BBC News
By Craig Duggan
image captionHydro schemes harness the power of water as it flows through a turbine to generate electricity
Private hydropower schemes are "on a cliff edge" in Wales due to a decision to withdraw business rate relief for some projects from April, according to the British Hydropower Association.
In Wales, it is estimated it would cost less than £500,000 a year.
The Welsh government said over half of Wales' energy needs were met through renewable sources.
It said this included a 2% contribution from 363 hydropower projects, and it had "no evidence of any projects ceasing to operate due to unsustainable costs".