Restoration of the Soltarico oxbow Lake

PROJECT DESCRIPTION

BACKGROUND

The Soltarico oxbow natural reserve, proposed as a Site of Community Interest, was created when the river Adda flooded in 1976. It is the largest oxbow lake in Italy. The area is an important feeding ground for nesting herons in the middle stretch of the Adda. In the absence of suitable nearby wetlands, such as the ricefields to which most of the Po basin heron communities are connected, the Soltarico oxbow has strategic value for the protection of local heron populations. The oxbow is characterised by a widespread cover of water plants, including nymphaea alba and nuphar luteum, while along the banks are hygrophilous forests of alder and willow. There are also strips of mesophilous oakwood dominated by common oak, elm and poplar. As the oxbow lake has been cut off from the main river channel, the area is currently threatened by phenomena such as silting and anoxia. These phenomena, together with the deterioration of the natural woods and the expansion of intensive farming, have altered the original ecosystem and harmed existing ecological balances. Accordingly, the project aims to restore a large part of the area by reconnecting the lake to the river Adda to encourage hydrological exchange by reconstituting the primary riverine forests.

OBJECTIVES

The purpose of the project was to upgrade part of the Soltarico oxbow lake by restoring the inflow and outflow of water and renaturalising hygrophilous communities and stretches of riverine hygrophilous forest. The removal of sediment in the riverbed, where it impedes sufficient water flow, and the remodeling of the banks were planned. This restoration work was intended to reestablish the former hydrological balance of the river, to reduce the anoxia process and to increase the biodiversity of the wetlands. In addition, measures to renaturalise the primary riverine vegetation were to be carried out through reafforestation with native species and elimination of invasive species in order to reestablish the structure and composition of flora of the hygrophilous forest stands.

RESULTS

The project achieved only a very small part of its foreseen objectives. In fact, the beneficiary realised that the key measure, i.e. the reconnection of the oxbow with the main stream of the river Adda, was technically not possible. Only two field measures were successfully completed:

removal of the false indaco amorpha fruticosa, with a positive impact for the potential recovery of the priority habitat *91E0 “Alluvial forests with Alnus glutinosa and fraxinus excelsior (alno-Padion, alnion incanae, salicion albae)”,

creation/restoration of four pools would benefit amphibians recorded in the SCI where the project took place, like rana latastei(annex II and IV), hyla intermedia (annex IV, under hyla arborea) and, possibly, *pelobates fuscus insubricus. The beneficiary also carried out studies on flora and fauna. Additionally some dissemination actions were developed, such as publishing a booklet and a video and organising a final meeting.The project achieved only a very small part of its foreseen objectives. In fact, the beneficiary realised that the key measure, i.e. the reconnection of the oxbow with the main stream of the river Adda, was technically not possible. Only two field measures were successfully completed:

removal of the false indaco amorpha fruticosa, with a positive impact for the potential recovery of the priority habitat *91E0 “Alluvial forests with Alnus glutinosa and fraxinus excelsior (alno-Padion, alnion incanae, salicion albae)”,

creation/restoration of four pools would benefit amphibians recorded in the SCI where the project took place, like rana latastei(annex II and IV), hyla intermedia (annex IV, under hyla arborea) and, possibly, *pelobates fuscus insubricus. The beneficiary also carried out studies on flora and fauna. Additionally some dissemination actions were developed, such as publishing a booklet and a video and organising a final meeting.