2.1.5.3 Gaps

A range of different methods are available to estimate the baseflow component of streams, as it is not something that is easy to measure directly. Estimates of baseflow can help to constrain the groundwater model, but the estimates themselves can be highly variable. Local scale estimates of groundwater contributions to streamflow are sometimes reported in mine environmental impact statements, but these were not actively sought during the project. Local-scale data are of little value for parameterising the regional-scale groundwater model, but may be of use in constraining model results locally by training the groundwater model emulators on the local data. While a high baseflow index was adopted to constrain groundwater model results across the Hunter subregion (see companion product 2.6.2 for the Hunter subregion (Herron et al., 2018)), training of the model emulators on local information may lead to local improvements in model predictions.

Lack of surface water – groundwater interactions data are not a major gap for modelling purposes, as the focus of the modelling is on evaluating the difference between two futures using a probabilistic approach, not on building a deterministic model calibrated to historical data. The groundwater model generates baseflow volumes for input into the river model. This is the major interaction between surface water and groundwater.