Author(s): Stella Volpini; Marco Pilotti; Giulia Valerio

Linked Author(s): Stella Volpini, Marco Pilotti, Giulia Valerio

Keywords: Wetland; Torbiere d’Iseo; Wind; Temperature; Water circulation

Abstract: The Natural Reserve “Torbiere del Sebino” is situated on the southern bank of Lake Iseo and is one the most important wetland for extension and ecological importance of northern Italy, belonging to the Natura2000 network. Torbiere occupies an area of 360 hectares and almost 12000 inhabitants live in the drained watershed, where most of the land is occupied by wineries; this leads to a significant anthropic pressure that has compromised the system and changed the equilibria between species. Despite the ecological relevance of the area, very little quantitative information is available regarding its current state and evolution in terms of hydrodynamics and water quality. Given the critical environmental condition of the habitat, it is necessary to address the extent of human impact on the trophic state of Torbiere. As a first step in this direction, a three-dimensional model was set up to study the thermal and hydrodynamic response of the system under the action of radiation, wind and inflows. The latter consist in the main affluent entering from the South, and a secondary affluent from a sewer overflow of Provaglio municipality that provides an occasional but volumetrically relevant contribution to the wetland mass balance. In both these sites, we used a water level gauge to provide an estimation of the incoming discharges. The radiative data were obtained by the data measured by a weather station located in Iseo. The temperature field provided by the model was compared with the data available in the wetland, consisting in several vertical profiles measured in different wetland locations in different seasons, as well as an high resolution temporal series measured continuously by a fixed probe. The calibrated model was thus used to investigate the effects of the wetland morphometry on the water circulation. In the reserve there used to be a complex connection system with banks forming a set of separated tanks. This system was deeply modified several decades ago because it was considered to have a negative effect on the water quality of Torbiere, hindering water circulation and creating stagnant zones. For this reason, parts of the banks were demolished towards the end of last century, to create channels connecting the small shallow lakes. A comparison between the circulation in the two configurations allowed to clarify the actual effectiveness of intervention.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022456

Year: 2022