Seite - 606 - in Book of Full Papers - Symposium Hydro Engineering

A USEFUL TECHNOLOGY TO SOLVE OR MITIGATE ARTIFICIAL RESERVOIR SEDIMENTATION Francesco GALANTE Hydraulic Consultant of DRAGFLOW Luca MASOTTI Sales Manager of DRAGFLOW Claudio FORNASARI Managing Director of THETIS COSTRUZIONI ITALY KEYWORDS: dam operation, flood storage, grain size distribution, res- ervoir operation, settlement, siltation; MOTS CLE: exploitation, réserve de crue, granulométrie, exploitation du reservoir, tassement, alluvionnement 1. RATIONALE Reduction of sediment flow generated by dam construction leads to erosion on downstream riverbed and on coastal areas; the lack of coarse sediment (sand, gravel) generated channel riverbed deepening and relevant effects on bridge foundation structures, and on other infrastructure affected by water bodies, meanwhile the lack of fine sediment (silt, clay, nutrients) can have serious effects on balance of downstream ecosystems, reducing water turbidity and affecting water temperature. Loss of reservoir capacity caused by sedimentation can greatly impact reservoir management because it generates a reduction of water availability for several uses (energy generation, irrigation, drinking water). Most recent studies estimated global gross storage capacity at 6,000 km3 and annual reservoir sedimentation rates at 31 km3. According to this growing trend, global reservoir storage capacity will be reduced by 50% on 2100. Both accumulation of sediments in dams and the lack of these in down- stream areas have negative effects on the performance and conditions of the infrastructures, on the coastline stability, already endangered by sea level rise (greenhouse effect), therefore actual handling of these sediments is of paramount importance for long term management of artificial reservoirs. 606