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Hydrology

Volume XVII |

Arch dam failure preliminary analysis using HEC-RAS and HEC-GEO RAS modeling. Case study Someșul Rece 1 reservoir

Abstract: This paper presents a preliminary analysis/simulation of the Someşul Rece 1 dam breaking scenario, from the homonym hydrographic basin, located in the north-eastern part of the Apuseni Mountains, at a 0.1 % probability tributary flow rate calculation. The study of the floodplain areas, that occur after the failure of the Someşul Rece 1 dam, was achieved with the help of 1D hydrological modelling. This type of modelling is one of the most complex (Cameron et al., 2006), involving both, the definition of a model with temporal evolution of the dam rupture, and the simulation of a unsteady flow stream in the downstream sector. For the dam analysed area and the downstream sector, several scenarios and modelling of hydrological systems was achieved, with the help of HEC-RAS 5.0.3 software, developed by the Hydrologic Engineering Center (U.S. Army Corps of Engineers).
This free software is the most widely used worldwide in the domain, particularly by the official agencies, having a continuous development, given by the involvement of specialists. The software simplifies the problem of hydrodynamic modelling, due to the limitation to a 1D model. Because the flood obviously has a spatial character, GIS software (ESRI ArcGis with the HEC-GeoRAS extension) were used in determining and defining the hydrographic elements (channel, talweg, banks etc.) and, also, in the representation of the results. Maps of the flood-prone areas have been developed, maps which indicated the magnitude of the estimated accidental flood downstream. The results of the simulation were also used to determine the anticipation time.

Volume XVII |

Playing with water – An introduction to experimental hydrology

Abstract: Water is the most important resource for the humankind, thus understanding hydrological processes could be con-sidered a vital task. Therefore, the main aims of this papers are to assess: (i) the current status of hydrologic field ex-periments; (ii) the techniques and the stages of the field hydrologic experiments at the microscale/plot-scale. Microscale hydrological studies are important both socially and economically as they emphasize the role of key factors (e.g. slope) in the utilization of water resources, the identification of critical hydrological thresholds for mobilizing, the propagation of soil particles in water flows and also the time it takes for pesticides, nutrients, and heavy metals to be mobilized. The key to conducting a successful hydrological microscale experiment lies in performing repeated attempts in the field. From an economic point of view, expedition (temporary) hydrologic field experiments are beneficial, as they shorten the working period and reduce the financial costs of the data acquisition process.
One of the challenges of experimental hydrology is the manipulation of “upscaling” or the statistical approach taken towards gathering and processing data.

Volume XVI |

Preliminary results in assessing flood-prone areas using UAS System within the Ozana River Upper Basin (the Eastern Carpathians)

Abstract: The UAV technique, and more recently UAS systems, play an ever important role in various domains of research and practical activities. The increase in number of publications focusing on their applicability is spectacular. The objective of this study is to highlight the efficiency of an integrated command-overflight-taking photo system, in an area with obvious problems related to hydric hazards and risks. The quasi-circular shape, the petrography of the upper Ozana basin, its orientation and its opening to the air masses predominantly movement direction, represent just a few of the reasons why it was chosen as the case study. Also, the settlements are displayed on the valleys thread, and this confluence has a remuu potential, in case of isolated rains in the two related subbasins. The UAV Phantom 4 quadcopter, the UAS system, the DroneDeploy application, the UAVPhoto application, the Visual-SFM application, the Daisy algorithm, the micro triangulation network (mesh), the work surface textures, a hyper-resolution of orthophotoplan, DSM model with a 5 cm resolution etc. are the technical elements that made modelling at a very high detail possible. The probability flow rates that were used, were provided by the two hydrometric stations located very close to the study area. Theywere calculated using professional applications approved at the national gauging network level, using the established Krițki-Menkel and Pearson III statistical distributions. The cross-section profiles was performed in the 10.x ArcMap module, using the 3D Analyst extension, and the hydraulic calculation to obtain the average velocity was done using the Manning equation; subsequently, the floodable surfaces was delineated on these profiles. Using the same ESRI module, the flood prone area polygon interpolation and it overlapping over the terrain model and over the orthophotomap were achieved. Paradoxically, the analysis of the results indicates a low degree of the anthropogenic habitat damage, but this aspect is due, in large measure, to the intervention of technical teams in the recalibration of the minor riverbed, massively clogged by alluvial transport.

Volume XVI |

Assessment of groundwater quality and its suitability for irrigation in Dindigul Corporation of Dindigul District, Tamil Nadu, India

Abstract: The Habitat Directive (HD) is the main strategy for nature The main aim of the study is to evaluate ground water quality suitable for irrigation purpose in Dindigul Corporation, Tamil Nadu, India. Within the study area 30 water samples were collected to determine the physical and chemical parameters. Sodium Adsorption Ratio (SAR), Sodium percentage (SP), Potential Salinity (PS), Residual Sodium Carbonate (RSC), Kelly’s Ratio and Soluble Sodium Percent (SSP) have been determined to analyze the irrigation water quality. The analysis results reveal that SAR value indicates 84% of excellent, 13% of good and 3% of unsuitable water category. Based on sodium percent, only 10% are good, 50% are permissible and 40% are unsuitable for irrigation. Based on PS and RSC ratio about 97% comes under unsuitable category and 3% are suitable water for irrigation. Kelly’s Ratio and SSP values indicate 27% of good quality and 73% are unsuitable irrigation water. The high concentration of salinity was found in the western part of the study area. The results show that most of the samples are not suitable for irrigation.

Volume XVI |

Aquifer Mapping and Characterization in the Complex Transition Zone of Ijebu Ode, Southwestern Nigeria

Abstract: Vertical electrical soundings (VES) and geophysical logs were employed to map and characterize the aquifer units in the Northwestern zone of Ijebu Ode, Southwestern Nigeria with a view to appraise the groundwater potential of the area. Sixteen Schlumberger soundings (VES) having maximum current electrode separation of 900 m were acquired and interpreted through partial curve matching and computer iteration. Gamma ray and resistivity logs acquired in a drilled hole were interpreted for aquifer characteristics. All but one sounding (VES 9), indicated signatures that are diagnostic of poor hydrogeological characteristics. Four layers were interpreted within 80 m depth. The first layer composed of topsoil (dry clay) which ranges in thickness from 0.8 to 1.5 m. Sandy clay (53 – 1895 Ωm) with varying thickness (0.8 – 34.5 m) constitute the second layer. Thick sand (2.4 – 55.3 m) having high resistivity (1208 – 7350 Ωm) make up the third layer. Resistive basement (3155 – 39529 Ωm) occurring at depth of 3 – 63 m constitute the fourth layer. The low resistivity sand (1023 Ωm) located beneath VES 9 was identified to be the saturated aquifer.  The saturated aquifer has 8 – 10% clay content and 40% porosity. The aquifer is 100% saturated with fresh water having resistivity of 122 Ωm and TDS value of 53 ppm. This study showed that the area was of low groundwater potential and highlights the significance of combined surface and subsurface geophysical investigations for groundwater in area where groundwater occurrence is erratic.