Potentiometric surface - simulated 1970 raster

## **Abstract** 

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied.  

 

The simulated 1970 unconfined potentiometric surface (watertable)  across the entire model domain. The potentiometric surface represents the uppermost saturated surface and variability over the region.  

 

Choosing a year that best represents the climatic circumstances for the simulation objectives is an essential part of the steady-state assessment. This decision was influenced by the availability of appropriate calibration data.  This approach generally allows for the selection of a year that was outside the bounds of a longer term shift in annual rainfall distribution.  The selected steady-state condition was based on 1970 rainfall and assumed no groundwater extractions.  This initial state was selected to represent predevelopment conditions as post-1970 historic groundwater pumping in the region (on and offshore) have not achieved a quasi-equilibrium response as based on available groundwater hydrograph trends.    The transient simulation period was 1970 to 2012.  This period captures both pre-mine development and a range of varying climatic conditions  including above average wet and dry sequences.  The 1970 starting date enables the incorporation of historic groundwater extraction data into the model and provides sufficient lead time for the groundwater model to minimise the impact of initial conditions on model predictions associated with the period of interest  namely the calibration/validation period of 2000 to 2012.   Copied from the Gippsland Groundwater Model report  2015.

## **Purpose** 

The surface indicates the likely regional groundwater flow direction and gradient in the area illustrating the condition at time point 1970.

## **Dataset History** 

The simulated 1970 unconfined potentiometric surface (watertable) and depth-to-watertable across the entire model domain is shown in Figure 114 and Figure 115 respectively.  (ED. see figures in the Gippsland Groundwater model report). Visual comparison of the Victorian SAFE depth to watertable map (Figure 116) with the steady-state simulated depth to watertable shows the watertable surface is reasonable within the alluvial systems  however in some upland locations the watertable appears in greater connection with surface features than presented in the Victorian Aquifer Framework (VAF) data.  This is not considered a significant issue as these areas are well beyond the zone of interest. It must be noted that the VAF depth to watertable map was derived using a combination of terrain analysis and interpolated bore data  and in part on proximity to streams within the exposed basement areas.  Additionally  the VAF reflects the 1990 conditions whereas the simulated steady-state depth to watertable represents pre-development conditions.  As such  it is expected that that the simulated steady-state depth to watertable map would have a greater area of shallow watertable than reported in the VAF spatial layer.  



This text copied from the Gippsland Groundwater Model report 2015. See Beverly et al (2015) for more details.

## **Dataset Citation** 

Bioregional Assessment Programme (2015) Potentiometric surface - simulated 1970 raster. Bioregional Assessment Source Dataset. Viewed 05 October 2018, http://data.bioregionalassessments.gov.au/dataset/883f86cd-8d1c-4672-bcde-7b872248ddb2.

Tags: GEOSCIENCES-Hydrogeology, Gippsland Basin bioregion, Victoria, geoscientificInformation, inlandWaters
Organization: Bioregional Assessment Program