Drain 57, near Snuggery
2014 Aquatic Ecosystem Condition Report
- Permanent slow-flowing drain in autumn and spring 2014
- Sparse macroinvertebrate community with one flow-dependent species present
- Obvious evidence of gross nutrient enrichment
- Riparian vegetation dominated by introduced grasses and weeds
About the location
Drain 57 is a small drain, about 3.5 kilometres long in the South East. It rises at an elevation of about 20 metres above sea-level near the edge of the Mount Burr Range and receives runoff from agricultural land and discharge from the Millicent paper and pulp mill. It flows in a south-westerly direction into Drain 54 and ultimately discharges into Lake Bonney, SE via the English Gap Drain.
Drain 57 is an artificially constructed drain where the primary function is to remove surface water to improve agricultural productivity in the region (Department for Water 2010). Given its artificial character, the drain is not expected to be in a highly rated aquatic ecosystem condition, although it does provide significant habitat for many aquatic species in the region.
The monitoring site was located near Facey Road, about nine kilometres south-east of Millicent. The site was sampled downstream from the discharge of wastewater from the paper mill, whereas in 2009 it was assessed further upstream from the mostly dry section of drain.
The drain was given a very poor rating because the site sampled showed evidence of major changes in ecosystem structure and a significant breakdown to the way the ecosystem functions. There was considerable evidence of human disturbance due to the drain receiving a point source discharge of nutrient enriched wastewater from a pulp and paper mill, and the poor riparian and aquatic habitats associated with the drain.
A sparse community of at least 19 species of macroinvertebrates (9 in autumn and 17 in spring) was collected from the still to slow-flowing drain, 2.5 metres wide and over 72 centimetre deep, in autumn and spring 2014. The community was dominated by generalists and species tolerant to poor water quality such as introduced snails (Physiella) and chironomids (Cricotopus and Chironomus) and included smaller numbers of flatworms, leeches, worms, mites (Piona), native snails (Glyptophysa), amphipods, beetles, blackflies and waterbugs. The presence of active yabby holes in the banks indicated that they were a common inhabitant of this artificial watercourse. The drain lacked any rare or sensitive species and the only flow-dependent species collected was a blackfly (Simulium ornatipes); the latter are a type of filter-feeding fly larvae that commonly occurs in flowing water from organically polluted waters in South Australia.
The water was fresh (salinity ranged from 491-558 mg/L), well oxygenated (65-91% saturation), slightly coloured and turbid, and with high concentrations of nutrients such as nitrogen (2.82-3.35 mg/L) and phosphorus (0.12-0.16 mg/L).
The sediments were dominated by detritus, silt and filamentous algae (spring only), with smaller amounts of bedrock, boulder, sand and clay also present; samples taken from below the surface were black and grey silts that probably lacked oxygen for part of the year. There was no evidence of any bank erosion and no sign of any animal droppings in the vicinity of the site.
A large amount of phytoplankton was present (chlorophyll a ranged from 128-137 Âµg/L) which also included high concentrations of blue-green algae (evident from elevated chlorophyll b concentrations ranging from 6-29 Âµg/L), and filamentous algae (Cladophora) was only seen in spring when it covered over 35% of the drain. A similar area of the drain was covered by a submerged aquatic plant (Ruppia).
The narrow riparian zone consisted of introduced grasses and weeds with no trees or shrubs. The surrounding vegetation comprised cattle grazing paddocks and pastureland.
Special environmental features
Pressures and management responses
|Livestock having direct access (causing sediment erosion and adding excessive nutrients).||Drains have been constructed since the 1860s as an engineering solution to support agricultural development and it is South Eastern Water Conservation and Drainage Board practice to lease drain reserves for grazing in certain circumstances. Not all drains are subject to grazing and leases for grazing are only approved following an engineering and environmental assessment. Lease conditions require the lessee to fulfil pest plant, pest animal and CFS management requirements, thereby relieving the Board of these responsibilities.|
|Limited riparian zone vegetation (reducing habitat quality, increasing sediment erosion).||The South Eastern Water Conservation and Drainage Board maintains native vegetation cover where possible at key locations. Revegetation at biological hotspots is recognised as a mechanism to reduce nutrient input and soil erosion, and can be undertaken if it doesn’t impede access for management and maintenance.|
|Wastewater discharge, adding nutrients and organic matter (potentially leading to algal growth and aquatic weeds)||The Kimberly-Clark Paper Mill near Millicent has worked collaboratively with the South Australian Environmental Protection Authority (EPA) and the local community since 2007. We continue to work closely with the EPA to identify opportunities to further improve the quality of our waste water and reduce our water usage. This partnership has had a significant impact on the overall health of Lake Bonney, which was re-opened for recreational use in 2013 >>More information|