Poster Presentation NCGRT/IAH Australasian Groundwater Conference 2019

1D groundwater elevation prediction model (371)

Stefan S.C. Charteris 1
  1. GHD, Sydney, NSW, Australia

Predicting groundwater elevations based on limited data is often required as part of informing design and impact assessments and represents an ongoing challenge for groundwater specialists. As part of understanding the potential for impacted groundwater levels rising and intersecting a stormwater drain flowing into surface water a 1D groundwater elevation model was developed. The groundwater level model was developed in excel and based on a simple box model with groundwater level in the box increasing with rainfall and net storage decreasing with no rainfall. The representative equation inputs where varied to simulate a two-month groundwater elevation dataset that had a number of significant rainfall events. There was a high degree of fit between simulated and actual groundwater elevations. Due to the high degree of fit, the model was then able to be used to predict groundwater changes over a long term rainfall dataset. Uncertainty analysis was completed by stressing the recharge component to higher and lower levels and then re-calibrating the model while maintaining a high degree of fit. The model relied on simulating response rather than a rigid set of hydrogeological input parameters (storage and hydraulic conductivity) providing more freedom in the variability of input parameters to achieve a fit. Its certainty therefore relies entirely on the goodness of fit. This model was based on groundwater response in a shallow unconfined and unconsolidated aquifer. Further testing is required to validate the model for use on other lithologies and aquifer types, however, it would have direct applicability for a range of assessments where understanding reasonable worst case groundwater elevations using short-term high frequency groundwater elevations is required.