximum of 8.26 m, in a hydrogeological borehole. For stationary simulation (which is not influenced by the time parameter), it was observed that pumping with the maximum allowable flows resulted in a drawdown that exceeds one-third of the water column, which indicates overexploitation.

Volume XIX |

The occurrence of the armored mud balls during the flash flood phases of the streams from the Meledic Plateau – the Curvature Subcarpathians, Romania

Abstract: Armored mud balls that form in fluvial environments were observed on the river bed of two small streams from South-East Subcarpathians Bend, in the area of Miocene deposits with salt dia-pirs. Pieces of well-rounded clay mate-rial but with coarse surface were found on the gravel banks as well as partially submerged into stream channel and embedded in soft sediments of stream banks. The surfaces of mud balls, nearly spherical and ranging from 5 cm to 17 cm in diameter, were studded with sand grains and gravel that collected during flash floods as a result of bedload transport. The main source material of the armored mud balls consists of dark clay material detached from the cap rock of the salt massif that is crossed by the two streams. The newly formed armored mud balls, which were found among the gravels on the stream bed following the summer flash flood event from June 2019, supports the fact that these particular sedimentary features form during exceptional floods when pieces of clay material are rolled by the high-energy water flow, which results in acquiring of their spherical shape and the pebble shell. This paper represents the first report on the occurrence of modern armored mud balls formed in a fluvial environment, located in the Curvature Subcarpathians, Romania.

Volume XIX |

On the linear trends of a water discharge data under temporal variation. Case study: the upper sector of the Buzău river (Romania)

Abstract: The aim of this paper is to provide a statistic overview of the hydrological impact of the Siriu Dam on the Buzau River (Romania), taking into account the temporal variations. Our case study uses the daily mean discharges of the Buzau River (1st of January 1955 to 31st of December 2010), registered at Nehoiu hydrometric station. The building of the Siriu Dam in 1984 required the division of the study interval into two sub-periods, each being analyzed annually and seasonally, on the series themselves or on the pre-whitened ones when prior required. The existence of a linear trend on different periods and sub-periods has been studied by using the Mann-Kendall and Seasonal Mann-Kendall tests. In the case of the existence of a linear trend, the slopes have been calculated with Sen’s Slope Estimator. The stationarity has been studied by using the Dickey-Fuller and Kwiatkowski–Phillips–Schmidt–Shin tests. According to our preliminary results, the stationarity in trend after the dam’s construction, respectively increasing linear trends for almost all the data series and subseries was observed. The trend and stationarity outcomes proved that the Siriu Reservoir has a good impact on the homogeneity of the Buzau River’s discharge and the increasing trends are related to human activity impact coupled with climate change/variability.