The ‘Riverine’ landscape group is dominated by ephemeral streams (63%) with the remainder roughly equally divided between intermittent and perennial streams. Qualitative models were developed for each landscape class, but receptor impact models were only developed for perennial and intermittent streams. Ephemeral streams in this subregion were considered predominantly rainfall dependent and less vulnerable to hydrological changes from coal mining.
The qualitative model for perennial streams is premised on a flow- and habitat-based classification of aquatic macroinvertebrates (i.e. free-swimming macroinvertebrates in pool habitats and fast-water macroinvertebrates in riffle habitats). Groundwater levels, riffle flow, overbench flow, overbank flow and zero-flow days were identified as critical determinants of instream and riparian habitat condition. Reductions in groundwater levels and streamflow, resulting in increases in zero-flow days, are generally considered to have negative impacts on riparian and subsurface habitats. Potential changes in water quality from changes in hydrology are not represented in the model.
Receptor impact models were designed to focus on the response of riffle-breeding frogs and flow-dependent macroinvertebrates (Hydropsychidae larvae) to changes in the number of zero-flow days and duration of zero-flow spells. As the number of zero-flow days increase, experts were of the opinion that:
- the probability of presence of riffle-breeding frogs would drop quite dramatically, with the model reflecting a chance of no presence under extremely dry conditions
- the density of Hydropsychidae larvae would drop dramatically, with the model reflecting the possibility of less than 1 per m2 under increasingly intermittent flow regimes.
A qualitative model for intermittent streams was developed through modifications to the perennial streams model. The model lacks pool-breeding frog species, a group which is instead replaced with non-specialist breeding frogs. The model also lacks perennial flow over riffle substrate as a main driver for success of riffle-breeding frog eggs, flow-dependent macroinvertebrates and fishes preferring fast-water habitats. The same hydrological variables critical to habitat condition in perennial streams are relevant to intermittent stream habitats, with flow reductions and lowering of the watertable generally assumed to result in negative impacts. Again, the potential changes in water quality from changes in hydrology are not represented in the model.
The receptor impact models focus on the response of hyporheic invertebrate taxa to changes in zero-flow days and the duration of zero-flow spells, and the response of riffle-breeding frogs to changes in zero-flow days and the duration of zero-flow spells. As the number of zero-flow days increase, experts consider that:
- mean hyporheic invertebrate taxa richness would fall, with the chance of fewer than 10 in 6 L of water under extremely dry conditions
- the probability of presence of riffle-breeding frogs would drop quite dramatically, with the possibility of no presence under extremely dry conditions.
Product Finalisation date
- 2.7.1 Methods
- 2.7.2 Prioritising landscape classes for receptor impact modelling
- 2.7.3 'Riverine' landscape group
- 2.7.4 'Groundwater-dependent ecosystem' landscape group
- 2.7.5 'Coastal lakes and estuaries' landscape group
- 2.7.6 Limitations and gaps
- Contributors to the Technical Programme
- About this technical product