Benara Creek, Lake Bonney SE
2009 Aquatic Ecosystem Condition Report
- Creek was dry in autumn and spring 2009.
- Likely to show at least some signs of nutrient enrichment when water is present based on land uses in the catchment.
- Riparian vegetation consists of remnant low coastal woodland over a weedy understorey.
About the location
Benara Creek is a small stream in the lower South East with a catchment area of about 66 km2. It rises at an elevation nearly 20 metres above sea-level about eight kilometres south of Tantanoola, and drains in a southwesterly direction where it discharges into the southern part of Lake Bonney SE.
The major land uses are grazing sheep and cattle, wind power generation and small areas of pine plantations and remnant vegetation. The monitoring site was located on Three Chain Road, about 14 km northwest of Kongorong and two kilometres east of Lake Bonney SE.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. However, much of the catchment upstream is cleared and grazed by sheep and cattle, so nutrient enrichment indicators are likely to become more evident when this ephemeral creek flows. This may result in the condition of this stream being downgraded to probably either a Fair or Poor rating.
The site was dry in autumn and spring 2009 so aquatic macroinvertebrate and water chemistry data were not available for the creek.
The sediments were dominated by detritus, clay, sand and silt, and showed no signs of being anaerobic. The creek is, however, expected to become anaerobic when water pools at the site due to decomposition of the large buildup of organic matter that is present in the sediments.
The channel had no aquatic species present but the riparian zone extended for up to 15 metres from the edge of the channel and consisted of native tea tree and wattles over a wide range of weeds and grasses. A similar vegetation assemblage occurred over the surrounding landscape near the site but a few hundred metres upstream and downstream of the site the catchment was dominated by introduced grasses with small patches of trees and shrubs.
Special environmental features
Benara Creek provides habitat for tea trees (Leptospermum), an uncommon native plant in the region.
Pressures and 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.|