The Shannon River drains a forested catchment in the 1000-1400 millimetres rainfall zone. After flowing through steep valleys in its upper reaches, the river crosses a wide swampy coastal plain before flowing into Broke Inlet. The river water is both fresh and low in nutrients and sediments. The entire catchment is contained within the Shannon and D'Entrecasteaux National Parks.

The Shannon River has been classified as a Wild River by the Australian Heritage Commission.

The five sites were sampled in November 2007.

The commonest fish species found in the River was the Western Minnow, Night Fish and the Western Pygmy Perch, which were found at every site. The Balston's Pygmy Perch was found at SHA05 and SHA06. Marron and freshwater crayfish species Cherax crassimanus were also found in the catchment. Tadpoles were only recorded at site SHA01. Pictures of these can be viewed in the gallery.

The Shannon River is in pristine condition with every site determined to be in A grade condition.

Water samples were taken once from each site so while they help describe the water quality at the time of sampling they can not be used to explain the overall condition of the river for the rest of the time.

The Shannon River is a fresh water system with an average conductivity reading of 0.3mS/cm.

The River is acidic with all sites recording a pH less than 6.5 (7.0 pH is neutral). The level of pH ranged between 4.98 - 6.1.

The level of turbidity at most of the sites was low with the level of turbidity ranging at these sites ranging between 1.0 and 0.0NTU. SHA01 recorded a high level of turbidity at 12.7NTU.

All sites, apart from SHA01, recorded a low level of total phosphorus with levels ranging between 14 - 17μg/L. SHA01 recorded a moderate level of 43μg/L.

All sites, apart from one, recorded low levels of total nitrogen. The levels ranged between 720 - 760μg/L. Only SHA01 recorded a high level of total nitrogen.