Drain M

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Glossary

Introduction

Drain M is one of many drain systems in the South East of the state. This fresh water drain discharges into Lake George near Beachport, where there have been algal blooms particularly during summer months. The dominant land use in the catchment is grazing, with pockets of irrigated cropping and forestry. Groundwater is very shallow in this region and the drain is designed to prevent flooding in the area and therefore provide more land for agriculture. Elevated nitrogen (mainly oxidised nitrogen) levels are often high because water soluble fertilisers leach through the soil and get transported to the drain through groundwater flows.

Many species of aquatic plants can be found in the channel, and the bank vegetation consists of sedges and exotic grasses. Stream flow for the Drain M catchment is available from the Department of Water, Land and Biodiversity Conservation.

>> Map (3MB PDF)

Water quality assessment

Water quality is assessed as being in good, moderate or poor condition by interpreting water chemistry data in the context of protecting environmental values. >> More

Ecological health is assessed in spring and autumn. We use macroinvertebrates for this purpose because they provide a relatively simple way to assess the health of an aquatic ecosystem. >> More

Water chemistry is measured each month. We measure chemical indicators because when they reach a certain level they can cause stress or toxicity to animals and plants in an ecosystem. Some indicators can also indicate if the water is suitable for drinking water or for activities such as swimming. >> More

Ecological health

We collect two samples of macroinvertebrates, one from riffle (or flowing water) habitat and one from edge (still water) habitat. The diversity of the macroinvertebrate community is used to describe ecological health as being in good, moderate or poor condition.

Go here to find out how we classify ecological health in streams.

Ecological health assessment for June 2006

Habitat	Ecological health
Edge	Moderate
Riffle	Habitat not present

Drain M was given a slightly impaired (moderate) ecological health rating in autumn 2006 and has been previously rated as good. The site had 29 different types of macroinvertebrates present. The most common were hydrobiid snails, oligochaete worms and amphipods (Austrochiltonia australis).

Similar to the nearby Drain L, a number of species were collected from the edge habitat that are more commonly found in of wetlands than in drains and creeks in the South East. They include waterbugs such as the corixid Diaprecoris barycephala and naucorid Naucoris congrex, and a rich dytiscid beetle fauna (Sternopriscus tasmanica, Megaporus hamatus, Rhantus suturalis, Lancetes lanceolatus).

Interestingly, only one chironomid midge larva was collected from the site, whereas normally samples have over 10-20 specimens from this dipteran family. The site also lacked any mayflies and leptocerid caddisflies, and had two introduced snails (Potamopyrgus antipodarum and Physa acuta) present.

The unusually low flows, poor habitat complexity and abundant growth of filamentous green algae contributed to the moderate condition of this site.

Download ecological health data

• All the macroinvertebrate data for Drain M (9KB CSV)

Water chemistry

The indicators that are measured in Drain M are nutrients (nitrogen and phosphorus), turbidity and salinity. The concentrations of these indicators are used to classify the water chemistry as being in good, moderate or poor condition, according to the needs of aquatic ecosystem protection.

Go here to find out how we organise and classify the chemistry data.

Water chemistry classification for April to September

Indicator	Classification
Oxidised Nitrogen	Good
Total Nitrogen	Poor
Soluble Phosphorus	Good
Total Phosphorus	Good
Turbidity	Good

Drain M is similar to Drain L, in being generally fed by groundwater flows that often have elevated nitrogen concentrations. The total nitrogen is probably derived from animal wastes being washed off farms during storms and percolating to groundwater that flows to the drain. Recent nitrogen (particularly oxidised nitrogen) concentrations may be lower than historical results. This is possibly linked to the drought, so will need to be monitored longer-term to determine whether it represents a trend.

The EPA Mt Gambier Office collaborates with the South East NRM Board, Primary Industries and Resources SA and The Department of Water, Land and Biodiversity Conservation on a project to enhance our understanding of the relationship between land use and nutrient transport.

Also, the EPA, South East NRM Board, Primary Industries SA and South East Drainage Board/The Department of Water, Land and Biodiversity Conservation are collaborating on a project to establish why the algal blooms are occurring in Lake George, including the role that Drain M has in contributing to this problem.

>> Archived results

Download water chemistry graphs

• Oxidised nitrogen in Drain M
  
• Total nitrogen in Drain M
  
• Total phosphorus in Drain M
  
• Soluble phosphorus in Drain M
  
• Turbidity in Drain M
  
• Salinity in Drain M

Download raw chemistry data

• All chemistry data for Drain M

What is being done to improve the condition of South Australian rivers and streams

Efforts to improve the condition of South Australia's rivers and streams are being driven by various government agencies, primarily

The Environment Protection Authority
The Department of Water, Land and Biodiversity Conservation
Natural Resource Management Boards
Department for Environment and Heritage (SA)

Collaborative projects and programs being run by these agencies are based on the protection of environmental values, as explained in the National Water Quality Management Strategy. >> More

This page was last modified 25-09-2007