River issues

Yrka has summarised five issues concerning the Yarra River, and developed its “position” on each of them.

(i) Riverside development and planning

The natural corridor of the Yarra is vital to Melbourne’s amenity and liveability. It provides some of the most popular green open spaces for recreating and enjoying a natural setting, and hence is vital to community well-being. It is also rich habitat for native plants and animals, and for many species the continuity and vegetation of the river corridor are vital for their survival.

But the green environs of the Yarra continue to shrink from the pressure of urban growth and encroaching development. In the Lower Yarra the erection of huge apartment buildings is the most obvious problem, but just as damaging is the cumulative impact of many developments on single home sites. In the upper reaches of the river, the problem is that indigenous vegetation is being cleared to make way for expanding suburbia, infrastructure, new golf courses and the like.

Healthy river environs

Healthy river environs

Building encroaching onto the riverine landscape

Building encroaching onto the riverine landscape

 

(ii) River flows and water supply

The health and values of the Yarra are closely linked to its water flows – both the quantity and the variability/pattern of flows. The native plants and animals that live in and by the river have evolved in sympathy with its flows. Many aspects of their lives (and thus the biodiversity) are dependent on different flow levels and flow “events”. Examples are – a short period of high flows to trigger Macquarie Perch spawning – inundation of a wetlands for nesting water fowl– alternating high and low water levels as needed by River Red Gums.

But the capture and extraction of the Yarra’s water (by dams and pumps) to supply residences, factories and farms in the Greater Melbourne area has significantly altered both the quantity and pattern of river flows.

The program to release environmental flows down the Yarra which commenced in September 2011 is helping restore some of the natural flow pattern; but not all of the natural flows (eg inundation of floodplains) can be so restored.

In contrast no effort is being made to restore the natural quantity/level of flows, or size of the river. The river’s size governs the abundance of species, and has social values, being a factor in the river’s heritage, and water based recreation such as paddling. (NB We are not advocating big floods that would damage property or assets above the natural floodplain.)

Healthy river flows

Healthy river flows

Dangerously low flows

Dangerously low flows

(iii) Water quality and pollution

As widely acknowledged, the ecological and social values of the Yarra are dependent on it being pollution-free. The different forms and sources of water pollution include:

  • litter and solid waste (so-called gross pollution) which has either been dropped or spilt in the catchment,
  • disease-causing bacteria, coming mainly from leaking/overflowing sewerage systems but also contaminated stormwater, and organic waste,
  • sediments contained in stormwater and runoff from cleared land, construction sites and dirt roads,
  • nutrients coming mainly from sewage treatment plant effluent, cleared land, parks and gardens,
  • other damaging chemicals (eg hydrocarbons, heavy metals and pesticides) coming mainly from stormwater run-off in urban streets and agricultural land. Heavy metals are also present in the river sediments and a legacy of past practices.

Some pollutants are directly harmful to animals and humans. Other pollutants will trigger unnaturally high levels of turbidity and algae, and low dissolved oxygen, which in turn are harmful.

river_issues3

Stormwater pollution

Litter caught in a litter trap

Litter caught in a litter trap

(iv) Flora and fauna

The environmental and social values of the Yarra are related to it being home for a wide variety of plants and animals, especially indigenous species. However, the number and population of native species are severely affected by the spread of introduced species, notably weeds, exotic fish, domestic stock and feral animals. Nonetheless the circumstances vary widely along the river and across the catchment. In the older urban areas exotic garden plants and pet animals are valued by the community. On sporting fields and golf links, open mowed exotic grass is the norm. In agricultural areas, stock animals and food crops are intended. It is in the parks, bushland and the waterway itself where the objective is for only indigenous species.

Revegetation with indigenous plant species is being undertaken by many community groups and most local authorities, and there are numerous success stories. But the attractiveness of exotic plants and animals, and the fact that many out-compete native species are formidable barriers, such that it is doubtful whether the overall situation is improving.

(v) Other social values

The community values the Yarra in ways beyond those described above. These social values include its rich human heritage (both aboriginal and post-European settlement); the many forms of recreation beside and on the river; its inspiration to artists, photographers, authors and poets; the personal stories and associations with it; and the role the Yarra plays in civic and cultural events and celebrations.

Furthermore, the extent to which the community values the river has an important impact on its environmental values, because “people protect what they love.”