Abstract
For Europe, a reduction of 80% of the potential storage volume due to reservoir sedimentation is predicted by 2080. Sedimentation processes trigger the decrease of the storage volume and a related restriction in hydropower production. Further, the artificial downstream flushing of deposited fines has manifold effects on the aquatic ecology, including changes in morphology and sediment quality, as well as increased turbidity and subsequent stress for aquatic species. However, it is common to lower the water surface of reservoirs for technical inspections, which is not comparable to reservoir flushing operations. The presented case study deals with such a controlled drawdown beyond the operational level of the Gepatsch reservoir (Tyrol, Austria). Based on the awareness of possible ecological consequences, an advanced set of measures and an integrative monitoring design, consisting of a detailed event-based quantification of suspended sediments, changes in the morphology, especially with respect to fine sediments, and analyses of the biological quality element fish on the reach scale along the Inn River have been developed.
Highlights
The sedimentation of reservoirs causes diverse problems from an operational perspective
The controlled drawdown can be divided into two characteristic periods: (i) the drawdown itself from 07 December, 2015 to 13 January, 2016 and (ii) a cleaning phase from 14.01.2016 to 14.03.2016
It can be concluded that the reach scale monitoring data and especially the reach scale assessment were useful for determining the possible impacts of increased fine sediment loads on the aquatic biota
Summary
The sedimentation of reservoirs causes diverse problems from an operational perspective. This is one of the most significant global issues concerning the future use and development of hydropower [1] as well as in water engineering in general. A few decades ago, the basic question of the lifetime of artificial reservoirs was hardly addressed by sedimentologists and hydraulic engineers [2]. As result of this omission, the sedimentation of reservoirs has become a global challenge.
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