The water level at Sapanca Lake, one of the Marmara Region’s key freshwater sources, has recently dropped to 28.54 meters (93.64 feet), falling below the critical threshold as the region experiences its driest period in the past 65 years.
According to an Anadolu Agency (AA) special report titled “Sapanca Lake Raises Alarm,” the decline is driven by reduced rainfall, rising temperatures, increased evaporation and intensive water use for drinking, industry and agriculture.
Sapanca Lake supplies drinking water to the neighboring provinces of Sakarya and Kocaeli and is fed by streams descending from the mountains to its south, including Karaçay, Kuruçay, Kurtköy, Mahmudiye, Istanbul, Karadere and Kaymakçı. Under normal conditions, the lake’s water level rises during winter and spring and recedes toward autumn.
Since 2023, however, shoreline retreat of 15 to 20 meters has been observed. The volume of water lost over the past two years is equivalent to Sakarya’s annual water consumption, according to experts.
Asude Ateş of Sakarya University’s Faculty of Engineering, Department of Environmental Engineering, told AA that Sapanca Lake is under serious pressure due to climate-related factors and growing demand.
“There is a water budget of approximately 185 hectometers here,” Ateş said. “About 67.5 hectometers are used by Sakarya and 30 hectometers by Kocaeli. In total, nearly 100 hectometers of this budget is allocated to drinking water. When rainfall is insufficient and other water resources are not managed properly, urgent measures are required to protect this ecosystem.”
Ateş also pointed to pollution risks linked to transportation, noting that the D-100 highway runs along the lake’s northern shore, while the TEM motorway and a railway line pass to the south.
Despite the winter season, Ateş said the lake is experiencing severe water withdrawal. She said the critical level for Sapanca Lake is 29.4 meters, adding that authorities aim to keep levels above 30 meters under normal conditions.
“We have just gone through the driest season of the last 65 years,” she said. “Lower rainfall and higher evaporation have brought the lake to this level.”
Ateş said that when water levels reach such critical thresholds, drinking water use should be prioritized, while industrial and tourism-related consumption should be reduced. She also stressed the need to shift agricultural irrigation from flood methods to more efficient systems such as drip irrigation.
She added that snowfall plays a central role in sustaining the lake, as snowmelt feeds water sources over a longer period. Sapanca Lake covers about 47 square kilometers, while its basin spans approximately 300 square kilometers, with groundwater playing a key role in maintaining water levels.
Ateş noted that water consumption has increased in recent years due to the rise in tourism facilities, adding that groundwater use by these facilities still affects the lake’s hydrological system.
She said the lake’s ecosystem requires total water use to remain within 110 to 120 hectometers, warning that allocating nearly all of this volume to drinking water leaves limited capacity for other needs.
To ease pressure on the lake, Ateş pointed to alternative water supply projects, including the Ballıkaya Dam planned by Sakarya Metropolitan Municipality. However, she said it would take at least two years for the project to reduce demand on Sapanca Lake.
“We are at a critical threshold,” Ateş said. “If this level is crossed, lake ecosystems are not easily restored.” She also emphasized that water management must include both institutional measures and responsible individual consumption, noting that water will remain a strategic resource in the coming decades.
