Water Extraction
The water equilibrium for the Nepean Peninsula is in debit by approximately 1.3 GL/yr. This is consistent with observed water level regressions and may well be due to a blend of reduced rainfall and increased groundwater extraction. This situation will eventually lead to greater intrusion of saline groundwater into the freshwater aquifer and this risk should be further calculated.
An analysis of the potential extraction rates of groundwater through licensed, stock and domestic bores in the study area was completed in 2010. The Nepean Peninsula has had the most growth in stock and domestic bores, with 40% (figure 3) of all total licences for the area having been granted in the last 5 years to 2010, and with more than 60% of the total potential groundwater extraction (0.8 Giga-litres per year from stock and domestic bores and 5.2 Giga-litres per year from licensed bores). There has also been a significant increase in stock and domestic bores near the coast in other parts of the study area of the Nepean Peninsula.[1]
All groundwater extraction needs to be managed to prevent the Tootgarook Swamp being lost from salination and acidification.
If left undisturbed and covered in water, sulfidic materials[2] (or prospective acid sulfate soil, figure 4) pose little or no threat. However, when exposed to oxygen through drying under drought conditions or from excavating or dredging, chemical reactions may lead to the formation of sulfuric materials[3] (pH < 4) or actual acid sulfate soil and the generation of sulfuric acid. When sulfuric materials are exposed to water again, there is a risk that significant amounts of sulfuric acid are released which can cause the acidification of wetlands and estuaries. Other heavy metals and metalloids (such as arsenic) can also be mobilised.
Acidification of waterways, wetlands, and estuaries leads to massive fish kills. In turn, deoxygenation of the water can lead to toxic algal blooms. Acid has also been linked to chronic effects on aquatic systems that include disease, reduced hatching survival and growth rates for a wide range of species.
Degradation of the ecology of wetlands, shallow freshwater and brackish aquifer systems through loss of water quality causes degradation of habitat and decline in dependent ecosystems. Apart from the direct affect of acid production which causes fish kills and the decline in number and diversity of invertebrate populations, acidification and heavy metal toxicity can have a negative impact on macrophytes and other aquatic vegetation that aquatic animals depend on for food, shelter and reproduction. Loss of aquatic animal life can, in turn, have serious consequences for other species along the food chain, such as birds. Sulfuric materials in CASS (coastal acid sulphate soil) can potentially affect important breeding and feeding habitat for various waterbirds, including migratory species listed under international agreements such as JAMBA and CAMBA.
Acid sulphate release can cause corrosion of concrete and steel infrastructure, such as foundations and footings, culverts, pipes (including drinking water conduits), bridges and floodgates, reducing their functional life span. The costs associated with damage to public and private infrastructure is significant.
Immediate detrimental human health effects such as skin and eye irritations and burns. The long-term impacts of exposure to heavy metals on human health are not well understood but are thought to include increased risks of cancers (skin and lung) and skin lesions. Water polluted by toxic quantities of soluble heavy metals has led to human and animal ill health. Corrosion of pipes can also lead to contamination of drinking water supplies and increased sewerage spills.
Irreversible change to landforms and soils.
It is now recognised that certain environmental effects of the oxidation of acid sulfate soils can last for hundreds and thousands of years. Acid discharge can lead to changes in the soil fabric, leading to irreversible shrinking and lowering of ground surfaces.
Disturbance refers to any activity that disturbs or alters the sulfidic materials in CASS and causes oxidation. Types of activities that have a high risk of disturbing CASS are:
• excavating soil;
• filling land;
• moving soil from its pre-activity location (horizontally or vertically);
• temporarily or permanently dewatering soil; and
• causing CASS to be temporarily or permanently bathed in oxidised water
(as opposed to the low oxygen content water in which it is normally submersed).
[1] Groundwater Resource Appraisal for Southeast Melbourne – Southern Rural Water Authority 2010
[2] Sulfidic material is any soil, sediment or peat layer that contains metal sulfides (generally pyrite or iron sulfide; FeS2). This material only exists under oxygen free or Anaerobic , waterlogged conditions.
[3] Sulfuric material is any soil, sediment or peat layer (horizon) that contains sulfuric acid (H2SO4). Sulfuric acid is produced by oxidation of sulfidic material.
An analysis of the potential extraction rates of groundwater through licensed, stock and domestic bores in the study area was completed in 2010. The Nepean Peninsula has had the most growth in stock and domestic bores, with 40% (figure 3) of all total licences for the area having been granted in the last 5 years to 2010, and with more than 60% of the total potential groundwater extraction (0.8 Giga-litres per year from stock and domestic bores and 5.2 Giga-litres per year from licensed bores). There has also been a significant increase in stock and domestic bores near the coast in other parts of the study area of the Nepean Peninsula.[1]
All groundwater extraction needs to be managed to prevent the Tootgarook Swamp being lost from salination and acidification.
If left undisturbed and covered in water, sulfidic materials[2] (or prospective acid sulfate soil, figure 4) pose little or no threat. However, when exposed to oxygen through drying under drought conditions or from excavating or dredging, chemical reactions may lead to the formation of sulfuric materials[3] (pH < 4) or actual acid sulfate soil and the generation of sulfuric acid. When sulfuric materials are exposed to water again, there is a risk that significant amounts of sulfuric acid are released which can cause the acidification of wetlands and estuaries. Other heavy metals and metalloids (such as arsenic) can also be mobilised.
Acidification of waterways, wetlands, and estuaries leads to massive fish kills. In turn, deoxygenation of the water can lead to toxic algal blooms. Acid has also been linked to chronic effects on aquatic systems that include disease, reduced hatching survival and growth rates for a wide range of species.
Degradation of the ecology of wetlands, shallow freshwater and brackish aquifer systems through loss of water quality causes degradation of habitat and decline in dependent ecosystems. Apart from the direct affect of acid production which causes fish kills and the decline in number and diversity of invertebrate populations, acidification and heavy metal toxicity can have a negative impact on macrophytes and other aquatic vegetation that aquatic animals depend on for food, shelter and reproduction. Loss of aquatic animal life can, in turn, have serious consequences for other species along the food chain, such as birds. Sulfuric materials in CASS (coastal acid sulphate soil) can potentially affect important breeding and feeding habitat for various waterbirds, including migratory species listed under international agreements such as JAMBA and CAMBA.
Acid sulphate release can cause corrosion of concrete and steel infrastructure, such as foundations and footings, culverts, pipes (including drinking water conduits), bridges and floodgates, reducing their functional life span. The costs associated with damage to public and private infrastructure is significant.
Immediate detrimental human health effects such as skin and eye irritations and burns. The long-term impacts of exposure to heavy metals on human health are not well understood but are thought to include increased risks of cancers (skin and lung) and skin lesions. Water polluted by toxic quantities of soluble heavy metals has led to human and animal ill health. Corrosion of pipes can also lead to contamination of drinking water supplies and increased sewerage spills.
Irreversible change to landforms and soils.
It is now recognised that certain environmental effects of the oxidation of acid sulfate soils can last for hundreds and thousands of years. Acid discharge can lead to changes in the soil fabric, leading to irreversible shrinking and lowering of ground surfaces.
Disturbance refers to any activity that disturbs or alters the sulfidic materials in CASS and causes oxidation. Types of activities that have a high risk of disturbing CASS are:
• excavating soil;
• filling land;
• moving soil from its pre-activity location (horizontally or vertically);
• temporarily or permanently dewatering soil; and
• causing CASS to be temporarily or permanently bathed in oxidised water
(as opposed to the low oxygen content water in which it is normally submersed).
[1] Groundwater Resource Appraisal for Southeast Melbourne – Southern Rural Water Authority 2010
[2] Sulfidic material is any soil, sediment or peat layer that contains metal sulfides (generally pyrite or iron sulfide; FeS2). This material only exists under oxygen free or Anaerobic , waterlogged conditions.
[3] Sulfuric material is any soil, sediment or peat layer (horizon) that contains sulfuric acid (H2SO4). Sulfuric acid is produced by oxidation of sulfidic material.
