Overland flow is water that runs across the land after rainfall, either before it enters a watercourse, after it leaves a watercourse as floodwater, or after it rises to the surface naturally from underground.
It does not include:
- water that has naturally infiltrated the soil in normal farming operations
- irrigation tailwater if its recycling meets best practice requirements
- water collected from roofs for rainwater tanks.
Most water in our rivers and underground reserves originates as overland flow water. Capturing and storing this water is referred to as overland flow development. This development can reduce the volume of water entering streams and rivers and therefore impact on water available for pasture, woodlands, towns and farms.
How overland flow is managed
You can take overland flow for any purpose unless there is a moratorium notice or a water plan that limits what can be taken. Rules in the Water Regulation 2016 and related codes established under the Water Act 2000 regulate the building of new works that actively or passively take overland flow.
A water plan may:
- regulate existing works that take overland flow
- state management rules aiming to protect the security of existing water entitlements and environmental water needs.
Where the construction of overland flow works is regulated, the development may be either assessable or accepted development under the Planning Act 2016.
If overland flow water is regulated in your area, you may need to apply for a water licence.
Contaminated overland flow
Overland flow water that is contaminated with chemicals used in agriculture needs to be captured to prevent harm to streams and rivers.
However, capturing more than what is needed to prevent harm can impact on other water users and environmental needs.
Existing works for taking overland flow are those:
- legally constructed under a moratorium
- as defined under the water plan.
Notification of existing works
The relevant water plan for your area includes notification requirements for existing overland flow works.
If you are not sure about the capacity of existing works, you can have the works formally certified by an accredited engineer or surveyor.
Maintaining existing works
You can continue to maintain or repair existing works in an area where overland flow is regulated to ensure they continue to operate. You must not increase the capacity of the works to contain overland flow as a result of maintenance or repair.
- de-silting the storage (not deepening)
- repairing embankments, bywash facilities, pipes and pumps.
You should contact your local business centre before carrying out any maintenance or repairs or to find out more about overland flow in specific water plan areas.
You may take overland flow water for any purpose unless there is a moratorium notice or water plan that limits or alters the water that may be taken.
Regulating new works
Building new works to take overland flow water is regulated under the Planning Act 2016. This applies to works identified as either assessable or accepted development in a water plan or the Water Regulation 2016.
Moratoriums can be declared to suspend construction of new works for taking overland flow as part of the water planning process. This ensures that all existing uses are properly accounted for and that no further development takes place while a water plan is being developed. Moratoriums can continue until a water management protocol is in place.
Before constructing assessable overland flow works a landholder must hold a development permit. Assessable development requires approval from the State Assessment and Referral Agency.
Accepted development must comply with the relevant code. Under these codes, you must notify the Department of Regional Development, Manufacturing and Water of any new works within 60 days of their completion. This enables the department to monitor changes in water use within the catchments, and the data will be used in future water planning.
Acceptable development includes works to take overland flow water:
- for stock or domestic purposes
- using limited capacity works (as limited in certain water plans)
- for environmentally relevant purposes.
For further information on overland flow, contact your local business centre.