Marcollat Watercourse, near Bimbimbi Swamp
2014 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2014
- Likely to be nutrient enriched when wet due to the surrounding land uses
- Riparian vegetation limited to a sparse cover of paperbarks over introduced grasses
- Only fine sediments and detritus occur throughout this section of the watercourse
About the location
Marcollat Watercourse consists of a series of swamps and wetlands linked by both naturally occurring and man-made channels in the lower South East. The watercourse extends over about 30 kilometres and has a catchment area covering over 1,900 square kilometres. It starts near the south-western edge of the interdunal flat between Harper Range and Stewart Range, and flows north-west towards Jip Jip Conservation Park.
Marcollat Watercourse is part of an artificially constructed drain network 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 watercourse 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 uses are grazing and cropping, and the wetlands and swamps within the catchment include areas of remnant native vegetation. The monitoring site was located off Rowney Road, about 18 kilometres west-north-west from Padthaway.
The watercourse 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 due to the limited native vegetation and aquatic habitat present within and on the banks of this watercourse.
The sediment was dominated by sand, detritus, silt and clay; samples taken from below the surface were aerobic grey sands. No evidence of any bank erosion was noted and the only animal droppings seen on the banks and within the channel were from rabbits.
No aquatic plants were growing in the channel or on the water’s edge, suggesting water rarely pools in this section of the watercourse.
The riparian zone consisted of scattered patches of paperbarks over introduced grasses and weeds. The surrounding vegetation was pasture and sheep grazing land with some scattered gums in the local landscape.
Special environmental features
Pressures and management responses
|Limited water flow||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 does not impede access for management and maintenance.|