HYDROMETEOROLOGICAL MEASUREMENTS IN THE TARO RIVER GIANT ALLUVIAL FAN

In the framework of the National Project: “Esplorazione geofisica e geologica di alcuni complessi acquiferi alluvionali nella pianura Padana tra Milano e Bologna, per la modellazione della circolazione idrica sotterranea”, the soil water content profile in the surface soil is measured at two stations located between the town of Parma and the Taro River (Po valley). The physical structure of the Taro River giant alluvial fan is well known because of the previous studies of the University of Parma geologists involved in the same National Project. On the basis of this knowledge, one station was installed at the site of the well #1 of Roncopascolo and the other at a site closer to the Taro River (Barilla field). At Roncopascolo, meteorological data are also collected, including air temperature and relative humidity at two levels, while, at Barilla field, only the soil moisture profile is measured. The aim is to study the partition of the water entering the surface of the soil in: evaporation, run off, water stored in the measured soil column and percolation towards the deeper layers. The soil water content measurements are performed with Frequency Domain Reflectometry (FDR) sensors; the scaled frequencies and the meteorological data are automatically collected and stored in a data logger and then transmitted when required. Roncopascolo station started at the end of July 2006, while Barilla station started in October 2006. At both stations, soil samples were taken for the laboratory determination of the soil physical characteristics. The time variation of the water stored in the studied soil columns is estimated by means of the mass balance method. From the data collected in the summer period, the evaporation is estimated. Similarly, applying the mass balance method to the data collected during and after heavy precipitation events, the water infiltrated into the soil can be estimated. Furthermore, the time evolution of the soil moisture profile is studied solving the linearized one-dimensional Richards equation for discrete arbitrary initial and boundary conditions. The results are the soil water content at any required time and depth in a semi-infinite unsaturated porous medium domain, the ponding time, the desiccation time and the surface water flux during the soil-controlled phases of infiltration or evaporation.