The knowledge gaps described in this section relate to limited surface water quality and quantity data that lead to limited modelling ability of surface water processes (see companion product 2.6.1 for the Namoi subregion (Aryal et al., 2018b)). Currently there are no streamflow and water quality gauging stations in any of the lower order streams, thus limiting the ability to model the streamflow and water quality of these streams. Some water quality measuring stations exist in the major rivers and tributaries for limited monitoring of nutrient, electrical conductivities and other constituents, however they do not measure dissolved oxygen and pH, which are critical to the survival of most aquatic species.

There is a lack of understanding of the interaction between the surface water and groundwater systems, particularly at the local level. Important knowledge gaps in this area are:

  • quantification of the hydraulic connection between the shallow alluvial aquifers, the GAB and underlying geological basins. While there may be areas of connectivity between basins and between surface and groundwater, the rates of groundwater exchange remain poorly understood on a regional scale
  • controlling mechanisms for vertical leakage (cross-formational flow) for the multiple layers of aquifers and aquitards present in the Namoi subregion. Understanding these mechanisms is critical for determining interaction between groundwater systems and also the effect of depressurisation proposed for CSG developments in the region. Permeability and specific storage can now be measured in situ and these additional data would assist in constraining conceptual and numerical models
  • hydraulic properties of aquitards and response to changes in groundwater pressure within adjacent aquifers. Where several layers of aquifers and aquitards are present, pressure changes caused by groundwater extraction will propagate at various rates in various directions, depending on the physical properties unique to each aquifer and aquitard layer (CSIRO, 2012)
  • groundwater flow fluxes and compartmentalisation of deep aquifers in the Gunnedah Basin
  • influence of geological structures (e.g. the Boggabri Fault, sub-basins, major faults) on regional groundwater flow in the Gunnedah Basin and the extent of compartmentalisation of the aquifers and groundwater flow systems
  • extent of hydrologic connectivity between the alluvial aquifers and the deeper groundwater flow systems in the Gunnedah Basin
  • magnitude of variability in surface water – groundwater connectivity
  • variability of baseflow for the (mostly ungauged) rivers in the Namoi subregion.
Last updated:
6 December 2018