2.1.5.1 Observed data

Regional-scale coverage of surface water – groundwater flux data are generally lacking, although there are local studies that have attempted to quantify these fluxes (Heritage Computing Pty Ltd, 2012; Worley Parsons, 2009). For regional-scale modelling, local-scale data can be useful for defining the variability in surface water – groundwater connections across the subregion and putting some upper and lower bounds on the groundwater contribution to streamflow (expressed as a proportion of total streamflow, or baseflow index; see also Kellett et al., 1989). In the EPA (2013) salinity assessment of the Hunter River basin, it was concluded that ‘the detailed interaction between groundwater and surface water in many parts of the Hunter River catchment still requires further research’.

No observed datasets that specifically represent surface water – groundwater interactions have been used as inputs into the hydrological modelling of the Hunter subregion because this is a variable calculated by the model, nor have they been used to constrain model results. Instead a range of common approaches to estimating the groundwater contribution to streamflow are used to determine possible ranges, including extrapolation from local-scale information reported in a mine environmental impact statement (EIS; Section 2.1.5.2).