Professional divers are yet to undertake clean up of debris in the vicinity of the Nymboida River intake believed to be causing dirty water issues for the Regional Water Supply Scheme, however Clarence Valley Council have commenced extraction at different flow rates as a trial to assess if some water can be transferred to Shannon Creek Dam without turbidity affecting water quality.
Severe bush
fire damage in the Nymboida catchment over the summer, followed by heavy rain early in 2020, created high turbity (muddy water) in the Nymboida River so no water could be sourced to refill Shannon Creek Dam.
The water in the Nymboida River is now clear, but problems with high turbidity were experienced when starting to increase extraction to the rate needed to send water through the Regional Water Supply Scheme to Shannon Creek Dam and Karangi Dam. It is believed the water quality issue is being caused by the amount of bushfire ash and silt washed into the river. Several flushing programs to clean the tunnel and pipeline used to extract water from the Nymboida River did not resolve the water quality problem so investigations continue, with specialist divers set to inspect the tunnel and pipeline.
Until the issue is resolved and Shannon Creek Dam can be refilled with clean water from the Nymboida River, residents are reminded that water restrictions remain at Level One in the Coffs Harbour and Clarence Valley Local Government Areas, which are both served by the Regional Water Supply Scheme.
The smaller capacity Karangi Dam is being used to maintain Coffs Harbour water supply, with water sourced from the Orara River.
Daily Water Data
| | Sat | Sun | Mon | Tues | Wed | Thur | Fri | | 12/09/20
| 13/09/20
| 14/09/20
| 15/09/20
| 09/09/20
| 10/09/20
| 11/09/20
| CAPACITY & USE
| Combined Dams Capacity
| NA
| NA
| 90.4 %
| NA
| 90.5 %
| NA
| 90.3 %
| Karangi Dam Capacity
| NA
| NA
| 98.5 % | NA
| 98.3 %
| NA
| 98.0 %
| Karangi Dam Volume
(5,600ML)
| NA
| NA
| 5,514 ML
| NA
| 5,506 ML | NA
| 5,487 ML | Shannon Creek Dam Capacity | 89.2 %
| 89.2 %
| 89.2 %
| 89.4 %
| 89.3 %
| 89.2 %
| 89.2 %
| Shannon Creek Dam Volume
(30,000ML)
| 26,671ML
| 26,683 ML
| 26,667 ML
| 26,732 ML
| 26,699 ML
| 26,677 ML
| 26,669 ML
| Use -
(7-Day Average)
Target is 17ML/day
| 14.6 ML
| 14.0 ML
| 14.5 ML
| 14.4 ML
| 15.3 ML
| 15.3 ML
| 14.5 ML
| Backfeed to Clarence Valley Council | 0 ML
| 0 ML
| 0 ML
| 0 ML
| 0 ML
| 0 ML
| 0 ML
| EXTRACTION
| Orara River to Karangi Dam | 11.6 ML
| 25.8 ML
| 25.8 ML
| 10.7 ML
| 3.0 ML
| 3.6 ML
| 4.0 ML
| Nymboida River to Karangi Dam | 0 ML
| 0 ML
| 0 ML
| 0 ML
| 9.5 ML
| 1.0 ML
| 0 ML
| Nymboida River to Shannon Creek Dam | 0 ML
| 0 ML
| 17.6 ML
| 35.0 ML
| 14.5 ML
| 0 ML
| 0 ML
| Shannon Creek Dam to Karangi Dam
| 0 ML
| 0 ML
| 0 ML
| 0 ML
| 0 ML
| 0 ML
| 0 ML
|
|
|
Compliance Details
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The water we store in Karangi and Shannon Creek Dams to supply our drinking water is sourced from the Orara and Nymboida Rivers. There are two vital aspects to river water in these catchments which Council assesses to ensure our community has a safe and secure drinking water supply – water quantity and water quality.
Following heavy rain events, quantity may be well above minimum licenced environmental flow levels but quality issues can arise which prevent the extraction of this water into our dams for a period of time. Council monitors the water quality including turbidity levels – a measure of how much dirt is in the water - and will begin pumping once the quality tests indicate the river water is clean enough to take water from the rivers into our storage dams for our drinking water supplies.
Prior to the rainfall event in mid-January 2020, the last pumping from the Orara River occurred end of October, 2019. After the January rain, flows in the Orara River increased enough that Council was able to begin pumping after just a few days of waiting for the turbidity results to fall to clean water levels. This pumping ceased after 15 days – even though turbidity levels were good, the flows in the Orara River fell below environmental flow requirements.
Following the rainfall in mid-February, Orara River water levels again increased above environmental flow requirements and more than a week later, turbidity decreased to levels low enough to enable pumping from the river to commence. Regular rainfall throughout March has kept water levels in the Orara River above pumping cut-offs and turbidity has remained low so water pumped from the Orara River has topped up Karangi Dam.
The last time we were able to extract water from the Nymboida River was early August, 2019. Unfortunately, due to potential water quality issues caused by the devastating bushfires around Nymboida in November, 2019, Council was unable to pump any water from the Nymboida River following the January 2020 rainfall event. Even though this rain also increased flows in the Nymboida River above environmental flow levels, additional water quality tests were required to ensure rain runoff over the burnt catchment areas was not washing pollutants into the river which could negatively impact drinking water quality.
These tests were run again following further rain in February and have now indicated water in the Nymboida River is not being made unsafe for drinking by the bushfire disaster. However, turbidity levels in the Nymboida River are still too high and extraction will only commence once turbidity levels fall to indicate the water is clean enough to start re-filling Shannon Creek Dam. It is hoped that with the large amounts of rain received across the catchment, Nymboida River flows will remain high enough for long enough to allow Council to take clean water from the river so that Shannon Creek Dam can be once again filled to capacity.
Shannon Creek Dam is a storage dam built in the Shannon Creek catchment but only water pumped from the Nymboida River is permitted to be stored in Shannon Creek Dam.
The water licence from the NSW Government for Council to operate the Shannon Creek Dam requires that any rainfall which falls within the Shannon Creek catchment be released from the dam to continue its normal flow through the Shannon Creek catchment. This is to ensure that Shannon Creek Dam has minimal impact on the local Shannon Creek environment.
Even if we are on water restrictions at the time, releasing the water from the dam is a critical process to minimise the environmental impact of the dam and comply with our licence requirements.
Water Restrictions are based on the combined storage level of both Shannon Creek and Karangi Dams and will remain in place until all quantity and quality conditions are met to allow pumping from the Orara and Nymboida Rivers to re-fill our storage dams to adequate levels.
Council is constantly monitoring quality and quantity of water in the rivers, dam levels and community water consumption. We may also consider climate forecasts to ensure lifting of water restrictions is the best option for the long-term security of our drinking water supplies to avoid situations where restrictions are re-introduced shortly after lifting them.
