Northern and Yorke NRM Regional Summary
2008 Aquatic Ecosystem Condition Report
- High nutrient concentrations, salinity and fine sediments were affecting all streams in the region.
- Impacts of drought a likely contributing factor to the degraded condition of the region’s creeks.
- Decline in macroinvertebrate communities compared with the 1990s, with no rare or sensitive species found at any site.
- Excessive growths of algae and aquatic plants.
- Limited refuge habitats remaining.
- Riparian vegetation very limited with weeds a major issue.
- Cropping to the edge of streams and allowing livestock to access creekbanks contributing to widespread erosion.
Every stream in the region has been significantly altered since European settlement as a result of clearing native vegetation for agriculture. Every site sampled showed evidence of nutrient enrichment such as large algal growths and excessive growths of reeds and other aquatic plants, particularly wherever the stream channel was directly exposed to sunlight. Most streams sampled in the region had high salinity levels (> 3,000 mg/L), and severely degraded riparian zones, invaded by introduced grasses and weeds, with cropping often occurring right up to the edge of the stream.
Seven sites were assigned either a Fair or Poor rating because their ecosystems showed evidence of moderate to major changes to animal and plant communities, and at least some changes to the way each ecosystem functioned. Most streams had salinities in the 3,000–9,000 mg/L range which is too high for the majority of freshwater macroinvertebrate species to tolerate. The Rocky, Light and Wakefield rivers, and Freshwater Creek were dominated by saline tolerant species that thrive in algal covered streams.
The eighth site sampled in the region, at Skillogallee Creek, was given a Very Poor rating because the ecosystem showed evidence of major changes to both the animal and plant life, and a significant breakdown in the way the ecosystem functioned because of grazing and drought effects.
Special environmental features
No rare or sensitive species were found at the sites sampled in spring 2008.
Only a few streams in the region have provided habitat for rare and sensitive macroinvertebrate species in the past. The most significant is Mary Springs, located on an unnamed stream that flows into Beetaloo Reservoir in the Crystal Brook and Broughton River catchments. It supported a wide range of notable species, including a stonefly (Dinotoperla evansi), mayflies (Atalophlebia, Nousia fuscula, Offadens), and various caddisflies (e.g. Orphninotrichia maculata and Apsilochorema gisbum) that are more typically found in the cooler and wetter streams from the southern Mount Lofty Ranges.
The Broughton River and lower Rocky River are also known to provide habitat for bristleworms from the family Syllidae, and the upper Skillogallee Creek provided habitat for mayflies (Atalophlebia australasica and Koorrnonga inconspicua) and a caddisfly (Taschorema evansi) during the 1990's.
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 Board is currently reviewing River Management Plans for:
Also 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)|
|Extensive introduced trees and weed growth in the riparian zone at the site and upstream (causing habitat disturbance).|
|Large nutrient inputs from numerous diffuse sources in the catchment (leading to extensive growth of algae and aquatic weeds).|
|Insufficient natural water flows (reducing ecological integrity).|