2.7.4 'Non-floodplain or upland riverine' landscape group


The ‘Non-floodplain or upland riverine’ landscape group comprises ecosystems that tend to be in elevated portions of the catchment and includes a diverse range of aquatic and terrestrial ecosystems. The upland riverine landscape classes make up approximately 64% of riverine classes in the Namoi assessment extent, while the upland terrestrial landscape classes make up approximately 10% of this extent.

The majority of the riverine classes within the ‘Non-floodplain or upland riverine’ group in the zone of potential hydrological change are classified as ‘Temporary upland stream’ (745.1 km), reflecting the intermittent or ephemeral nature of many of the stream segments. The remainder of the stream network is classified as ‘Permanent upland stream’ (92.6 km), ‘Temporary upland stream groundwater-dependent ecosystem (GDE)’ (34.7 km) and ‘Permanent upland stream GDE’ (14.2 km). The majority of the non-riverine landscape in the ‘Non-floodplain or upland riverine’ landscape group in the zone of potential hydrological change is classified as ‘Grassy woodland GDE’ (72.8 km2). This landscape class represents a relatively diverse set of vegetation communities that occupy several different landforms with groundwater contributions from potentially different flow paths and hydrogeology. The ‘Upland riparian GDE’ class makes up a very small area of the zone of potential hydrological change (2.9 km2) along with a small area of ‘Non-floodplain wetland’ (13.1 km2) and ‘Non‑floodplain wetland GDE’ (8.1 km2) landscape classes.

Three different components of the ‘Non-floodplain or upland riverine’ landscape group were considered for the qualitative modelling. The upland riverine model included all upland riverine classes and the adjacent riparian vegetation (‘Upland riparian forest GDE’ landscape class). Three receptor impact models were formulated based on this qualitative model: upland riverine (two separate models) and upland riparian forest. Cease-to-flow attributes of the surface water regime were assigned as hydrological response variables for the upland riverine model and the receptor impact variables included changes in macroinvertebrate assemblages and the probability of the presence of tadpoles. For upland riparian forest, groundwater drawdown and overbank flow events were considered the key hydrological response variables. The potential ecosystem impacts on this landscape class were quantified using projected foliage cover. In addition to the upland riverine system, a qualitative model was developed for the non-floodplain wetlands in this landscape group.

Receptor impact modelling indicates that foliage cover during the reference period is an important predictor of foliage cover in the future, and that the experts’ opinion provides strong evidence for maximum additional drawdown having a negative effect, and the number of events having a positive effect on average projected foliage cover. Receptor impact modelling also strongly supports the hypothesis that an increase in the mean number of zero‑flow days and/or the mean maximum length of zero-flow spells will have a negative effect on probability of the presence of tadpoles and on the number of families of macroinvertebrates, despite the experts being quite uncertain about average values.

Last updated:
6 December 2018
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