You may start going through what others are doing; as an example:

Archimedes Screw Generators

http://greenbugenergy.com/how-we-do-it/archimedes-screw-generators

     And also go through literature and images, as follows:

https://www.google.com/search?q=Archimedes+Helix+on+a+River+for+Energy+Production+FROM+A+RIVER+WITH+SMOOTH+FLO&newwindow=1&rlz=1C1AOHY_enIR725IR728&source=lnms&sa=X&ved=0ahUKEwiwzaWggerTAhVpIsAKHW8GANkQ_AUICSgA&biw=1280&bih=709&dpr=1

====

IMAGES: Clicking on each image takes you to so many information:

https://www.google.com/search?q=Archimedes+Helix+on+a+River+for+Energy+Production+FROM+A+RIVER+WITH+SMOOTH+FLO&newwindow=1&rlz=1C1AOHY_enIR725IR728&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjEm5zKgerTAhXPaFAKHZlKB-kQ_AUICigB&biw=1280&bih=709

   That is all I could say and telling the truth, I have never been involved in such a project.

   You may also delve into the new development:

Turbine ​Harvests ​Green Energy Even in Slow ​Water Currents

Waterotor ​Energy ​Technologies ​has designed a ​water turbine ​which can ​harvest energy ​in slow moving ​water. ​

https://thewaternetwork.com/_/energywater-nexus/article-FfV/turbine-harvests-green-energy-even-in-slow-water-currents-zcbAJj_r9LrOUbB_EL2e6Q

Best regards,

Mashallah