Geological permeability controls streamflow generation in a remote, ungauged, semi-arid drainage system

Abstract

Study region: A semi-arid drainage system overlying a thick (12 km) sedimentary sequence on the Dampier Peninsula in northwestern Australia. Study focus: In this study we combine aerial geophysics, geological mapping, hydrometry and hydrochemistry with aerial image analysis and stream mass balance modeling to delineate the key hydrogeological structures and processes that control streamflow generation within a remote ungauged semi-arid watershed. New hydrological insights for the region: Four distinct processes of streamflow generation were identified, each dependent on the spatial distribution of lithological permeability; (1) ephemeral rainfall runoff over low-permeability surface lithologies, (2) intermittent flow generated by seasonal groundwater discharge from the unconfined aquifer above a newly mapped clay layer, (3) persistent flow from contact springs via interbedded high- and low-permeability layers, and (4) perennial flow associated with regional groundwater discharge at headwater springs. This study highlights the importance of geological permeability and the resultant hydrogeological processes as controls on streamflow generation, particularly in low-relief and arid regions where topography is less likely to determine the distribution of streamflow.

Keywords

• Ephemeral stream
• Intermittent river
• Non-perennial streams
• Spring mechanisms
• Surface water - groundwater interaction