Executive summary
The observations analysis, statistical analysis and interpolation product for the Namoi subregion in the Northern Inland Catchments bioregion describes the information necessary to better understand and model the hydrology of the areas where coal resource development is possible. This provides a quantitative understanding of the Namoi subregion by analysing the observed data and, where required, estimating additional data for locations where data are sparse.
The product presents the following datasets and analyses:
- geography: geographical datasets were used for hydrological and other modelling in the Namoi subregion. Descriptions of input climate data are also provided. Spatial analyses specific to the Namoi subregion were undertaken for some of the meteorological datasets to characterise errors.
- geology: an existing three-dimensional model was adapted for the Namoi subregion to define regional-scale geology for modelling impacts of coal resource development on water-dependent assets. This model is an interpretation of the subsurface geology and structure of the Gunnedah and Surat basins. The interpretation is based on petroleum and coal exploration wells, geological maps and ancillary datasets such as digital elevation models.
- hydrogeology and groundwater quality: relevant hydrogeological datasets, sourced from NSW state agencies, and groundwater models developed for the Namoi river basin in previous studies were used to prepare a hydrogeological assessment for the Namoi subregion. There are two major aquifer systems in the Namoi subregion – the Pilliga Sandstone aquifer and the Namoi Alluvial aquifer, which contains high quality groundwater that is used for irrigation, water supply and stock and domestic use.
- surface water hydrology and water quality: there are 37 gauging stations in the Namoi subregion, with available streamflow data lengths ranging from 14 to 121 years. The median data length is 47.5 years.
- surface water – groundwater interactions: the connectivity assessment demonstrated increasingly widespread regions of disconnection between the aquifer and river systems.
This product includes an assessment of data errors and uncertainties; the spatial and temporal resolution of observations over space and time; and algorithms used in the development of derived datasets. Data gaps are identified.
In addition, this product summarises information about water management for coal resource developments, which is required for numerical modelling of surface water and groundwater.
Relationship to other products
This product on observations analysis, statistical analysis and interpolation is part of a series of model-data analysis products (Component 2), which describe the hydrological relationships between coal resource development and potentially impacted water resources and water-dependent assets in the subregion. This product informs impact and risk analysis (Component 3 and 4) products on the risks to and potential impacts on water resources and water-dependent assets, such as bores and habitats.
