Your search found 5 records
1 Werner, A. D.; Dang, L. D. 2013. Three-dimensional seawater intrusion modelling of Uley South Basin, South Australia. In Wetzelhuetter, C. (Ed.). Groundwater in the coastal zones of Asia-Pacific. Dordrecht, Netherlands: Springer. pp.177-203. (Coastal Research Library Volume 7)
Groundwater ; Salt water intrusion ; Models ; Calibration ; Aquifers ; Water supply ; Water levels ; Pumping ; Wells ; River basins ; Climate change / Australia / Uley Basin / Eyre Peninsula
(Location: IWMI HQ Call no: 551.457 G570 WET Record No: H046333)
Groundwater in the Uley South basin is a vital source of water supply in the Eyre Peninsula, providing approximately 70 % of the region’s reticulated water. The groundwater resources are at risk of seawater intrusion given that the aquifer is in direct contact with the sea, and that a general lowering of hydraulic heads has occurred over the past two decades. Seawater intrusion has not been investigated thoroughly in Uley South basin; a similar situation for many of Australia’s coastal aquifers. This study develops a three-dimensional seawater intrusion model of Uley South basin using the code MODHMS. The modelling simulates for the first time the current extent of seawater in the aquifer, the temporal salinity variability, and the susceptibility of the aquifer to seawater intrusion, and as such, the model is a significant step forward beyond previous modelling attempts, providing important insights into salinity distributions and salinity mobility. While it is limited by the available information at the time, comparisons with alternative attempts at salinity measurements (e.g. an AEM survey) show a relatively close match between simulated and observed salinities; an encouraging result given well-documented uncertainties in seawater intrusion modelling. Simulations explore the effects of alternative pumping regimes, reduced recharge, and seasonality and other temporal variability effects on seawater intrusion that cannot be assessed using other methods. The impacts of pumping and recharge changes under climate variability are distinguished; both forms of aquifer stress potentially impact on heads and salinities to somewhat similar extents. The ability of the system to recover from long-term pumping is also assessed. At the basin scale, historical changes in the position of the freshwater-seawater interface are mostly localised due to the shape of the aquifer near the coastline (i.e. basement sloping towards the sea). However, the model predicts that some near-coastal piezometers may show increasing salinity trends in the future if current pumping practices continue, and in particular if recharge diminishes under climate change. A comparison between highly dynamic and averaged-stress conditions demonstrates that seasonality is a minor controlling factor in seawater intrusion trends. Aquifer recovery times exceed the periods during which the pumping stresses that induce seawater intrusion are applied. This occurs because cycles of pumping and recovery widen the transition zone between freshwater and seawater, and a large mass of salt remains in the aquifer even after an extensive recovery period.
2 Morgan, L. K.; Werner, A. D.; Morris, M. J.; Teubner, M. D. 2013. Application of a rapid-assessment method for seawater intrusion vulnerability: Willunga Basin, South Australia. In Wetzelhuetter, C. (Ed.). Groundwater in the coastal zones of Asia-Pacific. Dordrecht, Netherlands: Springer. pp.205-225. (Coastal Research Library Volume 7)
Salt water intrusion ; Water quality ; Water security ; Water levels ; Coastal area ; Aquifers ; Sea level ; Irrigated farming ; Hydrogeology ; Indicators / Australia / Willunga Basin
(Location: IWMI HQ Call no: 551.457 G570 WET Record No: H046334)
Seawater intrusion (SWI) causes degradation of water quality and loss of water security in coastal aquifers. Although the threat of SWI has been reported in all of the Australian states and the Northern Territory, comprehensive investigations of SWI are relatively uncommon because SWI is a complex process that can be difficult and expensive to characterise. The current study involves the application of a first-order method developed recently by Werner et al. (Ground Water 50(1):48–58, 2012) for rapidly assessing SWI vulnerability. The method improves on previous approaches for the rapid assessment of large-scale SWI vulnerability, because it is theoretically based and requires limited data, although it has not been widely applied. In this study, the Werner et al. (Ground Water 50(1):48–58, 2012) method is applied to the Willunga Basin, South Australia to explore SWI vulnerability arising from extraction, recharge change and sea-level rise (SLR). The Willunga Basin is a multi-aquifer system comprising the unconfined Quaternary (Qa) aquifer, confined Port Willunga Formation (PWF) aquifer and confined Maslin Sands (MS) aquifer. Groundwater is extracted from the PWF and MS aquifers for irrigated agriculture. In the Qa aquifer, the extent of SWI under current conditions was found to be small and SWI vulnerability, in general, was relatively low. For the PWF, SWI extent was found to be large and SWI is likely to be active due to change in heads since pre-development. Anecdotal evidence from recent drilling in the PWF suggests a seawater wedge at least 2 km from the coast. A relatively high vulnerability to future stresses was determined for the PWF, with key SWI drivers being SLR (under head-controlled conditions, which occur when pumping controls aquifer heads) and changes in flows at the inland boundary (as might occur if extraction increases). The MS aquifer was found to be highly vulnerable because it has unstable interface conditions, with active SWI likely. Limitations of the vulnerability indicators method, associated with the sharp-interface and steady-state assumptions, are addressed using numerical modelling to explore transient, dispersive SWI caused by SLR of 0.88 m. Both instantaneous and gradual (linear rise over 90 years) SLR impacts are evaluated for the Qa and PWF aquifers. A maximum change in wedge toe of 50 m occurred within 40 years (for instantaneous SLR) and 100 years (for gradual SLR) in the Qa. In the PWF, change in wedge toe was about 410 and 230 m after 100 years, for instantaneous and gradual SLR, respectively. Steady state had not been reached after 450 years in the PWF. Analysis of SLR in the MS was not possible due to unstable interface conditions. In general, results of this study highlight the need for further detailed investigation of SWI in the PWF and MS aquifers. Establishing the extent of SWI under current conditions is the main priority for both the PWF and MS aquifers. An important element of this involves research into the offshore extent of these aquifers. Further, predictions of SWI in the PWF should consider future extraction and SLR scenarios in the first instance. A field-based investigation of the Willunga aquifer is ongoing, and the current study provides guidance for well installation and for future data collection.
3 Laattoe, T.; Werner, A. D.; Simmons, C. T. 2013. Seawater intrusion under current sea-level rise: processes accompanying coastline transgression. In Wetzelhuetter, C. (Ed.). Groundwater in the coastal zones of Asia-Pacific. Dordrecht, Netherlands: Springer. pp.295-313. (Coastal Research Library Volume 7)
(Location: IWMI HQ Call no: 551.457 G570 WET Record No: H046338)
The freshwater resources of coastal aquifers are vulnerable to seawater intrusion (SWI) caused by the current rising trends in sea levels, amongst other factors. Recent studies have examined the extents, rates and timescales associated with SWI induced by expected levels of sea-level rise (SLR), but have neglected the effects of transgression (i.e. inland migration of the shoreline in response to SLR). In this chapter, variable-density numerical modelling is used to examine the implications of transgression for a range of SWI scenarios based on simplified coastal aquifer settings. Vertical intrusion during transgressions can involve density-driven convective processes, causing substantially larger amounts of seawater to enter the aquifer and creating more extensive intrusion than that of horizontal SWI occurring in the absence of transgression. Interestingly, cases of transgression where no vertical mixing occurs involve reduced landward migration of the wedge toe, relative to otherwise similar situations without transgression. The rates and extents of SWI caused by transgression and associated vertical mixing appear to be almost non-responsive to the choice of landward boundary condition, contradictory to the findings of SLR-SWI studies that neglect transgression. The findings of this study suggest that modelling analyses that neglect the effects of transgression in SLR-SWI investigations may underestimate significantly the rates and extent of SWI.
4 Knowling, M. J.; Werner, A. D.. 2016. Estimability of recharge through groundwater model calibration: insights from a field-scale steady-state example. Journal of Hydrology, 540:973-987. [doi: https://doi.org/10.1016/j.jhydrol.2016.07.003]
Groundwater recharge ; Models ; Calibration ; Estimation ; Hydraulic conductivity ; Aquifers ; Pumping ; Coastal area ; Spatial distribution ; Discharges / South Australia / Uley Basin
(Location: IWMI HQ Call no: e-copy only Record No: H047639)
(2.66 MB)
The ability of groundwater models to inform recharge through calibration is hampered by the correlation between recharge and aquifer parameters such as hydraulic conductivity (K), and the insufficient information content of observation datasets. These factors collectively result in non-uniqueness of parameter estimates. Previous studies that jointly estimate spatially distributed recharge and hydraulic parameters are limited to synthetic test cases and/or do not evaluate the effect of non-uniqueness. The extent to which recharge can be informed by calibration is largely unknown for practical situations, in which complexities such as parameter heterogeneities are inherent. In this study, a systematic investigation of recharge, inferred through model calibration, is undertaken using a series of numerical experiments that include varying degrees of hydraulic parameter information. The analysis involves the use of a synthetic reality, based on a regional-scale, highly parameterised, steady-state groundwater model of Uley South Basin, South Australia. Parameter identifiability is assessed to evaluate the ability of parameters to be estimated uniquely. Results show that a reasonable inference of recharge (average recharge error 100 K values across the 129 km2 study area). The introduction of pumping data into the calibration reduces error in both the average recharge and its spatial variability, whereas submarine groundwater discharge (as a calibration target) reduces average recharge error only. Nonetheless, the estimation of steady-state recharge through inverse modelling may be impractical for real-world settings, limited by the need for unrealistic amounts of hydraulic parameter and groundwater level data. This study provides a useful benchmark for evaluating the extent to which field-scale groundwater models can be used to inform recharge subject to practical data-availability limitations.
5 Maskooni, E. K.; Werner, A. D.; Solorzano-Rivas, S. C. 2024. Groundwater modelling reports fail to comply with guideline recommendations for model reproducibility. Journal of Environmental Management, 355:120292. [doi: https://doi.org/10.1016/j.jenvman.2024.120292]
Groundwater ; Modelling ; Water policies ; Water management ; Hydrogeology ; Industry ; Best practices ; Decision making ; Stakeholders ; Uncertainty ; Evapotranspiration
(Location: IWMI HQ Call no: e-copy only Record No: H052820)
https://www.sciencedirect.com/science/article/pii/S0301479724002780/pdfft?md5=98cb671e3d72ee7753eea0761da72453&pid=1-s2.0-S0301479724002780-main.pdf
https://vlibrary.iwmi.org/pdf/H052820.pdf
https://vlibrary.iwmi.org/pdf/H052820.pdf
(2.07 MB) (2.07 MB)
Computer models are routinely used to underpin critical decision-making for projects that impact groundwater systems. Modelling results are communicated through technical reports, which advise regulators and other stakeholders of groundwater impacts, thereby informing approvals, project restrictions and monitoring requirements. Several guidelines and texts are available to instruct groundwater model development and reporting. In seven of the eight guidelines/texts reviewed, it is recommended that modelling reports (or a model archive) contain sufficient information for an external party to rebuild the model. This study examined that expectation (assumed to be “best practice”) by reviewing 25 groundwater modelling reports from eight countries and assessing whether the information contained therein was sufficient (or an archive was provided) to rebuild the model on which the report was based. The reports were characterised based on 18 model components (e.g., aquifer properties, boundary conditions, etc.), and the availability of sufficient information in the report to rebuild each one. The “rebuildability” of model components was classified as: (a) reproducible (from the report), (b) reproducible but assumptions needed, and (c) not reproducible. The Analytical Hierarchical Process was employed to rank the reports based on the reproducibility of the models they describe. Only one of the 25 reports provided adequate information to rebuild the model, while one other report was accompanied by a model archive, resulting in two cases of model reproducibility, contrary to guideline recommendations. This outcome reflects problems with reproducibility in the wider scientific community. We conclude that modelling reports need to provide more detailed information to be compliant with best practice or model archives ought to be made available. Addressing this issue will ensure that stakeholders have access to the information needed to properly assess whether future groundwater impacts have been reliably evaluated.
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