The project on “Escalating Small Hydropower Development and Aquatic Biodiversity of Mountain Streams in Sri Lanka” is to build up the awareness of different categories of stakeholders in small hydropower generation sector, namely, small hydropower developers, consultants to developers, environmental officers, and relevant policymakers levels on the importance of correct design and operation of environmentally sustainable small hydro power plants. It also anticipated convey the message regionally and globally. The critical impacts of poorly designed small hydro power plants are very diverse; primarily affect on aquatic biota in terms of population decline and eventual species extinction including endemics. In Sri Lanka, about 600 stream sites have been identified as potential sites and 128 plants have already been in operation. Preliminary studies showed that 1-2 km stream stretch had been affected at each small hydropower plant. And most cases, the developers do not maintain the ecological flow, which is a requirement. The negligence of the developers and poor understanding of the relevant authorities have led a devastating damage to mountain stream ecosystems in terms of aquatic biodiversity. Therefore, it is imperative to emphasize the issue to the relevant sectors while enhancing capacities of stakeholders of different levels to achieve the development goals in a sustainable manner.