Drain E, near Lochaber Swamp
2014 Aquatic Ecosystem Condition Report
- Dry when sampled in autumn and spring 2014
- Likely to be grossly enriched with nutrients when wet due to the surrounding land uses
- Riparian vegetation comprising introduced grasses and bare soil
- Stock access banks and channel throughout the year
About the location
Drain E is a large drain in the South East with a catchment area of more than 690 square kilometres. It rises at an elevation of about 100 metres above sea-level near Kybybolite as Naracoorte Creek, where it flows in a westerly direction through Naracoorte and discharges into Lake Ormerod. The drainage from this lake is where Drain E commences and it ultimately discharges into a series of wetlands called the Marcollat watercourse, to the west of Padthaway.
Drain E 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 major land use is sheep and cattle grazing, and the upstream Naracoorte Creek also receives wastewater from the Naracoorte Wastewater Treatment Plant. The monitoring site was located off Canes Road, about 21 kilometres north-west from Naracoorte.
The drain was given a poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions.The ephemeral nature and limited riparian habitat within a heavily grazed catchment are likely to contribute to large algal growths, as well as other signs of gross nutrient enrichment, when water is present in this drain.
The sediments were dominated by sand, detritus and clay; samples taken from below the surface were aerobic grey silts but the sediments probably turn anaerobic whenever the channel holds water and starts to dry, due to the decomposition of the organically enriched sediments. No areas of significant bank erosion were noted during either survey but cattle appeared to have been able to regularly access the banks and bed of the drain in 2014, given the extent of cattle droppings distributed throughout the drain.
No aquatic plants or evidence of any dry filamentous algae were recorded at the site, highlighting that this drain rarely holds water for extended periods. The narrow riparian zone lacked any trees and shrubs and comprised heavily grazed introduced grasses and bare soil. The surrounding terrestrial vegetation consisted of cattle grazing paddocks with a few scattered gums present in the local landscape.
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 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 does not impede access for management and maintenance.|
|Wastewater discharges, adding excessive nutrients and organic matter (leading to algal growth and aquatic weeds)||
SA Water Naracoorte Wastewater Treatment Plant
SA Water assess and undertake scheduled process improvement actions at the wastewater treatment plant, with the aim to reduce environmental risk and ensure operations are compliant with EPA licence conditions.