A total of 5 sites were sampled from streams in the Barossa Valley and 5 sites from in or near the Clare Valley within the Northern and Yorke Landscape SA region. Land use is dominated by agricultural stock grazing, cereal cropping and vineyards, with only a small area of remnant native vegetation occurring in the region.
According to the Bureau of Meteorology, a slightly lower than average rainfall was recorded across the state in 2021, with a very dry September but the wettest November on record. The mean annual temperature was 0.36°C above average. Consequently, when samples were taken from the region in late November–early December, stream conditions should have represented typical, well-watered conditions for the sampled sites.
Sites monitored in spring 2021 were considered to be in a Good to Poor condition. No sites were assigned to the Excellent, Very Good or Very Poor classes. Given the scale of vegetation clearance, it is unrealistic to expect any stream to be unaffected by human activities.
Of the sites assessed, 1 site (10%) was in Good condition with only minor changes to animal and plant life, 6 sites (60%) were in Fair condition with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned, and 3 sites (30%) were in Poor condition with moderate changes to the way ecosystems functioned.
The best site was located in the mid-reaches of Jacob Creek which was well-lined by vegetation and supported at least 52 macroinvertebrate species from flowing and stillwater habitats. The stream had a salinity of about 880 mg/L when sampled.
In contrast, the more degraded sites assigned to the Fair and Poor condition classes were from cleared agricultural catchments with little to no remnant native vegetation, macroinvertebrate communities dominated by 13–33 tolerant and generalist species, with limited riparian habitats and waters enriched with nutrients and fine sediment, and most with salinities well over 1,000 mg/L.
Aquatic macroinvertebrate communities were dominated by tolerant and generalist macroinvertebrate species, including an amphipod crustacean (Austrochiltonia), snails (introduced Physa and native Glyptophysa), chironomids (Procladius, Paramerina, Cricotopus, Paratanytarsus, Chironomus, Dicrotendipes and Polypedilum) and waterbugs (Micronecta, Microvelia, Sigara and Anisops). Most streams also supported lower numbers of flatworms, worms, shrimp and different damselflies and dragonfly larvae (eg Ischnura, Austrolestes, Hemianax and Hemicordulia).
Regionally significant species were only recorded from flowing water habitats at Jacob Creek, including riffle beetles (Family Psephenidae), trickle midges (Family Thaumaleidae), blackfly larvae (Austrosimilium), mayflies (Offadens, Atalophlebia, Thraulophlebia) and caddisflies (Ulmerochorema and Taschorema).
Other notable species found in riffle habitats from a few streams in the region included snails Angrobia and introduced Potamopyrgus), another blackfly species (Simulium) and a caddisfly (Cheumatopyche). These species require well-oxygenated, flowing water and, apart from the latter 2 species, do not occur in streams that rarely flow or are covered in algae, or with salinities over 3,000 mg/L.
Most streams in the region were distinguished by the presence of a narrow (<5 m up to 10 m wide) riparian zone comprising River Red Gums over weedy grasses. The exception was at Jacob Creek, which extended up to 30 m wide but also consisted of River Red Gums and weedy ash trees over woody weeds such as blackberries and gorse, and an understorey of weeds and introduced grasses.
The water quality of sampled sites showed a wide variation in measured parameters, with most enriched by nitrogen and phosphorus concentrations >0.5 mg/L and >0.2 mg/L, respectively.
Barossa Valley streams had chlorophyll concentrations ranging from 6–42 µg/L, nitrogen from 0.45–1.79 mg/L, phosphorus from 0.01–0.18 mg/L, and field conductivity from 1,464–4,717 µS/cm.
Clare Valley streams had lower chlorophyll a concentrations ranging from 4–8 µg/L, often lower nitrogen concentrations from 0.29–0.91 mg/L, sometimes higher phosphorus levels from 0.01–0.24 mg/L, and stream conductivity ranged from 310–26,310 µS/cm.
Most sites sampled showed evidence of nutrient enrichment with a macrophyte cover extending over 10% of the sampled channel and the presence of obvious growths of the filamentous alga Cladophora.
The most notable record was the presence of the riffle beetle larvae Sclerocyphon (Family Psephenidae) and trickle fly larvae (Family Thaumaleidae) from Jacob Creek. Both species have been rarely collected in the Mount Lofty Ranges and have a restricted distribution to permanently flowing, less disturbed streams such as First and Sixth Creeks.
Previous work in the Barossa Valley has recorded similar species assemblages from Jacob Creek but few rare or sensitive species appear to inhabit the main channels of the North or South Para Rivers or other tributary streams.
Sites from the Clare Valley have not been assessed since 2008 but streams from the North Para River were last assessed as part of the Western Mount Lofty Ranges region in 2018.
Previous work in the Clare Valley noted that Mary Springs provided the most significant habitat for several notable species, including stoneflies (Dinotoperla evansi), mayflies (Atalophlebia, Nousia fuscula, Offadens) and caddisflies (Orphninotrichia maculata, Apsilochorema gisbum) that are more typically found in the cooler and more permanently flowing freshwater streams in the Southern Mount Lofty Ranges.
Previous sampling in the upper Skillogallee Creek during the 1990s also recorded mayflies (A. australasica and Thraulophlebia inconspicua) and caddisflies (Taschorema evansi). None of these species were recorded from the sampled streams in 2021, and given their apparent restricted distribution, it is possible that some may no longer occur in the Northern and Yorke Landscape region.