Lower Molonglo Catchment

  • One priority project, including the establishment of two wetlands, has been chosen for the Lower Molonglo catchment.
  • An estimated $9.6 million will be invested in the catchment over three years.
  • Research indicates the project will remove 5% of suspended solids, 5% of phosphorus and 2% of nitrogen from Lower Molonglo waterways.

Proposed priority projects

Wetlands – Cotter Road south of Pearlman Street, Wright

Two wetlands will be established in the open space between Dixon Drive and Cotter Road in the suburb of Holder.  The wetlands will help remove nutrients from stormwater by providing a habitat for water-loving reeds, grasses and trees which use the nutrients to grow.  They will also help to remove sediments by reducing the speed of water flows.

The wetlands will be positioned to minimise impact on existing vegetation and paths which are currently used for walking, horse riding and cycling.  The area will be extensively landscaped to maintain amenity.

Wetlands can attract a large diversity of wildlife, such as birds and frogs, as well as providing opportunities for recreation and the enjoyment of nature.  It is expected that the site will become a picnic destination for walkers and cyclists.

Catchment Facts

  • Encompasses the Molonglo River downstream of Lake Burley Griffin, below Scrivener Dam to the Murrumbidgee River.
  • Receives inflows from tributaries including Yarralumla Creek, Weston Creek and Coppins Creek.
  • Flows also come from Canberra’s main sewage treatment plant, known as the Lower Molonglo Water Quality Control Centre.
  • The catchment area on each side of the river corridor consists of undulating open grassy woodland and grazing land zoned for current and future residential development.
  • The main tributaries from the southern side (Yarralumla Creek and Weston Creek) incorporate standard residential development that commenced in the 1960s.
  • New and proposed urban developments (including Molonglo Stage 1, 2 and 3) all drain directly into the Molonglo River through minor drainage networks that treat run-off in line with Water Sensitive Urban Design (WSUD) principles.
  • The Molonglo 3 development presents an opportunity to undertake monitoring on a greenfield site before, during and after residential development.
    Total Area – 86.40km2 

Land Use Zone

Area (km2)

Area (ha)

Area (%)

Pervious Area

57.19

5719.15

66.20%

Low Density Residential

0.12

12.21

0.14%

Medium Density Residential

17.67

1766.99

20.45%

High Density Residential

1.33

133.27

1.54%

Commercial and Industrial

2.04

203.83

2.36%

Transport

8.04

804.10

9.31%

Lower Molonglo – Totals

86.40

8639.55

100%

Water Quality Issues

  • The sewage treatment plant (STP) is the largest source of nutrient discharge within the ACT, even though the water meets health & environment standards.
  • However, urban areas are the greatest source of untreated pollution within the Catchment.
  • Research indicates the highest levels of pollution in the catchment occur in the Yarralumla, Weston Creek, Coombs and Wright urban areas.
  • These sources effect water quality in the Molonglo River, upstream of discharge from the sewage treatment plant.
  • Elevated nutrients and electrical conductivity in the Murrumbidgee River reflect the combined STP discharge and urban pollution sources.

Catchment options

The ACT Government is committed to improving the accessibility of web content. To provide feedback or request an accessible version of a document please contact us or phone 13 22 81.