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Hydrology

Volume XV |

Evaporation and evapotranspiration in Romania

Abstract: Evaporation and evapotranspiration are two of the most important elements for achieving a comprehensive study of water balance components and of conceptual hydrological models, lately becoming parameters of great interest in research on climate change. This study can be used for determining of evaporation and evapotranspiration rates at micro-scale using indirect methods. The importance of this study consists in identifying the regions exposed to significant water release in terms of water evaporation and evapotranspiration, in order to improve the practices and methods of water reserve management nationwide. In Romania, the spatial distribution of the analyzed variables is, for the most part, determined by the relief, which constitutes the main factor that dictates the particularities of both the local and regional climate. Among the morphometric characteristics of the relief, altitude plays the most important role in the spatial conditioning of the analyzed parameters. The spatial distribution of evaporation and evapotranspiration, at annual, seasonal and monthly levels in Romania was made through the spatial interpolation method (Digital Terrain Model with a resolution of 30 m). The results of the analysis revealed the following aspects: on a multi-year period, evaporation in Romania ranges from 300 mm – 800 mm/year, with the highest values recorded in the south east of the country and the Danube Floodplain (over 1,000 mm/year), western part (over 800 mm/year) and the lowest values registered in the mountain areas (less than 400 mm/year). The values of evapotranspiration vary between 300 mm/year and 625 mm/year, with a maximum of over 650 m/year in the plains and a minimum of less than 300 mm/year in the mountains.

Volume XV |

Assessment of Flash Flood Hazard Maps Using Different Threshold Values and Indices Methods

Abstract: This paper presents an integrated approach for preparation of flash flood hazard maps using different threshold values and indices methods. The methods are based on the influence of the main physical-geographical factors on the rainfall-runoff processes.
The approach utilizes the ROFFG threshold runoff values for the small sub-basins configured within the Romanian Flash Flood Guidance System (ROFFG), together with robust runoff coefficient estimates for selected rainfall scenarios. Calculation of Flash Flood Potential employs a dimensionless index based on several geographical factors determined in GIS (raster format at 30 meters cell size) that influence the surface runoff. The index and general rainfall-runoff analysis in representative gauged sub-basins (area < 200 km2) are used for the general validation of the results of the ROFFG threshold runoff method. The results of the ROFFG method highlight the existence of a high hazard caused by flash floods in 2401 basins, which cover about 61754 km2 (25% of the total area of Romania). The Flash Flood Potential Index (FFPI) method highlights too high and very high values of FFPI in 2805 small basins covering an area of about 80000 km2 (approximately 33% of the total area of Romanian area). Both methods indicate that the highest flash floods hazards occur in the mountain and hilly areas.

Volume XV |

Results of a long-term study on an experimental watershed in southern Italy

Abstract: Forested watersheds offer a wide array of benefits. In fact, forest cover affects the hydrological response of a basin, regulating the volumes of water content in the soil through processes of interception, infiltration, and evapotranspiration. Altering forest cover can significantly influence water balances at both site and watershed scale. Understanding the relationship between vegetation and streamflow is vital to assess the effects of forest disturbance on hydrologic response, and to identify best management practices in a watershed. The aim of the present research was to evaluate the role of forests in the hydrological processes which occur in a headwater basin draining a Calabrian pine forest (Pinus laricio Poiret). Moreover, the analysis also involved studies of forest carbon uptake. Since 1986 the Bonis watershed has been instrumented and precipitation, runoff, throughfall, stemflow, and some climatic parameters have been measured. Recently, in order to study carbon and water cycle dynamics (for climate change mitigation assessment) and to give information about the amount of water used by plants, a tower with Eddy covariance technique was installed. The study concerned the analysis of precipitation and the interaction between forest cover and throughfall, stemflow and runoff after a thinning treatment. Investigation on CO2 and evapotranspiration with the Eddy covariance methodology has also been performed. Results have shown an increase (more than 50%) of the runoff in the basin after the forest thinning (50% of the stems corresponding to 30% of the basal area) while no significant differences in rainfall have been detected before and after the forest thinning. In particular, after the thinning, the runoff coefficient increased from 0.21 to 0.29 during the autumn-winter period, while in the summer season it shifted from 0.16 to 0.41. The results of this study evidenced the effect of a silvicultural practice on the runoff response thus showing that an appropriate forest management can have a key role in water management at basin scale.

Volume XV |

Measuring and modelling water transport on Skaftafellsheiði, Iceland

Abstract: Areas with thick basaltic aquifers are used for drinking water supply and irrigation purposes, such as the Columbia River Basalt group in northwest USA and the Deccan Traps in India. However, rainfall-runoff processes in these basaltic areas are poorly understood. Cooling joints can transport large amounts of water, but – due to their limited porosity – they are vulnerable for over-abstraction. On Iceland, in the small Skaftafellsheiði basaltic catchment (4 x 6 km), field data were collected in 2014 and 2015. Two small streams discharge the rain surplus. Precipitation was measured at various elevations on the ridge. Also, the discharge of the streams was measured. A groundwater flow model was constructed in order to get more insight in the physical properties of the basalt aquifer and its rainfall-runoff properties. The field experiments showed that precipitation increases linearly with surface elevation. On average, the precipitation at 800 m+msl was almost double, relative to the precipitation at 200 m+msl. Calculated ETpot was rather high, due to the 19 potential sun hours per day during the Icelandic summer. Field experiments revealed quick discharge response on rainfall events, but also rather constant base flow during dryer periods. This indicates a limited infiltration capacity, but also a considerable storage capacity in the subsequent layers. The peat layer is believed to be the dominant storage/reservoir. Peat, regolith and an organic layer formed the top layer in the GMS-Modflow groundwater model. The thick basaltic aquifer was split in a series of model layers. Best results were obtained by using a decreasing hydraulic conductivity to depth. The transient model overestimated the groundwater levels at the outlet, but managed to reproduce the wet/dry conditions in the catchment rather well. This indicates that it is possible to model complex basaltic aquifers, by taking a large Representative Elementary Volume (REV) as starting point.

Volume XV |

Smart Data for ICT-based Water Management

Abstract: Water is an essential, limited and sensitive life resource, and it is in focus of various persons or groups, from simple citizens to decision persons at country/world level, and, of course, also of scientists from different research fields. Water resource dynamic consequences exceed watersheds or water systems. Due to the support of new technologies, researches like people, water, and climate: adaptation and resilience in agricultural watersheds, developed a better understanding of the processes that link global-scale climate and socioeconomic drivers to regional-scale responses in land use decision-making, water quality, and water quantity. Recently, Cloud Computing emerged as the de facto state-of-the-art for data analytics. We require optimized platforms to co-locate data and computation and therefore mitigate the network bottleneck when moving data. However, as data may not be equally distributed across sites and since intermediate data are required to be aggregated to produce results, Cloud computing platforms may suffer severe performance degradation in such distributed settings. Thus, in our research activities we intend to address smart data extraction for water resource management, to explore new data distribution techniques and decision support systems that can co-operatively deal with distributed big data processing for single and multiple concurrent applications. Another challenging issue is to provide real-time analysis of shared and distributed data. While most real-time processing engines can efficiently benefit of the un-debatable performance of in-memory processing, they don’t consider the data management during data processing (i.e. where to store the intermediate temporary data) or dependencies in-between processed data, which are common in environmental applications. In this case, mathematical models represent suitable instruments used in prediction and prognosis model for different parameters (i.e. water quality index), which are important for decision support systems for water resource management.