Canberra

Water for environmental, social and cultural benefit

Water management areas and guidelines

The ACT Government Department of Environment, Climate Change, Energy and Water identifies and manages water for ecosystems under the Water Resources Act 2007 (ACT). The 2006 Environmental Flow Guidelines is a statutory instrument that is used to determine allowable volumes when licensing the taking of water. These guidelines are consistent with the Territory Plan 2008 and use the precautionary principle in accordance with the Intergovernmental Agreement on the Environment (1992).

Environmental flow requirements

The environmental flow requirements for ACT are of the rules-based type (e.g. translucent passing of natural inflows). In the National Water Account 2010, these requirements are deemed unregulated. Summaries of these environmental flow requirements from the 2006 Environmental Flow Guidelines are presented in the following table.

It should be noted that percentile flows within the Environmental Flow Guidelines refers to the flow at which a certain percentage of the measured data exceeds. For example, the 80th percentile is defined as the flow that is exceeded at least 80% of the time.

Flow	Ecosystem category	Reach	Flow requirement
Base flows
	Water supply ecosystems	Above Corin Dam	Maintenance of all natural flows
		Above Googong Dam and any impoundment on the Naas and Gudgenby rivers	Maintenance of all natural flows except those needed for stock and domestic purposes, and that already provided for at the time these guidelines are listed
		Below Corin Dam	Maintain 75% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less
		Below Bendora Dam	Maintain 75% of the 80th percentile of the monthly natural inflow, or inflow, whichever is less
		Below Cotter Dam	Maintain an average flow of 15 ML/day
		Below Googong Dam	Maintain an average flow of 10 ML/day or natural inflow, whichever is less
		Below any impoundment on the Naas and Gudgenby rivers	Maintain an average flow of 10 ML/day or natural inflow, whichever is less
	Natural ecosystems	All reaches in natural ecosystems	Maintain 80th percentile monthly flow in all months Abstractions may not exceed flow rate
	Modified ecosystems	Murrumbidgee River	Maintain 80th percentile monthly flow November–May, and 90th percentile monthly flow June–October inclusive Abstractions may not exceed flow rate
	Modified ecosystems	Other reaches in the ACT in modified ecosystems	Maintain 80th percentile monthly flow in all months Abstractions may not exceed flow rate
	Created ecosystems	All reaches in created ecosystems	Maintain 80th percentile monthly flow in all months Abstractions may not exceed flow rate
Riffle maintenance flows
	Water supply ecosystems	Below Corin Dam	Maintain a flow of 150 ML/day for 3 consecutive days every 2 months
		Below Bendora Dam	Maintain a flow of 150 ML/day for 3 consecutive days every 2 months
		Below Cotter Dam	Maintain a flow of 100 ML/day for 1 day every 2 months
		Below Googong Dam	Maintain a flow of 100 ML/day for 1 day every 2 months
		Below any impoundment on the Naas and Gudgenby rivers	Maintain a flow of 100 ML/day for 1 day every 2 months
	Natural ecosystems	All reaches in natural ecosystems	No requirement
	Modified ecosystems	All reaches in modified ecosystems	No requirement
	Created ecosystems	All reaches in created ecosystems	No requirement
Pool maintenance flows
	Water supply ecosystems	Below Corin Dam	Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid-October
		Below Bendora Dam	Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid-October
		Below Cotter Dam	No requirement
		Below Googong Dam	No requirement
		Below any impoundment on the Naas and Gudgenby rivers	No requirement
Channel maintenance flows
	Natural ecosystems	All reaches in natural ecosystems	Protect 90% of the volume in events above the 80th percentile from abstraction
	Modified ecosystems	All reaches in the ACT including the Murrumbidgee River	Protect 90% of the volume in events above the 80th percentile from abstraction
	Created ecosystems	All reaches in created ecosystems	Protect 90% of the volume in events above the 80th percentile from abstraction
Groundwater abstraction limits
	Water supply ecosystems	All reaches	Groundwater abstraction is limited to 10% of the long-term recharge
	Natural ecosystems	All reaches in natural ecosystems	Groundwater abstraction is limited to 10% of the long-term recharge
	Modified ecosystems	All reaches in the ACT including the Murrumbidgee River	Groundwater abstraction is limited to 10% of the long-term recharge
	Created ecosystems	All reaches	Groundwater abstraction is limited to 10% of the long-term recharge
Impoundment drawdown levels
	Water supply ecosystems	Cotter Reservoir	An adaptive management program will be used to guide drawdown to protect habitat for Macquarie perch
	All other water supply impoundments	No limits are placed on drawdown levels
	Natural ecosystems	All natural lakes or ponds	No abstraction is permitted from natural lakes or ponds
	All other impoundments	Drawdown is limited to 0.20 m below the spillway¹
	Modified ecosystems	All impoundments	Drawdown is limited to 0.20 m below the spillway¹
	Created ecosystems	All impoundments	Drawdown is limited to 0.20 m below the spillway¹
Drought flows for water supply ecosystems Stage 1 restrictions
Base flows
		Above Corin Dam	Maintenance of all natural flows
		Above Googong Dam and any impoundment on the Naas and Gudgenby rivers	Maintenance of all natural flows except those needed for stock and domestic purposes, and that are already provided for at the time these guidelines are listed
		Below Corin Dam	Maintain a flow of 40 ML/day or 75% of the 80th percentile of the monthly natural inflow, or natural inflow, whichever is less
		Below Bendora Dam	Maintain a flow of 40 ML/day or 75% of the 80th percentile of the monthly natural inflow, or natural inflow, whichever is less
		Below Cotter Dam	Maintain an average flow of 15 ML/day
		Below Googong Dam	Maintain an average flow of 10 ML/day or natural inflow, whichever is less
		Below any impoundment on the Naas and Gudgenby rivers	Maintain an average of 10 ML/day or natural inflow, whichever is less
Riffle maintenance flows
		Below Corin Dam	Maintain a flow of 150 ML/day for 3 consecutive days every 2 months
		Below Bendora Dam	Maintain a flow of 150 ML/day for 3 consecutive days every 2 months
		Below Cotter Dam	No requirement
		Below Googong Dam	No requirement
		Below any impoundment on the Naas and Gudgenby rivers	No requirement
Pool maintenance flows
		Below Corin Dam	Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid-October
		Below Bendora Dam	Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid-October
		Below Cotter Dam	No requirement
		Below Googong Dam	No requirement
		Below any impoundment on the Naas and Gudgenby rivers	No requirement
Drought flows for water supply ecosystems Stage 2 restrictions or above
Base flows
		Above Corin Dam	Maintenance of all natural flows
		Above Googong Dam and any impoundment on the Naas and Gudgenby rivers	Maintenance of all natural flows except those needed for stock and domestic purposes, and that are already provided for at the time these guidelines are listed
		Below Corin Dam	Maintain an average of 20 ML/day
		Below Bendora Dam	Maintain an average of 20 ML/day
		Below Cotter Dam	Maintain an average of 15 ML/day
		Below Googong Dam	Maintain an average of 10 ML/day or inflow, whichever is less
		Below any impoundment on the Naas and Gudgenby rivers	Maintain an average of 10 ML/day or natural inflow, whichever is less
Riffle maintenance flows
		Below Corin Dam	Maintain a flow of 150 ML/day for 3 consecutive days every 2 months
		Below Bendora Dam	Maintain a flow of 150 ML/day for 3 consecutive days every 2 months
		Below Cotter Dam	No requirement
		Below Googong Dam	No requirement
		Below any impoundment on the Naas and Gudgenby rivers	No requirement
Pool Maintenance Flows
		Below Corin Dam	Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid-October
		Below Bendora Dam	Maintain a flow of >550 ML/day for 2 consecutive days between mid-July and mid-October
		Below Cotter Dam	No requirement
		Below Googong Dam	No requirement
		Below any impoundment on the Naas and Gudgenby rivers	No requirement

1 For urban lakes and ponds constructed after these guidelines, the maximum drawdown as a result of abstraction is 0.20 metres below spillway level, or a lower level if it can be demonstrated that a pond has been explicitly designed to fulfil its required water quality and ecological functions under the proposed drawdown regime.

National Water Account 2010