Accumulation of water and sediments upstream of Tuscan check dams

Faced with a decline in water resources due to precipitation reduction and variability, it is fundamental to identify potential natural "reservoirs" and quantify their water retention capacity. This study examined approaches to estimate the water content rapidly and systematically in the sediment upstream of check dams at different scales, even with limited input data. The study was conducted in the northern part of Tuscany, with a specific focus on the Casentino Valley. After gathering the necessary databases and information, an estimation model was developed using QGIS Model Designer, and geophysical surveys were performed using Electrical Resistivity Tomography (ERT). The QGIS-based model relies on limited input data, including the geographical positioning of weirs, the hydrographic network, and a Digital Terrain Model (DTM) of the study area. This method provides useful initial approximate estimates of the water resources in the study area. The ERT surveys revealed varying patterns depending on the lithology of different areas, but a clear discontinuity between the sediment wedge and the original riverbed was observed, confirming the effectiveness of this tool in analyzing each individual structure. With the data obtained through the databases, it was also possible to conduct an analysis on the relationship between the original slope and the compensation slope of sediment wedges, and the distance between check dams located on the same river reach. In the perspective of utilizing these natural reservoirs, possible maintenance interventions are proposed, especially on the existing spillways, to make a portion of the available water usable, accompanied by an assessment of potential implications. In the future, implementing the outlined procedures and integrating them with other tools could provide support for evaluating and utilizing these "hidden water resources."