Hydrogeological surveys to assess groundwater resources in the middle valley of the Turano River (central Italy)

Abstract

This paper outlines the results of a hydrogeological study conducted in the past decade to quantitatively assess renewable groundwater resources emerging in the middle valley of the Turano River, in terms of recorded average and minimum discharge values. To this end, discharge monitoring surveys were carried out on appropriate sections along the Turano River and on one section along one of its tributaries representing the contribution of the piedmont spring called Laghetto. This spring contributes about 350 L/s on average to the discharge of the river, which acts as a linear spring with an additional average equivalent contribution and represents the local groundwater base level. Based on the geological-structural setting of the area, the basin feeding the spring is supposed to roughly correspond to the Mt. Pelato-Mt. Sole basin and to extend for about 16 km2. The inferred conceptual model shows that the groundwater contained in the Sabine carbonate aquifer: i) supplies both the Laghetto spring and the linear one along the river; ii) also flows in the local aquifer of the Neogene deposits that fill the intramontane basin of Rieti; and iii) has seasonal variability depending on the level reached in the basal carbonate aquifer. The paper proposes a preliminary model of groundwater flow based on quantitative hydrogeology criteria. The model was validated by the calculation of effective infiltration in the spring recharge area, by the physico-chemical parameters of the investigated waters and by isotope data. The correlation of piezometric data with spring elevations indicates that the middle Turano River valley is the zone of discharge of waters that infiltrate into a wide portion of the southern sector of the Rieti basin and which drain towards the plain, travelling in the locally exposed carbonate bedrock. The study thus suggests that the basal aquifer, drained at regional scale by the two large springs of Le Capore to the SW and Peschiera to the E, also has a local point of discharge in the Turano River valley.