Environmental Effects of Storage Preservation Prac

Authors: Paolo Espa Elena Castelli Giuseppe Crosa Gaetano Gentili

Publish Date: 2013/06/04

Volume: 52, Issue: 1, Pages: 261-276

PDF Link

Abstract

Sediment flushing may be effective in mitigating loss of reservoir storage due to siltation but flushing must be controlled to limit the impact on the downstream environment A reliable prediction of the environmental effects of sediment flushing is hindered by the limited scientific information currently available Consequently there may be some controversy as regards to management decisions planning the work and monitoring strategies This paper summarizes the main results of a monitoring campaign on the stream below a small alpine hydropower reservoir subjected to annual flushing between 2006 and 2009 The removed sediment was essentially silt and the suspended solid concentration SSC of the discharged water was controlled to alleviate downstream impact Control was achieved through hydraulic regulation and mechanical digging alternating daytime sediment evacuation and nocturnal clear water release The four operations lasted about two weeks each and had an average SSC of about 4 g L−1 Maximum values of SSC were generally kept below 10 g L−1 Downstream impact was quantified through sampling of fish fauna brown trout and macroinvertebrate in the final reach of the effluent stream The benthic community was severely impaired by the flushing operations but recovered to preflushing values in a few months As expected the impact on brown trout was heavier on juveniles While data biasing due to fish removal and restocking cannot be ruled out the fish community seems to have reached a state of equilibrium characterized by a lower density than was measured before the flushing operationsThis study was partly sustained by Lombardia Region Agriculture Division under the project “Sediment Removal from Artificial Reservoirs Impact on Fish Fauna and Evaluation of Protection Strategies” promoted by Sondrio Province Environmental Resources Division Field sampling concerning 2009 flushing was partly financed by INTERREG Italy/Switzerland project ECOIDRO Water Use and Safeguard of Environment and Biodiversity in the River Basins of Adda Mera Poschiavino and Inn—ID 7630754 Authors wish to acknowledge eng Ferdinando Bondiolotti eng Sergio de Campo and Mr Bruno Pianta of A2A Work by Francesco Folini Maria Laura Brignoli and Alberto Previde Prato is greatly acknowledged and truly appreciated A heartfelt thank to the three reviewers who provided valuable suggestions for the improvement of the first draft of the manuscript

Keywords: