Bremer River, near Callington
2015 Aquatic Ecosystem Condition Report
Permanently wet, moderately freshwater stream with slow-flowing habitats in autumn and areas of faster-flowing riffles present in spring
Moderately diverse macroinvertebrate community with one sensitive stonefly
Obvious signs of moderate nutrient enrichment
Riparian vegetation was mostly introduced grasses, reeds and lignum
About the location
Bremer River is a large stream in the southern Mount Lofty Ranges, rising east of Harrogate and flowing in a southerly direction where it ultimately discharges into Lake Alexandrina. The major land uses are sheep grazing and cropping. The monitoring site was located at the Jaensch Road ford, about six kilometres south of Callington.
The river was given a fair rating because the site sampled showed moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of human disturbance, including nutrient enrichment, fine sediment deposition and poor riparian habitat.
A moderately diverse community of about 35 species of macroinvertebrates (19 species in autumn and 26 in spring) was collected or seen from the flowing river, 1.4-8 metres wide and over 1 metre deep, in autumn and spring 2015. The river consisted of slow-flowing pool and riffle habitats in autumn and flowing pools and areas of fast-flowing riffle habitats in spring. The community was dominated by species tolerant to poor water quality such as caddisflies (Triplectides australicus) and waterbugs (Micronecta) in the pools in autumn, whereas the same habitats in spring were dominated by amphipods (Austrochiltonia), introduced snails (Physiella) and chironomids. The flowing riffle habitats were dominated by sensitive, flow-dependent species such as blackflies (Simulium ornatipes) and stoneflies (Riekoperla naso) in autumn but in spring these habitats supported large numbers of amphipods and chironomids. Many other species were present in smaller numbers during the year, including worms, mites (including Coaustraliobates, Limnesia and Arrenurus), snails (mostly introduced Physiella), freshwater shrimp, yabbies, amphipods, beetles and chironomids. A few notable taxa were collected at the site including rare, sensitive and flow-dependent elmid beetles and larvae (Coxelmis v. fasciatus) and the sensitive stonefly and flow-dependent blackfly larvae. A single Flathead Gudgeon (Philypnodon grandiceps) was the only fish recorded from the site in autumn.
The water was moderately fresh (salinity ranged from 1,140-1,502 mg/L), well oxygenated in autumn but poorly oxygenated in spring (25-67% saturation), clear and strongly coloured in spring, and with moderate to high concentrations of nutrients such as nitrogen (0.51-1.59 mg/L) and phosphorus (0.03-0.12 mg/L).
The sediments in the pools were dominated by living and dead detritus and silt, whereas the riffles comprised mostly detritus, boulder and silt. Samples taken from below the surface were grey silts and clays that did not release sulfide when tested, indicating the sediments were well oxygenated. A deposit of 1-5 centimetres of silt covered the streambed downstream from the ford in autumn but had increased to over 10 centimetres deep in spring; presumably this was caused by the deposition of fine sediment from the gravel road crossing the site during winter rainfall events.
Moderate to large amounts of phytoplankton were present (chlorophyll a ranged from 2.3-4.9 µg/L) but no filamentous algal growths were recorded during either 2015 survey. Aquatic plants covered more than 65% of the site in both autumn and spring, largely due to the extensive growth of the Common Reed (Phragmites) and sedges (Bolboschoenus). The narrow 5 metre wide riparian zone mostly consisted of introduced grasses, reeds and lignum (Muehlenbeckia), with some gum trees and weeds also present. The surrounding vegetation was cropping and grazing land with only a few scattered gum trees present.
Special environmental values
The most notable records for the site included the presence of the elmid beetle in spring and the stonefly and flow-dependent blackfly in autumn; the latter two taxa were also collected from the same site in 2010.
Congolli, a native fish species identified as vulnerable in the 2009 ‘Action plan for South Australian freshwater fishes’, has been found downstream of this site near Hartley within the last five years (Nick Whiterod, Aquasave Consultants, pers. comm.)
Pressures and management responses
Livestock have direct access to some creeks, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).
Natural Resources SA Murray–Darling Basin acknowledges the significant impacts that livestock have on aquatic environments and seeks to provide free technical advice and incentives to land managers for fencing and other works as funding permits. Funding incentives are limited in value and extent and require land managers to volunteer to be involved.
Limited riparian vegetation at some creeks, providing minimal buffer protection from catchment landuses (reducing habitat quality).
Natural Resources SA Murray–Darling Basin recognises that the management of riparian vegetation requires a long-term, integrated approach to achieve ecosystem benefits. The NRM Board therefore provides free technical advice on a range of topics for land managers and various incentives for works as funding permits.
|Insufficient natural water flows resulting from water extraction and climate variability (reducing ecological integrity).||A water allocation plan that guides sustainable water use in the Eastern Mount Lofty Ranges has been developed by Natural Resources SA Murray–Darling Basin, working with the community and government (particularly the Department for Environment, Water and Natural Resources (DEWNR)). The plan aims to balance social, economic and environmental water needs and is implemented through a system of water licensing and permits for water affecting activities administered by DEWNR. A key component of the water allocation plan is to provide water to sustain the environment at an acceptable level of risk. Securing low flows for the environment is a key environmental water provision in this area, and Natural Resources SA Murray–Darling Basin is working together with DEWNR, Natural Resources Adelaide and Mount Lofty Ranges and the community to develop a program to secure low flows across the Mount Lofty Ranges. For more information on water allocation planning and associated projects go to our Water Allocation Planning web page.|