By Dr Ryan Burrows
Groundwater is not simply a static water source underground as it can interact with surface environments such as streams and rivers. Importantly, groundwater discharge maintains surface water levels in many stream environments, such as pools, during drought conditions.
We investigated how important groundwater was for the plants and animals living in intermittent streams. Streamflow intermittency (i.e. when surface water stops flowing) is currently increasing due to climate change and groundwater extraction. Because of this, there is a pressing need to understand the importance of groundwater inputs for the ecology of intermittent streams, as well as streams that flow all year round.
The growth of algae and aquatic plants (i.e. primary producers) in the intermittent streams we studied was strongly linked to groundwater inputs which sustained wetted environments during dry periods. These primary producers were the main food and energy source for aquatic insects and other animals in our study streams.
Importantly, we also found evidence that inorganic carbon from groundwater was incorporated into the biomass of primary producers and animals. Whether this inorganic carbon from groundwater contributed to the energy of stream life, or simply acted as a tracer, is still to be investigated.
Overall, groundwater discharge to surface aquatic environments can play a critical role for maintaining, and possibly enhancing, important ecological processes and the diverse species assemblages that contribute to local and regional biodiversity.
This research has improved our understanding of potential ecological responses to changes in groundwater-surface water dynamics brought about by human activities such as coal seam gas extraction and coal mining. It has also strengthened regulator and industry understanding of the ecological importance of surface water-groundwater connectivity in intermittent streams. The research outcomes will strengthen the Independent Expert Scientific Committee advice on coal seam gas and mining project proposals that may impact the ecology of intermittent streams.
This research was funded by the Australian Government Department of Environment and Energy and was part of a larger research project titled “Research to inform the assessment of ecohydrological responses to coal seam gas extraction and coal mining”. The report can be found here.
This work appeared ahead of print in Freshwater Science.