River Syfynwy

The river is formed by the confluence of several streams rising in the southern slopes of the Preseli Hills at some 350 metres (1,150 ft) and flows southwards into Rosebush Reservoir, where it passes through or over the dam.

The study, begun in July 2014, is focussed on understanding the blue green algae blooms that have been occurring in the reservoir and, with the support of landowners, will involve soil sampling and nutrient management.

As well as farming, the project will also consider the impact of sewage and forestry on the study area as well as water quality and invertebrate populations.

[9] Over the winter of 2013-14 Pembrokeshire Rivers Trust monitored riverflies at Gelli Bridge as part of a wider study of the Eastern Cleddau catchment area.

[10] A pollution incident in 1999 where trade effluent was discharged into the river causing the death of an estimated 1,000 brown trout[11] resulted in a fine of £2,500 and £13,021 costs when the case went to court the following year.