Gilbert River, Stockport
2008 Aquatic Ecosystem Condition Report
- Affected by nutrient enrichment and erosion.
- Large growths of algae and aquatic plants.
- Limited riparian zone dominated by introduced plant species.
- Site dry at time of inspection in spring 2008.
About the location
The Gilbert River rises near Manoora in the Mid North of the state. It flows south through agricultural land, used mainly for livestock grazing and cereal cropping, before joining the Light River west of Hamley Bridge. The site selected for monitoring was located off Murray Street in Stockport.
The river was given a Fair rating at this site because the ecosystem had moderate changes to animal and plant life, and some changes to the way the ecosystem functions. Human activity had significantly affected the riparian zone, and several lines of evidence pointed to high nutrient levels.
The downstream site at Stockport was dry when inspected in spring 2008. However, aquatic plants such as Common Reed (Phragmites australis) and sedge (Bolboschoenus caldwellii) were growing over much of the channel. Dried green filamentous algae (Cladophora) covered most dry sediments throughout the site. Several terrestrial plants such as saltbush (Atriplex) and introduced ryegrass were also growing in the channel, highlighting a lack of water in recent years.
The sediments were mainly grey sand and silt, which were most likely anaerobic, or lacking in oxygen, when wet. The channel was heavily eroded from flooding after heavy rain; livestock accessing parts of the stream on occasion may have been another contributing factor.
A narrow strip of introduced pepper trees, shrubs and grasses formed a limited riparian zone along the riverbanks. The surrounding area was covered mainly with gardens in the township area, and cereal crops.
Special environmental features
Pressures and management responses
|Livestock have direct access at the site and upstream, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||
The Northern and Yorke Regional NRM Plan has the following Resource Condition Targets:
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).|
|Saline groundwater inflow (reducing ecological integrity).|