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Groundwater Resources Vulnerability in a
122 | P a g e However, recent rainfall 2010-2018 is around 80-85% of long-term average rainfall and the decline in rainfall since 1990 is consistent with a 2030 dry scenario rainfall trend determined from climate models. The reduction in rainfall has resulted is a significant tapering or even reversal of increasing hydrograph trends.
We present analyses of hydrographs of over 70 long term monitoring bores installed in the 1960s and 1970s. Estimates of pre-clearing recharge using the chloride mass- balance method are made based on chloride concentrations in groundwater and chloride deposition in rainfall (Leany et al. 2011). Additional recharge since land clearing took place is assessed using the hydrograph method (Healy and Cook, 2002). Daily recharge rates are then modelled with the 1D water balance model U3M-1D Class (Vaze et al. 2005) based on unsaturated flow Richards
equation. Historical rainfall and reference FAO56 evapotranspiration (EVT) (Allen et al. 1998) from interpolated SILO (Queensland government 2018) data along with soil parameters, rooting depth profiles and leaf area index for the crop growing season are key model parameters. The 1D recharge model is calibrated and verified over different portions of observed hydrographs. Simulations with the calibrated 1D recharge model estimate future recharge for future wet, median and dry future scenarios based on climate model data.
A useful result from the recharge modelling is estimation of the rainfall recharge relationship which shows approximately that a threshold amount of annual rainfall of around 300mm is required before any significant recharge in any particular year. The modelling also highlighted the importance of the timing of rainfall to generate deep infiltration and recharge especially at the end of the winter rainfall season when the soil profile is saturated. Long term dry climate scenarios indicate large reductions in the amount of recharge which significantly impacts the long-term sustainable yield of groundwater resources.
1. Allen RG, Pereira LS, Raes D and Smith M, 1998, Crop evapotranspiration – Guidelines for computing crop water requirements, FAO Irrigation and drainage paper 56, Food and Agriculture Organization of the United Nations, Rome, available from:
http://www.fao.org/docrep/X0490E/x0490e00.htm
2. Allison GB and Hughes MW, 1978, The use of environmental chloride and tritium to estimate total recharge to an unconfined aquifer, Australian Journal of Soil Research, 16:
pg. 181-195
3. Healy, R.W., and Cook, P.G. 2002, Using groundwater levels to estimate recharge, Hydrogeology Journal, Volume 10, p. 91-109
4. Leaney F, Crosbie R, O'Grady A., Jolly I, Gow L, Davies P, Wilford J and Kilgour P 2011, Recharge and discharge estimation in data poor areas: Scientific reference guide, CSIRO:
Water for a Healthy Country National Research Flagship, Canberra
5. Vaze j, Teng J and Tuteja NK 2005, CLASS U3m-id: Unsaturated Moisture Movement Model – User Guide, Cooperative Research Centre for Catchment Hydrology, Clayton, Victoria
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A 35 ka record of groundwater recharge using stable water isotopes for Perth Basin in south-west Australia
Stacey C. Priestley 1 , Karina T. Meredith 1 , Pauline C. Treble 1 , Dioni I.
Cendón 1 , Alan D. Griffiths 1 , Suzanne E. Hollins 1 , Andy Baker 2 , Jon-Philippe Pigois 3
1. ANSTO, Lucas Heights, NSW, Australia
2. Connected Waters Initiative Research Centre, UNSW Sydney, Kensington, NSW, Australia 3. Department of Water, Perth, WA, Australia
Objectives: As most large groundwater basins can contain ‘old’ groundwater where extraction exceeds groundwater recharge, knowledge of the past conditions and timing under which groundwater was recharged is needed to sustainably manage groundwater resources. Moreover, the isotopic composition of groundwater can be a useful indicator of rainfall isotope compositions and help to determine the drivers and impacts of rainfall and climate change. Applying isotopic tools to groundwater
contained in regional aquifer systems can provide low-resolution information on recharge intensity, recharge source and past climatic conditions for the region.
Design and Methodology: A dataset containing groundwater ages (14CDIC) and stable isotopes of water (δ18O and δ2H) from two regional groundwater systems within the Perth Basin, the Leederville Formation and Yarragadee Formation, were compiled to create a low-resolution palaeo-archive of groundwater recharge.
Original data and results: The trends in stable isotopes of water over time in the regional groundwater data are consistent with groundwater flow line data supporting our hypothesis that groundwater stable isotopes are a proxy for palaeo-recharge.
A comparison between modern groundwater and rainfall water isotopes indicates that recharge is biased to months with high volume and/or intense rainfall from the westerly wind circulation and that this has been the case for the last 35 ka. Lower stable water isotope values are interpreted to represent recharge from higher volume and/or more intense rainfall from 35 ka through the Last Glacial Maximum period although potentially modulated by changes in recharge thresholds.
Conclusion: The groundwater isotope record is interpreted to be a low-resolution archive of recharge driven by changes in the relative intensity of past rainfall and recharge thresholds. This long-term stable isotopic recharge record provides a greater understanding of groundwater palaeo-recharge, and the connection between recharge and climate in the past.
Port Phillip Bay - the real value
Derek J. Walters 1 , Peter Dahlhaus 1
1. Centre for eResearch and Digital Innovation, Ballarat, VIC, Australia
Changing climates and higher sea levels are affecting all coastlines globally, and with over 85% of Australians living within 50km of the coast, this is a pressing national issue (Clark & Johnson 2017). In Victoria, rising sea levels are affecting Port Phillip Bay in many ways, one of which is altering the services provided by groundwater systems (SRW 2014). While there have been numerous investigations into the groundwater and geology of Port Phillip Bay (Phillipson 2010; Dahlhaus et al 2004;
Leonard 1992), this PhD research project focuses on conceptualizing the hydro geological systems and groundwater flows into Port Phillip Bay and the services they
124 | P a g e provide. The investigation takes a holistic view, based on the beneficial uses defined in the State Environmental Protection Policy (waters) guidelines, and the Victorian Water Plan set out by the Victorian Government (EPA 2018). The conceptual models will identify economic, environmental, social and cultural values of the groundwater along the coastline of Port Phillip Bay, linking them to flow paths, the coastal
Ghyben-Herzberg relation, recharge and discharge, and water quality. These conceptualizations will be used to predict how groundwater services might respond to modelled climate change and sea level rise as defined by the Intergovernmental Panel on Climate Change Fifth Assessment report (IPCC 2014). A much larger study, led by CSIRO, will use this information in development of high-resolution climate and hydrodynamic models as well as inundation and coastal erosion models. Creation of hydro geological conceptual models, together with the CSIRO models, will contribute to better managing the impacts of rising sea levels to Port Phillip Bay coastline. The values identified and investigated through this research project highlight the holistic values of groundwater, rather than the traditional view that solely focuses on the economic value of groundwater extraction.
1. Clark GF & Johnston EL (2017). Australia state of the environment 2016: coasts, independent report to the Australian Government Minister for Environment and Energy, Australian Government Department of the Environment and Energy, Canberra. retrieved 6/6/2019 from: https://soe.environment.gov.au/sites/default/files/soe2016-coasts-launch- 17feb.pdf?v=1488793015
2. SRW (2014). Port Phillip and Western Port Groundwater Atlas. Maffra, Victoria, Southern Rural Water: 68. Retrieved 6/6/2019 from: http://www.srw.com.au/wp-
content/uploads/2016/03/Port-Phillip-GW-Atlas-Complete-Web.pdf
3. Phillipson, K. (2010). Port Phillip CMA Groundwater Flow Modelling Report. Melbourne, Victoria, Victorian Government Department of Sustainability and Environment: 433.
4. Dahlhaus, P. G., D. S. Heislers, D. Brewin, J. G. Leonard, P. R. Dyson and D. P. Cherry (2004). Port Phillip and Westernport Groundwater Flow Systems. Melbourne, Victoria, Port Phillip and Westernport Catchment Management Authority: 90.
5. Leonard, J. G. (1992). Port Phillip Region Groundwater Resources - Future Use and Management. Melbourne, Department of Water Resources, Victoria.
6. EPA (2018). State Environment Protection Policy (Waters of Victoria). Erratum. Southbank, Victoria, EPA Victoria. Publication S 499: 86. Retrieved 6/6/2019 from:
http://www.gazette.vic.gov.au/gazette/Gazettes2018/GG2018S499.pdf
7. IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp. Retrieved 6/6/2019 from: https://www.ipcc.ch/report/ar5/syr/
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Groundwater availability and climate change - assessing the combined influence of reduced water availability and increasing demand on the Barwon Downs groundwater resource
Louise Lennon 1 , Brian Barnett 1 1. Jacobs, Melbourne, VIC, Australia
Climate change has the potential to reduce future groundwater and surface water availability at times when demand will be increasing. The combined influence of less water availability and increase demand was considered for the future operation of the Barwon Downs borefield in south west Victoria. The Barwon Down’s borefield is an important drought supply for the region and supplied up to 70% of Geelong’s water during the Millenium Drought. The aquifer is primarily recharged from infiltration of rainfall in outcrop areas.
To support the licence renewal of the Barwon Downs borefield, the influence of climate change on demand forecasts and recharge to the aquifer were
considered. As part of the numerical modelling assessment, a number of predictive modelling scenarios were used to address future climate change. The assessment initially involved implementation of DEWLP Guidelines on future climate change to determine appropriate changes to groundwater recharge. A total of four climate change scenarios were considered in accordance with the Guidelines. Initial model results suggested that the predicted impacts were not particularly sensitive to the changed recharge condition. This reflects the fact that future groundwater extraction is sustained through changes in water stored in the aquifer and by changes in
groundwater discharged at the surface.
Subsequent simulations included the increased future groundwater extraction that would be required to sustain the increased water demand under future climate
change. The combined influence of increased demand and reduced water availability generated significantly greater impacts revealing the true impact of a drier future climate.
Uncertainty analysis in groundwater modelling and its environmental management applications
Mahsa Amirabdollahian 1
1. NSW Department of Industry, Water branch, Parramatta, NSW, Australia
The environmental models are mostly very complicated and virtually unbounded.
This complexity results in uncertain modelling results. The two main sources of uncertainty are model and parameter uncertainty. The available mathematical and numerical groundwater models may not represent the exact natural process in the groundwater aquifers. The material properties are poorly known due to limited number of measurements and the natural high heterogeneity in soil properties.
The groundwater model parameter values are generally estimated using calibration processes using limited number of observations. The real-world systems are highly complex and even large calibration databases can provide multiple estimates of all system parameters which are equally probable. This is called non-uniqueness issue.
There are various methods presented in the literature to quantify the groundwater model uncertainty and/or estimate the reliability/possibility of the outcomes of the
126 | P a g e groundwater model. This paper tests the Iterative Ensemble Smoother (IES) tool in a regional scale real-work groundwater model with hundreds of parameters. The IES is an open-source and model independent tool which was developed to overcome the computational burden associated with matching large database of groundwater history in real-world scale environmental models. IES is a tool to quantify the uncertainty in highly dimensional parameter spaces. This paper explains the
application of IES in real-world groundwater models and its effectively and efficiency to estimate posterior forecast uncertainty when the future projection involves large number of parameters.
The model independent IES is an emerging technology which enables environmental modellers to account for model input uncertainty at realistic spatial and temporal scale. The application of this technology will lead to better forecast uncertainty estimation and improve the usability of environmental models in decision making.
The results of this case study can help environmental managers to select informed decisions by having reliable information about likelihood of environmental
phenomena.
Meeting growing water demands in an uncertain future: a case study of current and future groundwater supply challenges and opportunities for Honiara, Solomon Islands
Shaun Kies-Ryan 1 , Samantha Kies-Ryan 1
1. Earth Water People, Highgate Hill, QLD, Australia
Currently, groundwater bores and springs make up the total water supply source for Honiara. Current demand is starting to overcome supply, with reliance on aging or under-performing assets and spring supply shortages due limited treatment capacity of high turbidity in high rainfall periods. By 2050, water demand is projected to double to around 80 ML/day 1.
The work presented is a situational analysis of current and future challenges, as part of work for the water utility, Solomon Water, on bore field performance and
feasibility studies to secure further groundwater supplies for Honiara in alignment with the utilities 30-year Strategic Plan.
Honiara has two aquifers, the deep confined fractured rock aquifer and the semi- confined alluvial Guadalcanal Plains Aquifer. Much of the conceptual understanding of the aquifers has been developed through old, discontinued, government
programs 2 or via major donor projects on development of Honiara’s water supplies in 1997 and 2013 3,4. To date, the boundaries of the aquifers and inputs and outputs of the system are loosely defined or are not defined. However as is a common challenge in many Pacific nations, monitoring and understanding of the overall capacity of the aquifers has not been adequately funded, leading to incremental and reactionary developments.
In terms of Honiara’s bore water supply, the majority of bores are constructed within the confined fractured rock aquifer, with bore fields spread across the city. Four out of six bore fields are producing less than 65% of their target yields. Ongoing work is showing that the reduced yields are a combination of well interference and screen clogging.
The semi-confined aquifer has not been developed extensively for Honiara’s water supply. Honiara sits on the western edge of the 40 km wide Guadalcanal Plains, which consists of deep unconsolidated sediments (up to 200 m thick) 2. This area has
127 | P a g e potential for further development as indicated by many privately-owned bores already drilled here. Given the current level of monitoring and understanding about Honiara’s groundwater resource, a precautionary approach is required.
Having a broader understanding of groundwater systems can lead to better
responses to these challenges, such as stronger water policy, more effective water sector collaboration and skills capacity building. This in turn will help build climate change resilience in the Solomon Islands.
1. Hunter H2O. 2017. Solomon Water 30-year Strategic Plan. Main Report. February 2017.
2. Lekelalu, I. 1998. Guadalcanal Plains, Solomon Islands, Groundwater Availability Guide.
SOPAC Training Report 77.
3. JICA 1997. Improvement of Water Supply Facilities in Honiara. Japanese International Cooperation Agency.
4. JICA 2013. Improvement of Water Supply and Wastewater Systems for Honiara and Auki.
Japanese International Cooperation Agency.
Seawater intrusion in a warming world
Thuy Nguyen 1 , Xiayang Yu 2 , Pei Xie 2 , Chenming Zhang 1 , Chengji Shen 2 , David Andrew Barry 3 , Ling Li 4
1. University of Queensland, Brisbane, QLD, Australia
2. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, Jiangsu, China
3. Laboratoire de technologie écologique, Institut d’ingénierie de l’environnement, Faculté de l’environnement naturel, architectural et construit, Ecole Polytechnique Fédérale de Lausanne, Laussane, Switzerland
4. School of Engineering, Westlake University, Hangzhou, China
Coastal aquifers are under permanent threat of seawater intrusion (SI), the process of seawater driven landward at the base of the aquifers by variable density flow.
Density contrast between fresh and saline waters, however, does not solely depend on salinity difference as considered in most SI studies but also their temperatures.
Based on survey data, we show that temperature variation of up to 15°C is fairly common between seawater and groundwater in various parts of the global coastline and the difference could be either expanded or shrunk under the warming climate depending on their current situation and their location in the world. Therefore, temperature effects should not be readily neglected. Furthermore, temperature and salinity gradients coexisting alongside each other suggests interesting changes of flow patterns and circulation following double diffusive mechanism. Using results from laboratory experiments and numerical simulations, we figure out that the intrusion process enhances with colder seawater and reduces with warmer seawater.
More importantly, pore-water flow in the saltwater wedge was modified significantly with a second circulation cell formed near seaward boundary and the regular
circulation cell is squeezed into a smaller area with stronger inflow from the beach surface. The thermal impact and coastal vulnerability were then calculated for all coastal areas around the world based on their current temperature contrast and projected future change. The results reveal that a large portion of world coastline is thermally sensitive and vulnerable to changes of land surface and ocean temperature in the warming climate.
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