Residual Flows

Background

An aim of this plan change is to provide greater certainty around the values considered when setting a residual flow, the method used and where and how a residual flow may be set or measured.

What is this plan change about?

Currently, when considering an application to take water, the Water Plan requires ORC to assess whether a ‘residual flow’ is required, and if so, this can be included as a condition on the permit. These existing provisions have been in the plan from the time it became operative in 2004.

A ‘residual flow’ is a quantity of water that must be left in the river at the point of take. When setting a residual flow condition, the existing policies require ORC to consider the effects of a take on the aquatic ecosystem and natural character of the water body.


Why is the plan change needed?

Since becoming operative in the Water Plan in 2004, we have noticed some issues with these provisions. We know there is confusion about:

· When a residual flow condition applies to a water permit,

· How to calculate what a residual flow level will be, and

· What the difference is between minimum and residual flows and how they work together.

There is a lack of flexibility when it comes to where a residual flow is measured. Currently the measurement is required to be taken at the point of water take, which is not always practical e.g. access might be poor. This also limits those wanting to measure a residual flow as a group.

Also the existing provisions requires natural character and aquatic ecosystem values to be considered when setting a residual flow condition. What we have heard is that these are not the only values which people would like to see being considered when setting a residual flow.

What does the plan change aim to do?

Through this plan change ORC seek to provide certainty around residual flow setting by:

· Providing a method to calculate a residual flow

· Setting out a broader list of values for consideration in assessment – such as including cultural values and consideration of downstream users

· Enabling flexibility so that the location of where a residual flow is measured is practical and can also enable one measurement site for a group of water permits

Who will be affected by the plan change?

The plan change will amend parts of the Water Plan that relate to the taking of water. If you currently have a water permit, or a deemed permit and are looking to replace this permit or you are thinking of applying for a new permit to take water, then this plan change may affect you.

What is the difference between a Minimum Flow and a Residual Flow?

Residual flows apply as a condition on individual water permits, and they specify the flow of water that is to be left in the river immediately downstream of the water take. They are typically applied to tributaries.

Minimum flows are set on the main stem of flow and apply as a condition. Therefore, permits within the catchment will be required to stop taking water when the river flow reaches the minimum flow set.

It is important to note that in some instances both a minimum flow and a residual flow may apply as condition on a water permit.

Background

An aim of this plan change is to provide greater certainty around the values considered when setting a residual flow, the method used and where and how a residual flow may be set or measured.

What is this plan change about?

Currently, when considering an application to take water, the Water Plan requires ORC to assess whether a ‘residual flow’ is required, and if so, this can be included as a condition on the permit. These existing provisions have been in the plan from the time it became operative in 2004.

A ‘residual flow’ is a quantity of water that must be left in the river at the point of take. When setting a residual flow condition, the existing policies require ORC to consider the effects of a take on the aquatic ecosystem and natural character of the water body.


Why is the plan change needed?

Since becoming operative in the Water Plan in 2004, we have noticed some issues with these provisions. We know there is confusion about:

· When a residual flow condition applies to a water permit,

· How to calculate what a residual flow level will be, and

· What the difference is between minimum and residual flows and how they work together.

There is a lack of flexibility when it comes to where a residual flow is measured. Currently the measurement is required to be taken at the point of water take, which is not always practical e.g. access might be poor. This also limits those wanting to measure a residual flow as a group.

Also the existing provisions requires natural character and aquatic ecosystem values to be considered when setting a residual flow condition. What we have heard is that these are not the only values which people would like to see being considered when setting a residual flow.

What does the plan change aim to do?

Through this plan change ORC seek to provide certainty around residual flow setting by:

· Providing a method to calculate a residual flow

· Setting out a broader list of values for consideration in assessment – such as including cultural values and consideration of downstream users

· Enabling flexibility so that the location of where a residual flow is measured is practical and can also enable one measurement site for a group of water permits

Who will be affected by the plan change?

The plan change will amend parts of the Water Plan that relate to the taking of water. If you currently have a water permit, or a deemed permit and are looking to replace this permit or you are thinking of applying for a new permit to take water, then this plan change may affect you.

What is the difference between a Minimum Flow and a Residual Flow?

Residual flows apply as a condition on individual water permits, and they specify the flow of water that is to be left in the river immediately downstream of the water take. They are typically applied to tributaries.

Minimum flows are set on the main stem of flow and apply as a condition. Therefore, permits within the catchment will be required to stop taking water when the river flow reaches the minimum flow set.

It is important to note that in some instances both a minimum flow and a residual flow may apply as condition on a water permit.