About Yliki Dam

Yliki is a naturally occurring lake that was enlarged to serve as a major water storage reservoir, situated in Boeotia in central Greece between the Helicon and Cithaeron mountain ranges. With a capacity of 600 million cubic metres, Yliki is the second-largest water source in the greater Athens region after Mornos. Like Mornos, water from Yliki reaches Athens through the same Mornos-Athens Aqueduct, feeding into the same integrated water transfer network that supplies Attica. The transformation of the natural Yliki lake into a managed reservoir reflects the broader Greek water engineering efforts of the late twentieth century — enhancing natural features to serve modern metropolitan demand. The water body has historical significance stretching back to antiquity: the ancient Greeks knew the lake as one of the major water sources of Boeotia, and it features in classical texts alongside references to the neighbouring Lake Copais. The Yliki catchment drains portions of the Helicon and Cithaeron massifs, receiving winter rainfall from the same synoptic weather patterns that feed Mornos. During wet years, Yliki contributes substantially to Athens's total supply, allowing water managers to reduce the drawdown pressure on Mornos. Conversely, during extended drought periods, Yliki's level can fall sharply, and the two reservoirs function as interdependent elements of a single supply system. The lake's surroundings — the Boeotian plateau with its ancient cities, vineyards, and agricultural land — reflect thousands of years of human settlement. Yliki's ecological role includes supporting fish populations and waterfowl, and the lake has attracted modest tourism interest. As drought pressures intensify across Greece, Yliki's supplementary role in the Athens water system becomes increasingly valued by water resource planners.