The Partnach is fed by meltwaters from the Schneeferner glacier some 1,100 m (3,600 ft) higher up.

The glacier's meltwaters seep into the karsty bedrock and reach the surface again near the source of the Partnach.

At the first lake the water of the Partnach was impounded by scree from rock slides.

As a result of heavy rain the natural dam, caused by rockfalls, was partially carried away and the lake was completed filled with sediment.

The Partnach has the following tributaries which join it at or near the river kilometre shown in brackets: