Settolo experimental site

Project description

Study area

The study area is located along the left bank of the Piave River, near Valdobbiadene, in the upper Treviso province, and has an extension of approximately 6 km². This is an important recharge area, as the river leaves its mountain catchment and feeds the underlain unconfined aquifer. For this reason, Alto Trevigiano Servizi s.r.l., the agency that manages the water distribution system for most of the Treviso province (49 municipalities, with a population of 310,000 and a water demand of 33,000,000 m³ in the year 2004), has a great interest in the aquifer and has already installed a production well with a maximum capacity of 200 l/s. However, the aquifer is vulnerable to contamination events, due to its large (average) hydraulic conductivity and shallow phreatic surface, hence there is a strong need for a detailed characterization and monitoring of the area.

Fig.1 Settolo experimental site location

Measuring network

The monitoring network includes:

2 hydrometric stations for the measurement of the Piave River water level. The "Piave downstream" is located in the right bank and remotely transmitting data to the Alto Trevigiano Servizi s.r.l. approximatively each 15 minutes. A pressure trasducer and a temperature sensor have been installed in "Piave upstream"station, located in the left bank, with a datalogger recording every 10 minutes
other pressure transducers or multiparametric sensors with dataloggers recording every 10 minutes in 18 observation wells, chosen among the several private wells located in the area or drilled on purpose
3 flowmeters and pressure trasducers for the measurement of pumping rate and water table level at the water distribution agency production well "Base", "Castella" and "San Giacomo", also remotely transmitting data to the agency
A rainfall gauge located at Alano, a town 3 km far from the study area. The gauge records hourly rainfall rates and is remotely controlled by ATS.

The arrrangement of the observation wells in the experimental site complies with a multiple scale approach. The purpose of the monitoring network is to cover two main scales: a larger aquifer-scale, which spans the whole area and a finer local-scale, which focuses on a smaller zone within the catchment where transport processes, vadose zone dynamics, and other local phenomena can be analyzed with improved accuracy.

Fig.2 Big-scale study area

Fig.3 Small-scale study area

Geological surveys

Four core samples were collectedfor stratigraphic analyses. Below a surface loam layer of variable thickness, the data (Fig.4) highlight a stratigraphy composed by layers of sand and gravel of similar granulometry, interspersed with tender conglomerate layers. Grain size analyses conducted in our laboratories classify the main formation as a high permeable sandy gravel.

Fig.4 Core samples whose location is reported in Fig.5
Surface ERT (Electrical Resistivity Tomography) has been carried out along five lines to better characterize the aquifer depth and to point out possible heterogeneities. The results (not shown here) indicate that the range of variation for the aquifer thickness can be estimated from 20 m up to more than 60 m. Moreover, the geology appears to be complicated by the presence of several Piave paleo-riverbeds, which can represent important preferential paths in case of a contamination event.

Fig.5 Position of core samples (C) and geoelectrical tomography lines (G)

Geoelectrical tomographies

Fig.6 Geoelectrical tomography lines whose location is reported in Fig.5