[1] A set of water level time series collected along a transect through a sedimentary island aquifer was used to test the utility of various simple models of ocean tidal propagation in bounded one-dimensional aquifers. Fourier spectra were calculated for the ocean tidal modes and compared with spectra measured in wells along the island transect. Other sources of fluctuation could be neglected. An observed spatial bias in the well responses (attenuations and lags) could not be modeled by a homogeneous aquifer theory. A theory involving composite heterogeneity accounted well for the spatial bias, yielding estimates of aquifer transmissivities and storage coefficients indicating a fivefold difference in hydraulic diffusivity along the transect. A lack of well locations toward one end of the transect reduced the statistical significance of this result, with correlations between regression parameters evident. At the same time, a second bias was seen involving the ratio of signal amplitude and lag with penetration distance into the aquifer, as observed in prior tidal studies. A brief set of numerical experiments showed that horizontal layering in aquifer properties was the most probable cause of this propagation bias. Application of these results to the island data set supported a conceptual stratigraphic model of a highly conductive, sloping stratum underlying a less conductive, superficial sand layer. This model is inconsistent with well logs along the island transect but is supported by additional off-transect well logs. It was concluded that one-dimensional tidal propagation models may be useful in inverse characterization of aquifers with macroscale hydrogeological structures, and that the analysis of measured propagation bias has the potential to yield extra information on aquifer properties in the vertical direction.

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Abstract:To meet increasing urban water requirements in a sustainable way, there is a need to diversify future sources of supply and storage. However, to date, there has been a lag in the uptake of managed aquifer recharge (MAR) for diversifying water sources in urban areas. This study draws on examples of the use of MAR as an approach to support sustainable urban water management. Recharged water may be sourced from a variety of sources and in urban centers, MAR provides a means to recycle underutilized urban storm water and treated wastewater to maximize their water resource potential and to minimize any detrimental effects associated with their disposal. The number, diversity and scale of urban MAR projects is growing internationally due to water shortages, fewer available dam sites, high evaporative losses from surface storages, and lower costs compared with alternatives where the conditions are favorable, including water treatment. Water quality improvements during aquifer storage are increasingly being documented at demonstration sites and more recently, full-scale operational urban schemes. This growing body of knowledge allows more confidence in understanding the potential role of aquifers in water treatment for regulators. In urban areas, confined aquifers provide better protection for waters recharged via wells to supplement potable water supplies. However, unconfined aquifers may generally be used for nonpotable purposes to substitute for municipal water supplies and, in some cases, provide adequate protection for recovery as potable water. The barriers to MAR adoption as part of sustainable urban water management include lack of awareness of recent developments and a lack of transparency in costs, but most importantly the often fragmented nature of urban water resources and environmental management.

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Use of Managed Aquifer Recharge (MAR) has rapidly increased in Australia, USA, and Europe in recent years as an efficient means of recycling stormwater or treated sewage effluent for non-potable and indirect potable reuse in urban and rural areas. Yet aquifers have been relied on knowingly for water storage and unwittingly for water treatment for millennia. Hence if 'leading edge' is defined as 'the foremost part of a trend; a vanguard', it would be misleading to claim managed aquifer recharge as a leading edge technology. However it has taken a significant investment in scientific research in recent years to demonstrate the effectiveness of aquifers as sustainable treatment systems to enable managed aquifer recharge to be recognised along side engineered treatment systems in water recycling. It is a 'cross-over' technology that is applicable to water and wastewater treatment and makes use of passive low energy processes to spectacularly reduce the energy requirements for water supply. It is robust within limits, has low cost, is suitable from village to city scale supplies, and offers as yet almost untapped opportunities for producing safe drinking water supplies where they do not yet exist. It will have an increasingly valued role in securing water supplies to sustain cities affected by climate change and population growth. However it is not a universal panacea and relies on the presence of suitable aquifers and sources of water together with effective governance to ensure human health and environment protection and water resources planning and management. This paper describes managed aquifer recharge, illustrates its use in Australia, outlining economics, guidelines and policies, and presents some of the knowledge about aquifer treatment processes that are revealing the latent value of aquifers as urban water infrastructure and provide a driver to improving our understanding of urban hydrogeology.

Australian experience at five research sites where stormwater and reclaimed water have been stored in aquifers prior to reuse, have yielded valuable information about water treatment processes in anaerobic and aerobic aquifers. One of these sites is the stormwater to potable water ASTR project at the City of Salisbury, a demonstration project within the broader EC project 'RECLAIM WATER'. A framework for characterising the effectiveness of such treatment for selected organic chemicals, natural organic matter, and pathogens is being developed for inclusion in new Australian Guidelines for Management of Aquifer Recharge. The combination of pre-treatments (including passive systems such as reed beds) and aquifer treatment effectiveness in relation to source waters and intended uses of recovered water will be described. Advantages and disadvantages of various types of pre-treatments in relation to effectiveness and sustainability of managed aquifer recharge will be discussed taking account of aquifer characteristics. These observations will be consolidated into a draft set of principles to assist in selection of engineered treatments compatible with passive treatment in aquifers.

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27The fate of nine trace organic compounds was evaluated during a 12 month large-28 scale laboratory column experiment. The columns were packed with aquifer sediment 29 and evaluated under natural aerobic and artificial anaerobic geochemical conditions, 30 to assess the potential for natural attenuation of these compounds during aquifer 31 passage associated with managed aquifer recharge (MAR). The nine trace organic 32 compounds were bisphenol A (BPA), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), 33