Internal Report 519
Supervising Scientist Division
Department of the Environment, Water, Heritage and the Arts, 2007
About the report
The Tropical Rivers Inventory and Assessment Project is aiming to categorise the ecological character of rivers throughout Australia’s wet-dry tropical rivers region. As part of this project, a preliminary analysis of the flow characteristics of streams within this mostly undisturbed, and relatively data-limited, region was conducted, which could later be used to assess the impacts of potential development.
In general, the tropical rivers region experiences a distinct wet season from October to April, and a dry season for the remainder of the year. Stream flow, as a consequence, is highly seasonal. Long-term discharge records of streams within three relatively well-gauged catchments – Daly (NT), Fitzroy (WA) and Flinders (Qld) rivers – have been analysed to group streams into flow regime units. Hydrological variables based on flow variability, flood regime and intermittency, were derived for the complete record of each stream. Cluster analysis indicated that streams could be grouped broadly into four flow regime groups: (1) perennial, (2) seasonal, (3) dry seasonal, and (4) seasonal-intermittent streams. The coefficient of variation of total annual flow and the mean number of zero flow days were the two most significant variables for classifying streams into flow units.