Rocky Creek Dam

Water quality

Rocky Creek Dam Water Quality Compliance

Sample type Sample count Number of characteristics Number of non-compliant samples Compliance (%)
Physical 714 1762 0 100
Chemical 161 1561 0 100
Microbiological 702 0 100

Routine Drinking Water Monitoring Characteristics

Rocky Creek Dam Chronic health-related Chemical Water Quality data

Characteristic Guideline value 5th percentile Mean 95th percentile Maximum Sample count Meeting Guideline value (%)
Antimony (mg/L) 0.003 <0.0001 <0.0001 12 100
Arsenic (mg/L) 0.01 <0.001 <0.001 12 100
Barium (mg/L) 2 0.0023 0.0033 12 100
Boron (mg/L) 4 0.0116 0.0132 12 100
Cadmium (mg/L) 0.002 <0.0001 <0.0001 12 100
Chromium (mg/L) 0.05 <0.001 <0.001 12 100
Fluoride (mg/L) 1.5 0.59 0.94 12 100
Iodine (mg/L) 0.5 <0.02 0.02 12 100
Lead (mg/L) 0.01 <0.0002* <0.001* <0.005* <0.005* 161 100
Manganese (mg/L) 0.5 <0.0003* <0.001* <0.005* <0.005* 161 100
Mercury (mg/L) 0.001 <0.0008 <0.0008 12 100
Molybdenum (mg/L) 0.05 0.0001 0.0002 12 100
Nickel (mg/L) 0.02 <0.0004 <0.0004 12 100
pH 6.5 - 8.5 6.9 7.4 7.8 8 714 100
Selenium (mg/L) 0.01 <0.007 <0.007 12 100
Silver (mg/L) 0.1 <0.0002 <0.0002 12 100
Uranium (mg/L) 0.02 <0.0001 <0.0001 12 100

Chronic health-related chemical characteristics are inorganic chemicals that might be present in water and can pose a risk to health with prolonged exposure. The Guideline values for these materials are usually set to be protective over a lifetime of exposure. Single results above a Guideline value are unlikely to pose a risk to health; compliance is based on analysing long term trends.

* Limits of reporting vary between samples. The highest recorded lead concentration in 2024 that was above the corresponding limit of reporting was 0.002 mg/L. The highest recorded manganese concentration in 2024 that was above the corresponding limit of reporting was 0.0006 mg/L. Neither of these results have been explicitly included in Table 2 due to other samples having higher limits of reporting.

Rocky Creek Dam Acute health-related Chemical Water Quality data

Characteristic Guideline value 5th percentile Mean 95th percentile Maximum Sample count Meeting Guideline value (%)
Copper (mg/L) 2 0.003 0.021 0.054 0.36 161 100
Nitrate (mg/L) 50 <1 1 12 100
Nitrite (mg/L) 3 <0.1 <0.1 12 100

Acute health-related chemical characteristics are inorganic chemicals that can pose a health risk based on a small number of exposures. High concentrations of copper can cause vomiting. High concentrations of nitrite can be risky for bottle-fed babies. The Guideline values for these characteristics have been set to protect people from short-term exposure.

Rocky Creek Dam Physical and Selected Aesthetic Chemical Water Quality Data

Characteristic  Guideline value 5th percentile Mean 95th percentile Maximum Sample count Meeting Guideline value (%)
Iron (mg/L)  0.3 <0.001* <0.005* 0.006 0.009 161 100
Sodium (mg/L)  180   14   17 12 100
Total dissolved solids (mg/L) 10000   83   97 12 100
Total hardness (mg/L) 200 52 57 63 66 161 100
True Colour (HU) 15 0 1 2.5 8 161 100
Turbidity (NTU) 5 0.16 0.28 0.38 3.9 714 100

Physical and aesthetic chemical characteristics change the way that water appears; its taste, smell, look and feel. These characteristics do not have health guideline values but do affect how people feel about their drinking water.

*Limits of reporting vary between samples.

Rocky Creek Dam Microbiological Water Quality Data

Characteristic Guideline value 5th percentile Mean 95th percentile Maximum Sample count Meeting Guideline value (%)
E. coli (cfu/100ml) <1 <1 <1 <1 <1 702 100
Free Chlorine 0.2 - 5 0.41 0.89 1.4 2.5 702 100

Escherichia coli, a bacteria found in the gut of many backboned animals, is an indicator that there has been recent contamination with faeces in a drinking water supply. Chlorine is used widely to kill disease-causing organisms in drinking water. A reasonable residual concentration in the supply provides ongoing protection all the way to customer taps, and gives some indication that filtration is working well and the distribution system has not been compromised.

Other monitoring

Disinfection Byproduct Testing

Rocky Creek Dam Disinfection Byproduct Data

Characteristic Guideline value Mean Maximum Sample count Meeting Guideline value (%)
Total trihalomethanes (ug/L) 250 30 49 11 100

Disinfection byproducts are formed by the reaction of chlorine and natural organic material in the water. They can pose a risk to health with prolonged exposure. The Guideline values for these materials are set to be protective over a lifetime of exposure.

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