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Università degli Studi di Cagliari (2020)

Groundwater resource management : methodological approaches and analysis of space-time data useful for assessing environmental impacts in drought contexts (area of Tuscany considered semi-arid)

ZIRULIA, ANDREA

Titre : Groundwater resource management : methodological approaches and analysis of space-time data useful for assessing environmental impacts in drought contexts (area of Tuscany considered semi-arid)

Auteur : ZIRULIA, ANDREA

Université de soutenance : Università degli Studi di Cagliari

Grade : PHD DEGREE SCIENZE E TECNOLOGIE DELLA TERRA E DELL’AMBIENTE (2020)

Résumé
European Water Framework Directive (2000/60/EC) regards underground water resource protection and one of its main challenges is to provide a quantitative and qualitative monitoring activities in order to achieve a "good" status of groundwater resources. A good environmental status of the groundwater resource is linked to its chemical conditions and to its quantitative state, which depends on the equilibrium between withdrawals in the medium-long term and natural recharge. The main objective of this research was to use alternative and non-conventional methods of analysis useful for groundwater resources management and sustainable procurement in environments characterized by dry events and water deficit, paying particular attention to the evaluation of the natural groundwater recharge sources. The specific objective of this thesis was defining the episodes of natural recharge in a porous aquifer located in an area of Tuscany considered semi-arid and characterized by dry events. In order to do this, hydrological and hydrogeological assessments based on automated methods, such as the recession curves MRC (Master Recession Curve) were used. These methods represent the relationship between the value of a hydrograph response and its rate of change over time (dR/dt) at a time when there is no infiltration or other entry of water. The MRC calculated for the time series of the response variable (i.e. the groundwater level) also allowed to determine the recharge episodes through the EMR Episodic Master Recession method. The EMR method is based on the level fluctuation algorithm (Water Table Fluctuation-WTF) and is suitable for identifying discrete recharging episodes from the hydrograph, the recharge amounts attributable to each episode and the amount of precipitation that caused this answer. This method considers a recharge flow in a saturated zone, that causes an increase of groundwater level before that dissipation processes that take place in the saturated zone bring it back to its steady state. This phenomenon is the product of the Specific yield (Sy) of the aquifer and the groundwater table level change (H = H/dt) attributable to recharge. The main challenge of the WTF method is to estimate Sy in groundwater zone fluctuation. Thanks to field measurements obtained with geophysical methods, the actual Sy parameter value was obtained. The integration of utilizes procedures and techniques was useful not only for evaluating recharge episodes, but also for assessing the relationship between recharge events and possible climate changes taking place in the study area. Thus, this research was able to link climatic changes with the modifications in the water level of the studied aquifer.

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Page publiée le 7 mai 2020