The silting of reservoirs, resulting from the obstruction of a watercourse’s natural sediment flow, leads to a gradual loss of water capacity in the reservoir. The extent and rate of accumulation depend on the hydrological and geomorphological characteristics of the upstream basin.

Among the techniques often employed by managing entities is flushing, which involves releasing sediment downstream by opening discharge outlets. However, this method has several drawbacks:

• Excessive increase in turbidity downstream of the barrier, significantly impacting ecosystems.
• Limited removal of solid material, primarily confined to the drawdown cone of the discharge outlet.
• Water loss during emptying, leading to a reduction in potential energy production.
• Risks of breakage or malfunction of the discharge outlets.

Mechanical removal of sediments through dredging has been well-established in numerous applications involving dams and reservoirs. Utilizing specialized equipment mounted on pontoons allows for effective interventions, whether targeting specific sediment removal (such as cleaning discharge outlets) or large-scale operations aimed at increasing reservoir capacity.

Dredging with a suction-discharge system, which conveys a mixture of water and sediments through a floating pipeline, offers several advantages:

• Ability to operate at significant depths, exceeding 100 meters.
• Capability to perform in areas with limited accessibility, thanks to modular pontoons assembled on-site.
• Flexibility in choosing various project options regarding the final destination of the removed sediments (e.g., downstream discharge, containment in sedimentation basins, temporary storage, transfer to mechanical treatment plants, dewatering).
• Capacity to discharge over distances of 700–800 meters.

The amount of solid material transported depends on the sediment’s granulometric characteristics, typically ranging from 5–10% for silt-clay materials to approximately 20% for sandy materials.

Thetis Costruzioni possesses the expertise and equipment to effectively operate within reservoirs, even under challenging conditions such as mountainous basins or dredging at considerable depths (over 100 meters).

During dredging operations, to optimize excavation precision and ensure the required levels of suspended solids concentration, excavation profiles are monitored using a profiler system.

This system, specifically developed for precision control in excavation or dredging activities, utilizes software comprising various modules designed for pontoon positioning and high-precision monitoring of excavation depth, with data processing recorded during dredging activities.

A dual-antenna GPS receiver is used to determine the pontoon’s position, providing both location and excavation orientation. The system is optimized by placing the GPS receiver directly on the frame to which the pump’s winch is attached.

The profiler system integrates pre-existing information (maps and bathymetric data) with real-time data from the echo sounder. This information is displayed on a screen in both plan and sectional views. The pontoon profiles are depicted with animated drawings, while the seabed elevations are represented using different colors. The operator can thus visualize in real-time both the planimetric position and the bathymetric elevation of the dredging head relative to the excavation area.

In the plan view, the area’s color changes to reflect the new bathymetry, while in the sectional view, a line represents the path of the dredging head, indicating the new actual bathymetry. This enables the operator to control the dredging depth and be reasonably certain that a specific area has already been dredged.