Hydroelectric turbine

A method for manufacturing a turbine system comprising:

• forming a central cylinder by polymer fabrication, wherein the central cylinder comprises a curved cylindrical surface, a first end face and a second end face opposite the first end face, wherein the first end face and the second end face are joined by the curved cylindrical surface, and wherein the central cylinder has an inner cavity;
• forming a plurality of helical vanes by polymer fabrication;
• welding the plurality of helical vanes to the outer side of the curved cylindrical surface;
• wherein channels are formed between each of the plurality of helical vanes which allow fish to pass along the channels;
• characterized by:
• forming the maximum radial extension of the first end face and the maximum radial extension of the second end face to be greater than the radius of the curved cylindrical surface;
• and
• forming gaps in the outer circumference of the first end face and the outer circumference of the second end face to be configured to allow, in use, fish in the channels to exit through the gaps.