Landscape Controls on Runoff and Streamflow in Large Arid Zone Catchments

The arid zone catchments of the Lake Eyre Basin (LEB, area of 1.2*10km) in central Australia have unregulated, highly variable flow regimes and contain a paucity of gauging stations. In developing hydrological models of these catchments, only limited gauging station data are available for identifying the broad landscape differences influencing runoff and streamflow. The catchments have been divided into two major landscape units with significantly different hydrological characteristics. These are the “channel/floodplain” and “hillslope” units. The channel/floodplain landscape unit represents the extensive braided channel systems that develop on these very low gradient catchments. Modelling and satellite observations indicate that this unit can be further divided into a primary channel land-type conveying small flows and a floodplain land-type conveying larger flows with a larger storage capacity, but similar routing parameters, to the primary channel land-type. The hillslope landscape unit comprises the remainder of the catchment and the paucity of gauging station data and spatial variability of rainfall limits the scope for further subdivision of this landscape unit. A grid-based, conceptual rainfall-runoff model was developed for a number of large catchments in the LEB. The modelling approach allowed for the incorporation of landscape controls into the model whilst retaining a parsimonious conceptual structure appropriate for the paucity of hydrological data in this region. The modelled catchments ranged in size from 10,000 to 60,000 km and covered a large geographic expanse of the LEB. The simple, consistent classification of landscape units utilized in this study allowed the resulting differences between catchments to be clearly identified, with the differences being related to the landscape controls on hydrological behaviour of the catchments.