Tjele Langsø is a deep and nutrient-rich lake that flows into the Hjarbæk Fjord through the Vorning Å and Skals Å. The water temperature during the summer period ranges from about 1 to 22 degrees Celsius.

Tjele Langsø is located in the remains of a long, elongated tunnel valley that originated around the Mariager Fjord. The tunnel valley joins a more northerly tunnel valley around Viborg, from where meltwater streams continued to the Hald Sø area. From there, the water flowed further out over the Karup Hede plain.