At the 28th and 30th kilometre markers (17 and 19 miles) of the old route from Antalya-Burdur (which goes through Döşemealtı town), two big karstic sources appear. These sources, Kırkgözler and Pınarbaşı, merge after a short flow and disappear into Bıyıklı Sinkhole. Some of the sinkholes can swallow a river or lake. In this region, the Suğla (Konya) big sinkhole and the Bıyıklı sinkhole output 30 cubic metres per second (1,100 cu ft/s). This quantity is the output of Kırkgöz and Pınarbaşı springs at inundation.
The water, which disappears at Bıyıklı Sinkhole, travels 14 km (9 mi) underground and comes out again at Varsak pit. After a very short fall, it disappears again from the other end. The water which disappears at Varsak goes underground for 2 km (1.2 mi) and comes out again at Düdenbasi, by pressure made by a syphon. The water which falls from Düdenbasi is the water coming from Kepez Hydroelectrical Complex.
A regulator built in front of the Bıyıklı Sinkhole directs the waters of Kırkgözler and Pınarbaşı into a canal to the Kepez Hydroelectric Plant, where a pressure pipe carries it to a balancing funnel and drops it over the plant's turbines....