Changes in the Coastline and Water Level of the Akşehir and Eber Lakes Between 1975 and 2009

Abstract

The Aksehir and Eber Lakes, relatively shallow, small freshwater lakes with an area of 361 km2 and 150 km2 and average depth of 7 m and 2 m (1998), respectively in southwestern Turkey, have experienced a severe decline in water levels in recent decades. This study aimed to investigate coastline and water level changes of lakes and identify the causes for the decline in lake levels. Nine Landsat images from different times, monthly temperature, precipitation, discharge, lake level records and population data were used to analyze these changes. From 1975 to 2009, the water surface areas of the Aksehir and Eber Lakes decreased from 356,929 to 126,482 km2 and from 119,882 to 85,663 km2, a loss of 64.5% and 28.4% over the 34-year period, respectively. From 1975 to 2004, the Aksehir Lake level declined by 2.67 m from 956.02 m to 953.35 and the Eber Lake level declined by 2.03 m from 966.75 m to 964.72 m from 1975 to 2004 based on ground lake level data (in situ). The results of the temperature and precipitation analysis showed that although the annual mean climatic factors vary substantially, they show small increasing trend over the record periods. Annual discharge records on the Akarcay River and its tributaries decreased over the basin during the same period. Irrigation systems, three dams and seven pounds built in recent decades for agricultural irrigation and domestic use, made the major impact on lowering the lake levels because they derive water from the river for human use upstream of the lakes’ catchments. Population growth, rising water consumption for agricultural and domestic purposes and building dams has led to lake levels declining. The change of lake levels might depend more on anthropogenic factors than on climatic factors.