The Aksu (Bronze Age name in Hittite: 𒁉𒋻𒀀𒅀, Kaštaraya, ancient name in Greek Κέστρoς, Kestros), is a river in Antalya Province (southwestern Turkey), which rises in the mountains of Toros. The course of the Aksu is between the Düden to the west and of the Köprüçay to the east. It discharges into the Mediterranean near the city of Antalya. The river is about 145 km long and has a total catchment area of 3652 km². There are several lakes in its catchment area, including Lake Kovada and the reservoirs created by the Karacaören-1 and Karacaören-2 Dams. The Aksu is primarily fed by karstic springs in the Taurus Mountains. In contrast to the many seasonal streams in the region, the Aksu flows year-round, although its volume can fluctuate dramatically throughout the year. For example, its flow was measured in 1942 to be 250 m/s³ in January and 7.5 m/s³ during the summer. Like other karstic streams, the Aksu does not carry much sediment with it. In its lower reaches, the Aksu forms a soft, fertile alluvial plain, which contrasts sharply with both the hard travertine complex around Antalya to the west and the rocky Pleistocene terraces to the east. The Aksu's delta is wave-dominated, due to the river's low sediment load and strong coastal currents. These processes have turned some former river mouths into closed-off limans and created four distinct systems of dunes running parallel to the coast, reaching heights of up to 12 m. Some parts of the delta, particularly around river mouths, are swamps which were historically sources of malaria. Today, the river is impacted by human activities. The Karacaören-1 dam was built to provide water for irrigation, produce electricity, and control flooding downstream. The Karacaören-2 dam was built to provide drinking water for residents of Antalya. The dams siphon off a lot of the Aksu's water to generate electricity, and intensive agriculture in the areas downstream also uses up a lot of the water. As a result, the lower Aksu carries much less water and may even run dry sometimes. The river is also impacted by pollution at several areas: the dam reservoirs are used for domestic and industrial wastewater discharge, and a water treatment plant also discharges into the Aksu. History A treaty between the Hittite Great King Tudhaliya IV and his vassal, the king of Tarhuntassa, defined the latter's western border at the "Kastaraya River", near