A combination of time, water and rocks has created the phenomenon of draining, which keeps the life on this marvellous karst plain in motion. Lake Cerknica is intermittent because it fills up after long precipitation periods and drains out during the dry season.
The lake spreads over the Cerknica plain when its water inflow exceeds the outflow. It is filled up in two or three days by heavy autumn rain, whereas in springtime the inflow is affected also by melting snow. Water flows to Lake Cerknica underground from the Bloke and Vid plateaus, the Lož valley and from beneath the Javorniki hills. The only surface tributary is the Cerkniščica stream.
Discharge of water is a slower process. During the dry season, the lake drains out in three to four weeks. All the water seeps underground, making the outflow of Lake Cerknica entirely karstic and the Cerknica plain a typical karst plain.
The underground outflow is complicated. Lake Cerknica acts as a geological watershed from where the water flows in two directions. One part discharges through ponor caves in the Jamski zaliv cove, and surfaces as the Rak river in the picturesque Rakov Škocjan valley. The other part drains through sinkholes and estavelles in the lake basin directly into the springs of the Ljubljanica river on the edge of the Ljubljana Marshes.
|SURFACE OF WATER IN LAKE CERKNICA (HIGH WATER LEVEL):||30 km2|
|Surface of water in Lake Cerknica (normal water level):||20 km2|
Surface of water in Lake Cerknica (LOW water level):
Maximum depth of Lake Cerknica: