Visual effects of waterfalls affected by water diversion

摘要

When considering the renewal of a hydropower or other water withdrawal concession, the general benefits of the scheme have to be weighed against its ecological disadvantages. Loss of water from a scenic waterfall will often be considered as a considerable drawback. Also, if granting concession, the licensing authority will limit the minimum release discharge, which may have a considerable impact on project economy. The visual impact of reducing the discharge in a waterfall is significant for the feasibility of hydropower or irrigation projects, but currently no generally accepted guidelines for quantifying the relationship between discharge and visual appearance exist. There is thus a need for a methodology to determine the minimum residual flow of waterfalls. Based on results from a case study covering seven waterfalls in Norway and Austria, such a methodology is presented accounting for the visual effects of flow changes at waterfalls. A guideline for stepwise residual flow determination at waterfalls is given.