Analyzing Water Quality in Mt Lofty Ranges
The citizens of Adelaide rely on seven reservoirs scattered along the catchments of the Mount Lofty Ranges (MLR) for their drinking water, supplemented as needed with water diverted from the River Murray.
However unlike the protected water supply catchments of most other Australian capital cities, the Adelaide catchments also support both agriculture and urban and rural populations. Land-use conflicts and declining water quality have been an inevitable result.
Until recently, authorities working on local water quality and management issues in these critical and highly complex catchments have lacked both local data sets and easy means for estimating nutrient loads entering the water supply. This will result in better information for organisations responsible for water management.
Nigel Fleming, a project member from the South Australian Research and Development Institute (SARDI), says WQA is supporting his use of eWater’s Source Catchments software to predict the movement of runoff, sediment and nutrients for a range of scenarios.
Fleming says WQA is proving a handy way to apply known and trusted analysis methods to data sets, without demanding scientific expertise.
Initial water quality analysis work on the project relied on the use of constituent generation parameters (EMC/DWC values) from South East Queensland, focussing on total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN). There was little variation between land uses for these EMC/DWC values and the data sets, being based on work undertaken in a significantly different climate, were considered a poor representation of local data.
To resolve this issue Fleming’s team has been updating previous models to better represent the water quantity and quality in the Mount Lofty Ranges.
WQA has now allowed teams to develop locally derived EMC/DWC values for TSS, TN and TP. The comprehensive analysis of up to 30 years of composite sampler flow and load data using a range of tools (including the eWater Water Quality Analyser) has produced high quality event and baseflow data for 14 functional units (land use types) specifically in the MLR but also for greater South Australia. The localised data has increased the confidence external stakeholders place in outputs produced by Source Catchments models produced in South Australia.
“The values are assigned to land uses, and we’re confident that the values we’ve developed relate to the land uses in our geographical region because they are actually calculated from measured data from those regions,” Fleming says. “It’s actually a remarkably good data set and we are very fortunate to have it.”
The work involved analysing data from more than 500 weekly sample sets for several monitoring points, then using WQA to define the required time period and values to be analysed.
“Then all we had to do was push a button and WQA calculated the EMC values for us. That would have taken a huge amount of time to do in a spreadsheet,” he says. “I did some of the calculating work but I also had a couple of people working with me who did the bulk of it and they were able to pick up WQA quite readily so I am very happy with it as a tool.
“I am fairly new to this field and for me the biggest advantage of the tool was being able to take a data set, and using the tool quite readily apply known and trusted analysis methods to get the results and compare them. In combination with eWater’s River Analysis Package (RAP), WQA is proving really useful. I have not used river data much and it has been great to be able to examine and transform data sets, determine high and low flow periods and work out which is base flow and which is peak flow in a data set.
“It is the sort of thing you can do manually but it takes a very long time unless you can find a tool that you’re confident that is doing the job. It makes life much easier and it is an objective tool. People can get the same data set, use the same tool and get the same results,” Fleming says.
The Mount Lofty Ranges watershed catchments cover around 1600 km2 and are a vital part of Adelaide’s water supply. The Region features both unspoilt bushland and a diverse mosaic of land uses, including agriculture, horticulture and urban usage. A highly productive agricultural area with fertile soils and reliable annual rainfall, the MLR is under pressure from burgeoning human activity and is facing a changing climate, landscape, and hydrological regime. It has five major rivers: Gawler, Torrens, Little Para, Sturt and Onkaparinga.
The catchments play a central role in Adelaide’s water supply, providing storage for River Murray water and runoff following rains.
As the most biologically diverse region in South Australia, MLR contains many species unique to the region as well as half of the State's species of native plants and three quarters of its native birds. The Australian Government declared the area one of 15 Biodiversity Hotspots in Australia in 2003. Mixed land use leads at time to water contamination and complicates environmental flow management, demanding a multi-layer management approach.
The state’s natural-resource managers are juggling the environmental and human demands for water resources. The long term health of the catchments is important not only for inhabitants and ongoing land-use activities, but also for addressing the city’s burgeoning water needs. An associated project is also assessing likely ecological responses to flow patterns in regulated river reaches. The outputs will guide management actions and water-release decisions.
The project teams have been using eWater’s Source Catchments software to model the relationship between land-use, climate, water-quality and flow, and the impacts these have on supporting viable fish populations. Team members come from SA Environment Protection Authority, SARDI, the Department for Water, SA Water Corporation and CSIRO.
The work uses the Event Mean Concentration/Dry Weather Concentration (EMC/DWC) method to characterise pollutant concentrations in receiving waters from a runoff event. This involves taking water samples in proportion to the flow rate (proportional sampling) then compositing these into a single sample for analysis.