ISSUE 6
OCT-DEC 2004

Storage reservoirs

In recent studies undertaken, two separate proposals have been made for the construction of storage reservoirs; the first was for the construction of a dam at Kavouropotamos river, and the second the construction of an interception dam at Vrontas river.

The Kavouropotamos river is located in the southern part of the island. The water of the proposed dam, with a capacity of 450,000 m³ (dead volume equal to 30,000 m³), would be intended for domestic supply only, and a drinking water treatment plant of capacity 7,500 m³/d would be necessary. Extensive distribution networks to supply the entire island have been proposed by the study. The cost specifications of the dam and related waterworks are presented in Table 1.

The construction of an interception dam at Vrontas river, which is located in the eastern part of the island, would contribute to the enhancement of local aquifers and therefore enhance domestic and irrigation supplies while inhibiting sea water intrusion. The specifications of the dam were:

Capacity: 98,000 m³,
Dead volume: 30,000 m³,
Construction cost: 1.1 million €.

Construction for both dams starts in 2005 and it is estimated that they will be fully operational in 2009. In the scenario that was examined, Kavouropotamos dam was connected to the areas of Agairia, Marpissa and Paroikia, since the perimetric connection that was proposed is considered too costly and high energy heads are required to transfer water up to the northern settlement of Naoussa. Estimated runoff for both dams is presented in the Annex.

Table 1. Cost components for Kavouropotamos dam

Cost Component	Cost (million €)
Dam	4.70
Drinking water treatment plant	0.01
Connections
From DWTP to Syrigos (Agairia)	1.42
From Syrigos to Paroikia	1.18
From Paroikia to Naoussa	0.72
From Naoussa to Marpissa	1.11
From Marpissa to Dam	0.96
Total	9.13

Option results

Figure 1 presents the abstraction from Kavouropotamos dam and the groundwater recharge from Vrontas dam under the BAU + Normal scenario.

Figure 1. Monthly abstractions from Kavouropotamos and Vrontas dams for the three scenarios (year 2009)

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Effectiveness

The construction of storage reservoirs can be an effective solution in meeting domestic needs while at the same time increasing irrigation demand coverage, as can be seen in Figures 2 to 5. Under normal (average) availability (BAU+Normal scenario), the effect of the option is similar to the one of desalination. However, the option performs much worse in the case of dry years, when inflows to both dams drop to 30% of normal (average) ones.

Figure 2. Percent demand coverage effectiveness of Storage Reservoirs to Domestic use

Figure 3. Percent Improvement of deficit in Domestic use with respect to the reference scenarios

Figure 4. Percent demand coverage effectiveness of Storage reservoirs to Irrigation use

Figure 5. Percent Improvement of deficit in Irrigation use with respect to the reference scenarios

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Direct and Environmental Costs

Since alternative financing schemes are not examined at this stage, the Kavouropotamos dam is considered to be too expensive (even without including the operational costs of the system, such as pumping requirements). Another disadvantage concerns the operation of such an extensive network rather vulnerable to failures, which also renders the construction of a remote monitoring system for leakage control, and the facilities to support this, necessary. At the same time, the interception dam at Vrontas can with significantly lower costs help in the mitigation of the overexploitation of the aquifer and assist in sustaining the irrigation of the traditional vineyards in the municipal department of Naoussa.

Figure 6. Total direct cost difference of the Storage reservoirs option
under the three scenarios (Present Value – Million €)

Given that the levels of abstraction are reduced and the recharge is increased due to the introduction of the interception dam, the environmental costs show a perceptible reduction, which becomes significant under the LD+HW conditions, which are optimal for both storage and groundwater recharge (Figure 7).

Figure 7. Total environmental cost difference of the Storage reservoirs option
under the three scenarios (Present Value – Million €)

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