Dams, or reservoirs, have as their main objective the storage of storm water for use by mankind (power generation, irrigation, water supply, flood control etc).  Cyprus has been always facing water shortage problem.  In order to mitigate this problem the policy “Not a drop of water to be lost at sea” was adopted.  As a result of this policy almost all main rivers of the island have been dammed.

The arrest of sediments in the reservoirs is an indirect impact of the water storage due to the transport of sediments by the surface water flow.   The trapping of sediments in the reservoirs:

• Reduces the storage capacity of the project
• Arrests the sediment supply to the river mouth/ delta which results in the recess of the delta and the erosion of the coastline in the coastal system associated with this delta.

The dams of Cyprus have succeeded in the mitigation of the water problem of the island but they have caused the arrest of the evolution of the deltas and the erosion of beaches.  For the achievement of sustainable management of sediments in the presence of reservoirs it is necessary to develop a new method for the acquisition of sediments trapped in reservoirs and their transportation to their natural destination, the mouth of the dammed river.

In parallel and independently from the sediment management, it is necessary to ensure that the quality of the water entering the reservoir is acceptable.  Fires, accidents, effluents of fertilizers, chemicals etc might pollute the water stored in the reservoir.

A new proposal has been developed in this research program which addresses holistically the problems of sediment management and water quality.  This proposal is, in summary, a small dam, called pre-reservoir with the following characteristics:

• It is constructed in the entrance of the existing dam reservoir (no land reclamation is necessary)
• Storm water is temporarily stored
• The water quality is checked after the storm:
• If the quality is acceptable, then the water is allowed to enter the reservoir through a pipeline
•  Ιf it is not acceptable, then the appropriate measures are taken (e.g. collection and treatment, diversion downstream)
• The sediments are collected and their quality is tested:
• If their quality is acceptable, sieving takes place and suitable material is transported and deposited at the river mouth/ beach.
• If their quality is not acceptable, then suitable measures are taken (e.g. treatment, burial etc).

The cost of this proposal is very low compared to the benefit achieved.  In particular, the design of a pre-reservoir as a pilot project for the Evretou Dam was carried out.

• The initial/ capital cost is estimated to be of the order of 450 000 Euros (very small percentage of the cost of the dam)
• The annual cost of evacuating the sediment is 5 Euros /m3 (small amount compared to the evacuation using dredging)
• The annual cost of selection of sediments and stransportation to the beach is 10 Euros /m3 (reasonable cost/ no alternative source)
• The cost of mitigating of accidents depends on the pollutants

At policy level it is proposed:

• to replace the existing policy of “No drop of water to be lost at sea” with

“No drop of water to be lost”

• to adopt the policy of taking measures to:

Ensure that water of acceptable quality enters the reservoirs

Collect, select and transport suitable sediments from the reservoirs to the beach

Maintain the storage capacity of the reservoirs.