Water Resources Management in Kythira Island (Greece) under High Tourism Pressure and Climate Crisis

Three main aquifer systems have developed on Kythira Island (Greece) (Pagounis, 1981; Pagounis & Gertsos, 1984; Danamos, 1991; Koumantakis et al., 2006; Filis et al., 2019):

• The porous aquifer system within Neogene and Quaternary formations.
• The karst aquifer system developed in the carbonate formations of the Pindos and Tripolitza Units.
• The aquifer system, both shallow and deep, within fractured hard rocks, mainly associated with the Phyllites – Quartzites Unit.

The main discharge of the aquifer systems takes place in coastal and submarine brackish springs around the island, except for its northern part where the Phyllites – Quartzites Unit outcrops and its central part where springs of small capacity discharge the carbonate formations of the Pindos Unit.

Precipitation is the direct recharge of the three aforementioned aquifer systems while indirectly lateral discharge occurs in places between adjacent and tangential aquifer systems and from the streams runoff as well.

The municipal water supply of Kythira has been reinforced by a series of projects and interventions, focusing on the summer touristic period, mainly consisting of new deep boreholes and low-capacity desalination plants.

The climate crisis has led to increasingly frequent high-intensity hydro-meteorological events, particularly in summer, with heavy rainfall over short periods. Consequently:

• Surface runoff dominates, limiting groundwater recharge.
• Evapotranspiration increases due to high temperatures and longer daylight hours.

Taking the above into consideration, the following conclusions can be drawn regarding the water resources of Kythira:

• The coverage of water supply needs during the summer months faces severe challenges, with frequent interruptions in water distribution.
• Overexploitation of available water resources occurs during the summer months, due to the significant increase in population and the inability to meet water demand, as a result of the substantial tourism development in recent years.
• During the period of maximum water demand (summer months), the available water supply is at its minimum.
• The climate crisis has adversely affected the recharge of individual aquifers.
• The drilling of new water-supply boreholes does not always yield the desired results, due to the area’s particular hydrogeological structure.
• Water resources management in Kythira presents a pessimistic outlook, as the projected changes in mean seasonal and average climatic parameters are negative, indicating decreased precipitation accompanied by increased temperatures.

In conclusion, there is an urgent need to implement actions and interventions for the sustainable management of the water resources of Kythira, which, depending on local conditions, may include the following:

• Proposals/measures for the rational management of groundwater resources at the Community level (environmental awareness, drilling of water-supply boreholes, desalination plant locations, protection zones for municipal water abstraction works, etc.).
• Siting of small check dams along watercourses to regulate downstream flow and promote artificial recharge.
• Siting of small reservoirs within and/or outside watercourses for the storage of winter runoff, as well as identification of locations for drilling boreholes for the implementation of artificial recharge, under specific conditions.