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Eberstaller, J. and C. Gumpinger (1997). Low-gradient nature-like bypass channel on the river Pielach. Osterreichs Fischerei. 50:47-51.

This low-gradient bypass channel at the "Tessmer-Wehr", on the river Pielach, is the first of its kind (i.e. without vertical drops) in the province of Lower Austria. The authors know of only one other such bypass constructed in Austria, located on the middle portion of the river Salzach. The morphology of the bypass channel resembles a natural, structure-rich tributary of the Pielach and the entrance to the bypass is located immediately beside the weir. Both factors help guarantee permanent passage for all occuring species and their corresponding life history stages. The discharge of the channel corresponds to the natural discharge regime of the Pielach, providing optimal conditions for passage during the spring spawning migrations of the dominant occurring species. Detailed plans of the construction were not made before hand, in order to allow more on-site flexibility whereby trained field consultants supervised the construction crew in creating a highly variable and more nature-like channel. Particulary important in reaching this goal were the fine adjustments made to the channel's structure after the flow inlet was opened and the consultants could observe potential problem areas for passing fish.