State water agencies manage licences for overland flows. We protect overland flows through our overland flow licences. These licences help to secure environmental benefits for the Lower Balonne region and downstream into the Barwon–Darling.
What is overland flow?
Overland flow is also known as floodwater. It is a natural process where water moves across the landscape. It plays a crucial role in maintaining the health of our waterways and ecosystems.
Overland flow can happen because of rainfall and flooding.
When soil is so wet it can't absorb any more water, excess water flows over the ground forming watercourses. This water ends up joining waterways, such as rivers, creeks and wetlands.
Below are some images of overland flow in action. They show how Commonwealth’s overland licences connect the Balonne River to its floodplain.
The white arrows show the overland flow path. It passes through Lake Munya on ‘Kia Ora’ (a large station) then reconnects with the Balonne River. Photo: Sentinel Playground. February 2020.
The black arrow shows floodwater entering the ‘Kia Ora’ property. It flows into Lake Munya at the bottom. Photo: Greg Whyte. February 2020.
The black arrow shows overland flows going into the Balonne River. It flows over decommissioned works on the ‘Kia Ora’ property. Photo: Greg Whyte. February 2020.
The white arrows show overland flows on the Narran River floodplain. It flows between decommissioned storages on the ‘Clyde’ property. Photo: Sentinel playground. February 2020.
The black arrow shows overland flow on the Narran River floodplain. It flows over the ‘Clyde’ property. Photo: Scott Balsillie.February 2020.
The black arrows show overland flow going over the Narran River floodplain, on the ‘Clyde’ property. This shows another view of the decommissioned storage #11. Photo: Scott Balsillie. February 2020.
The importance of overland flow
As rivers rise, water flows into other channels and onto surrounding land. The water carries nutrients, sediment and organic matter to the floodplain. This makes it more fertile for plant growth.
Overland flows that start on floodplains have the same benefits. This provides benefits to the river downstream.
Regardless of where the overland flows start from, they provide water for plants and wildlife, and ecological benefits downstream.
Overland flow licences in the Balonne River
We hold overland flow licences in the Lower Balonne.
Water availability varies from year to year, and we can only access water from our overland flow licences at high flow rates. To access our permanent licence holding, flow rates at St George need to be 30,000 megalitres per day or more. Past flow records show these licences get activated every few years.
In February 2020, a lot of rain led to a flow rate of almost 200,000 megalitres per day at St George. This triggered a lot of overland flow licences, including ours, which added to flows across the Lower Balonne. As a result, the Narran Lakes received a large flow for the first time in 7 years.
Our role in overland flow management
We use overland flow to improve river, wetland and floodplain health in the Lower Balonne.
On-farm levees and structures previously connected to these licences were removed. This allows water to flow freely across the land and back to the river.
Queensland’s water harvesting announcement system protects water going back to the river. This allows it to flow downstream. The system also protects water in low areas of the floodplain, which isn't for consumptive use.