Victoria Creek, Williamstown
2008 Aquatic Ecosystem Condition Report
- Affected by moderate to high nutrient levels.
- Diverse macroinvertebrate community dominated by species tolerant of pollution.
- Large growths of algae and aquatic plants.
- Riparian zone invaded by weeds.
About the location
Victoria Creek rises to the east of Williamstown in the Mount Lofty Ranges, and flows through Williamstown into the northeastern corner of the South Para Reservoir. Livestock grazing and forestry are the major land uses in the upper reaches of the catchment where there are also significant areas of remnant native vegetation. Vineyards, livestock grazing and urban living dominate the mid to lower reaches.
The monitoring site was situated off South Para Road in Williamstown, next to a small concrete weir.
The creek was given a Fair rating at this site because the ecosystem showed moderate changes to animal and plant life, and some changes to the way the ecosystem functions. Urban stormwater and runoff from agricultural land contributed to high nutrient levels and significant growths of algae and aquatic weeds.
The only flowing water at the time of sampling in November 2008 was over the concrete weir. A series of still, connected pools provided habitat for a diverse community of 53 macroinvertebrate species, however more than 60% of the community were species tolerant to high nutrient levels such as introduced and native snails and worms. No sensitive or rare species were collected.
The water was fresh (salinity of 712 mg/L) and well oxygenated (67% saturation). It was clear, although strongly coloured from natural tannins, and had moderate to high concentrations of nutrients such as nitrogen (0.98 mg/L), phosphorus (0.07 mg/L) and oxidised nitrogen (0.16 mg/L).
Green filamentous algae (Cladophora and Spirogyra) covered most of the creekbed which was made up mostly of bedrock, cobbles, silt and detritus. The sediments were blackened and anaerobic, suggesting too much organic material had entered the creek.
Vegetation within the creek channel included watermilfoil (Myriophyllum), Narrow-leafed Cumbungi (Typha domingensis), rush (Juncus), Stiff Flat Sedge (Cyperus vaginatus), Watercress (Rorippa nasturtium-aquaticum) and Sharp Clubrush (Schoenoplectus pungens). River Red Gums and introduced ash trees dominated the riparian zone, growing over native shrubs and weeds such as blackberries, boxthorn and Salvation Jane. Urban gardens set within a linear park covered the surrounding area.
Special environmental features
The deeper pools in the creek provided habitat for tadpoles of the Eastern Banjo Frog (Limnodynastes dumerili), a commonly occurring frog in the Adelaide Hills.
Pressures and management responses
|Livestock have direct access at the site and upstream, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||The Adelaide and Mount Lofty Ranges NRM Board's land management program encourages and promotes managing land to improve water quality. This includes incentives for waterway and wetland fencing to exclude or limit stock from entering riparian zones.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for revegetation programs around waterways and wetlands and stock exclusion as well as educating landholders about the importance of riparian vegetation in managing soil erosion.|
|Large decrease in natural water flows during summer months (reducing ecological integrity).||Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.|
|Stormwater runoff causing high water velocities, containing nutrients and sediments (causing habitat disturbance, algal growth and aquatic weeds).||The Adelaide and Mount Lofty Ranges NRM Board has a well developed stormwater quality improvement, harvesting and reuse program which has installed (and maintains) gross pollutant (and silt) traps in several watercourses across the region to catch litter, debris and silt in order to minimise impacts and damage to seagrass in the receiving marine environment. Stormwater captured is also treated through artificial wetlands across the region which act as suspended solid and nutrient filters; these wetlands also provide important habitat for many native species.|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA and prepared in conjunction with the Adelaide and Mount Lofty Ranges NRM Board.