Land and natural environment

Over 94% of the native vegetation in the local government area has been cleared. The remaining 6% exists in pockets and is threatened by isolation, grazing and weed invasion. The main areas of native vegetation remaining are on rocky ridgelines such as the McPherson Range, low lying areas such as black Box depressions and swamps and roadsides.

Less native vegetation usually indicates less native wildlife, as well as increased likelihood of salinity. Records show there are 29 threatened species, including frogs, bats and birds that are likely to occur in the local government area.

Council, Murrumbidgee Irrigation and Landcare Groups have been replanting native vegetation for a number of years within the region in an effort to manage salinity problems, provide a more beautiful environment, and care for our wildlife.

In the city area, planting of natives has been undertaken at recharge sites such as Scenic Hill (usually upslope, where rainfall sinks into the ground) and discharge sites such as Clifton Boulevard (usually down slope, where groundwater rises to the surface). This program of planting will be continuing into the future.

Useful links

NSW Department of Environment & Heritage
NSW Department of Planning
Office of Local Government NSW
Murrumbidgee Irrigation
NPWS Cocoparra National Park Profile

Salinity

What is Salinity?

Salts are a natural part of the landscape in Australia and are found in the rocks, soil and shallow groundwater. Some salt is also carried within rain drops. Changes in land use over time have caused salts normally stored in soils and rocks to be dissolved in water and brought to the surface. When the water evaporates, the salts concentrate at or near the lands surface, and salinity can become a problem. It should be remembered though that whilst salt occurs naturally, the way we use and manage our land and water resources has a large impact on salinity.

Like many urban areas, Griffith and its villages are located in a salty landscape. Over watering of lawns, gardens and sporting fields can cause the groundwater to rise to the surface, bringing with it salts. Leaky pipes (stormwater, town water supply and sewage) and swimming pools can also cause water table levels to rise. Urban salinity can also be related to sub-surface water flows being impeded by structures such as roads and by poor drainage conditions. There may also be some influence to the mobility of salt and watertable depth locally, due to the use of water in the surrounding irrigation area.

Salinity damage shortens the life of urban infrastructure such as roads, buildings, paving, water and sewage pipes and can have detrimental effects on vegetation such as trees, gardens, lawns and playing fields. This leads to costly maintenance and repair by homeowners and councils.

To manage urban salinity the problem normally needs to be addressed at both the catchment (the surrounding rural and urban landscape) and local levels. This is because the groundwater responds to both catchment and local factors. Management practices within an urban centre alone are not normally sufficient.

At the local level, in the urban centre itself, there a number of management strategies that councils and residents could implement. These include:

  • Avoiding over-watering public parks, sports fields, home gardens and lawns
  • Planting large native trees and shrubs in open spaces
  • Investigating the extent of leaking channels and pipes and implementing a pipe replacement program using corrosion resistant materials
  • Assessing the likelihood that current and proposed water storages, artificial lakes and drainage basins contribute to groundwater recharge, with strategies to minimise where possible
  • Ensuring that water drains away from infrastructure developments to avoid ponding
  • Connecting septic tanks to piped sewerage systems where possible
  • Connecting roof drainage to stormwater systems, rather than sullage pits
  • Monitoring changes to watertable levels and groundwater quality by installing piezometer ('monitoring bore') networks
  • Encouraging residents to establish gardens with low water requirements.
  • New houses, buildings or infrastructure in current or potentially salt-affected areas should be built to withstand the effects of salinity. Corrosion resistant materials should be widely used. Durable water-resistant membranes (eg. damp courses in houses) may often be appropriate.

Find out more about Urban Salinity here(PDF, 3MB)

Hypoxic Blackwater

The Department of Planning, Industry and Environment (DPIE) have informed Local Government Areas (LGA’s) of possible Hypoxic Blackwater Events throughout the Riverina and Murrumbidgee Catchment area due to wetter than normal conditions.

  • Following three hot, dry years, floodplains across the Basin have high leaf litter and grass loads and have not been flushed since 2016.
  • Forecasts for the Southern Basin show we are currently in a La Niña cycle. There is potential for high rainfall and flooding in late 2020 to early 2021, similar to late 2016.
  • River managers, scientists and environmental water holders are monitoring rivers for potential hypoxic Blackwater and working to reduce impacts of a hypoxic Blackwater event where they can.

What is Hypoxic Blackwater?

‘Blackwater’ is a term used when high levels of organic material and tannins in a river discolour the water making it appear black. The water can then become hypoxic (low oxygen) when the material decomposes reducing the oxygen in the water. Blackwater events occur during flooding when organic material is washed off the river bank and floodplain and into the river system.

Most hypoxic Blackwater events happen after prolonged dry periods such is happening now, when temperatures are warm and there has been an extensive build-up of organic material, such as leaf litter.

Some native fish and crustacea are especially vulnerable to oxygen deprivation. Fish are sometimes able to escape the most badly affected areas by swimming upstream or downstream. The chemicals released from organic material can also make water bodies more alkaline or acidic, potentially resulting in toxic effects on some aquatic organisms.

Is there a risk to humans?

Risks to human health are low if direct contact with hypoxic Blackwater is avoided. Thorough cleansing is advised after any contact with affected water and discoloured or dead fish should not be eaten because of possible health risks.

Will Blackwater have an effect on Lake Wyangan?

At this stage it is highly unlikely that Lake Wyangan will be affected by Blackwater as this type of event occurs mainly in rivers and/or lakes that are fed directly by rivers.

Further information

The Department of Environment and Energy has information on hypoxic blackwater events and water quality.

Visit the Murray–Darling Basin Authority website to learn more about blackwater.

Real-time water data by WaterNSW includes DO values for some river gauges in NSW.

Tharbogang Swamp

The lesser known of the wetlands in the Lake Wyangan system, the Tharbogang Swamp is ephemeral and often dry but received a huge influx of water during the March 2012 floods.  Some of this water still remains, though the water is steadily receding.

Once a healthy Black Box depression, many of the trees have died from excessive drainage water and rising salt levels and the ground is fragile and eroded in some areas.  The surrounding land is used for grazing and horticulture. 

Despite its state, the swamp attracts hundreds of waterbirds including Black Swan, Pacific Black Duck and Eurasian Coot, with a variety of many other species.  A pair of White-bellied Sea-eagles have been sighted over the north end of the wetland.  Silver Gulls were amongst others nesting on the raised dry banks in the middle of the wetland.

Council received funding from the NSW Government Office of Environment and Heritage Environmental Trust Restoration and Rehabilitation Grant Program during 2013.  These funds are being utilised at the site for replacement of fencing, direct seeding to encourage increased diversity and revegetation of the eroded areas, weed and pest control.  A Cultural Survey has also been undertaken at the site with many artefacts recorded. 

Members of the Murrumbidgee Field Naturalist Club (MFN) and the general public were invited to a field day at the Tharbogang Swamp in November 2013 and a week later, the swamp was also visited by 33 members of the premier Sydney bird watching group, the Cumberland Bird Observers.

Future field days are planned for the site.  Contact Councils Environment Planner should you wish find out more.

 

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