Variety is the spice of river life: recognizing hydraulic diversity as a tool for managing flows in regulated rivers

Biodiversity in river ecosystems is supported by physical diversity in the river environment. Physical diversity is, in part, defined by hydraulic characteristics such as water depth, flow velocity, and turbulence. Establishing the relationship between discharge and hydraulic character is an important step in the process of managing flow to maintain and enhance physical and biological diversity within these systems. This paper considers the relationship between discharge and hydraulic character in the regulated lowland section of the River Murray, Australia. Spatial variation in hydraulic conditions was determined by mapping hydraulic character at three flow discharges: 2000, 3000 and 9000 ML day-1 in three reaches of the River Murray. These data were used to define patches of distinct hydraulic conditions, primarily using depth-averaged flow velocity. The physical character and spatial arrangement of these patches varied according to reach and discharge. This study shows that spatial flow variability can be used as a management tool to maximize habitat diversity in regulated rivers.