Riparian and aquatic vegetation absent due to recent drain cleaning actions.
Area map
About the location
Drain 57 is a small drain, about 3.5 km 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 and Tantanoola paper and pulp mills. 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 and draining saline groundwater 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 southeast of Millicent. The site was accidentally sampled 100 metres upstream from the inflow of effluent from the pulp and paper mill instead of downstream of the discharge where the drain often holds water.
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 recent drain cleaning actions that resulted in the loss of any vegetation within the channel and banks. When vegetation recolonises the drain and provides some habitat and filtering functions, the condition of the site is likely to improve to either a Fair or Poor rating.
Findings
The site inspected in autumn and spring 2009 was dry, so macroinvertebrate and water quality data were not collected from this drain.
The sediments were dominated by sand, clay, gravel and pebble; samples taken from below the surface were aerobic.
No plants were growing in the channel or in the riparian zone because the drain had recently been cleaned by the drainage board to enhance the movement of water through the drain and prevent localised flooding during wet periods. The surrounding vegetation at the site was forestry plantation and cleared grazing land.
Special environmental features
None detected.
Pressures and management responses
Pressures
Management responses
Drought
The Drainage Network in the region supports nearly 200 regulators for water conservation and adaptive flows management practices. The freshwater weir pools of some regulators in the Lower South East are now known to support colonies of threatened aquatic species. The South Eastern Water Conservation and Drainage Board has undertaken preliminary investigations to identify additional biological hot spots in the Lower South East, and further investigations may be undertaken. This may lead to the installation of additional regulators to retain water as drought refuge at these key drain locations.
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 has undertaken a limited revegetation program at key locations, and has the ability to undertake further revegetation works when resources allow. 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.
Observed Condition
Expected Condition
