The upper Ovens River is one of the last major rivers in the Murray-Darling Basin which retains a near natural flow regime. Although largely unregulated, water is harvested by pumping to fill farm dams, to irrigate crops and for domestic, stock and town use. In dry years, consumptive demand has the potential to significantly reduce or stop flow. Low flows and cease-to-flow events can have negative impacts on aquatic fauna by reducing the quality or quantity of aquatic habitat and reducing water quality. One way to assess habitat under low flows is to use hydraulic models, however, this is problematic because the upper Ovens River has a porous riverbed, meaning that a portion of the flow passes through the riverbed, a type of flow not easily accounted for by hydraulic models.
To better understand the upper Ovens River under very low flows, the North East CMA and Jacobs Group Australia completed a bathymetric and aquatic habitat survey. Jacobs developed an innovative kayak mounted survey rig to complete a high accuracy depth and aquatic habitat survey of 40 km of the Ovens River between Bright and Myrtleford under extreme low flows. The output was an interactive, GIS based map of the river, incorporating the depth survey, spatially oriented photography of the river and quantitatively based conceptual models of the main riffles identified in the river. The interactive map and conceptual models provide the CMA with a powerful tool to understand the river and to determine how habitat availability and condition change as flows reduce.