Abstract

1. The flow regime of a river is well established as being one of the key drivers of riverine ecosystem type, diversity and condition. This is especially true of seasonal rivers that experience a cease to flow period over the dry months of the year. 2. In order to effectively assess changes to the flow regime, it is required that flow data be quantified into metrics for ease of assessment and to effectively relate changes to environmental outcomes. 3. Previous methods have used large numbers of, often complex, flow metrics to assess the flow regime. These metrics are often highly internally correlated with each other which may pose problems when considering how these metrics are assessed. The metrics are also often complicated which introduces issues for communication of results. We suggest that due to high internal correlation between metrics, significantly fewer metrics are required to describe the flow regime, and owing to the high correlation within same season flow metrics, simple metrics can be selected. 4. We report on a series of six flow metrics that cover the whole of the flow regime, that are reported annually and that are simple to assess and interpret. We then apply those six metrics to establish environmental water requirements for the North Para River in the Barossa Valley of South Australia. 5. Environmental water requirements are defined using upper and lower bounds of a moving average for each metric, rather than a defined threshold. We suggest this better reflects the highly variable nature of seasonal rivers, and the subsequent tolerances of the flora and fauna that inhabit them.