Oral Presentation NCGRT/IAH Australasian Groundwater Conference 2019

Streamflow generation mechanisms for an intermittent-ephemeral catchment in South Australia: a modelling approach (310)

Karina Y. Gutierrez-Jurado 1 , Margaret Shanafield 1 , Daniel Partington 1
  1. Flinders University, Bedford Park, SA, Australia

In Australia, Intermittent Rivers and Ephemeral Streams (IRES) are the common features that dominate the landscape. Contributing with roughly 70% of the stream network, IRES are key for ecosystems health, are important for farming and agriculture and represent a main source of groundwater recharge. However, the understanding of streamflow generation mechanisms for IRES remains a challenge. This study examines an intermittent-ephemeral catchment in South Australia where little is scientifically known about the processes leading to streamflow generation and the contributing mechanisms, although there are many well-developed hypotheses among the local vineyard owners. Previous research in the catchment has shown complex spatiotemporal interactions between the creek and the shallow aquifer, outlining changes in losing and gaining conditions along the creek during the intermittent flow season. We used a fully integrated surface-subsurface hydrological model coupled with the hydraulic mixing-cell method to investigate the processes leading to the onset of flow for the intermittent season and to determine the spatiotemporal variability of the streamflow generation mechanisms. For this, we analyzed the development of flow generating areas and the dominant contributing flow generation mechanisms at different locations along the catchment at the onset of flow, and during the transition from ephemeral to intermittent flow. The expected results from this study will allow us to better understand streamflow generation at the threshold of flow and at the transition from ephemeral to intermittent flow for an intermittent-ephemeral creek in South Australia. This will be useful to aid IRES management decisions such as those pertaining to ecosystems health monitoring, the vulnerability of the catchment to the effects of droughts, and potential impacts of declines to the shallow groundwater system.