This subject has been a focus of research in Perth, Western Australia, since 1984-85. During the Perth Urban Water Balance Study, it became apparent that there was no obvious way to incorporate the behaviour of shallow lakes and wetlands into regional scale groundwater flow models of the type needed for the Swan Coastal Plain near Perth.

Following preliminary modelling in vertical section by a final year engineering student at UWA, Oo Gin Hung, during 1985, collaboration with Dr Malcolm Davidson led to solutions that define steady groundwater flow patterns near circular or elliptical lakes in plan, or semi-circular, semi-elliptical or infinitesimally thin lakes in vertical section. The solutions were obtained by a special kind of boundary integral method, where the solutions were expressed in terms of functions that automatically satisfy boundary conditions at boundaries other than the edge of the lake. The work was published by Townley and Davidson (1988).

Simon Nield started his MSc thesis at UWA in 1987. Whereas the work with Malcolm Davidson considered the effects of different aquifer fluxes upgradient and downgradient of a lake, Simon set out to include the effects of recharge. Simon's MSc was completed in 1990. It led to identification of a number of different flow regimes that could be classified as "recharge" (where lake water recharged the aquifer over the whole lake bed), "discharge" (where groundwater discharged into the lake over the whole lake bed) or "flowthrough" (where groundwater discharged into the lake over part of the lake bed and lake water recharged the aquifer over the remainder). A brief paper by Townley et al. (1988) presented the first results.

With assistance from Tony Barr from 1989 to 1993, Simon Nield's results were greatly extended. Tony's work led not only to a comprehensive paper published by Nield et al. (1994), but most importantly to a user-friendly tool called FLOWTHRU, described by Townley et al. (1992). An interactive version of FLOWTHRU is now available online. FLOWTHRU is also available as a standalone package, for PCs and Macs, but care should be taken to ensure that the executable is the latest version, which corresponds perfectly with the definition of flow regimes provided by Nield et al. (1994). If you have or acquire a version that does not seem to correspond 100% with the paper by Nield et al., please make contact to request a revised version.

Dr Michael Trefry undertook most of the detailed analyses leading to extension of steady results to three dimensions. Although the numerical work was completed in about 1993, further analytical work was undertaken in 1996-97, leading to a paper by Trefry and Townley (1998). The 3D results were finally published by Townley and Trefry (2000). Supporting software for particle tracking and preparation for tessellation and rendering has been described by Trefry and Townley (1996).

Numerous field studies have been undertaken over the years to support our understanding of surface water - groundwater interaction. A major study with Dr Jeffrey Turner at CSIRO led to a very large (453-page) report by Townley et al. (1993a), this being summarised as one of a series of six reports on wetlands of the Swan Coastal Plain (Townley et al., 1993b). Much of this work has yet to be published in more accessible literature, but Townley et al. (1991) provided a brief introduction. A study of Perry Lakes, directly across the road from CSIRO's laboratories in Floreat Park, led to another report by Townley et al. (1995); this work has led to extensive field studies by John Rich as part of his PhD research. David Sim undertook an interesting study of Shenton Park Lake for his 1995 Honours thesis in Natural Resource Management at UWA; this study demonstrated the annual cycle from a recharge regime during winter rains, to flowthrough regimes for most of the year, and possibly to a discharge regime when the lake nearly dries in late summer. Several other studies on tailings storage facilities, mine pit lakes and dredge ponds (in mining of mineral sands) have contributed to our understanding, but these reports remain confidential to clients.

Andrew Brooker undertook an Honours thesis in Mathematics at UWA in 1990, developing a boundary integral element method (BIEM) for studying the flow of two fluids with different density through a causeway or levee. This work was motivated by studies of ponds used for solar salt production, in which different ponds contain fluids of different salinity, and there exists the possibility of bi-directional flow through a sufficiently permeable levee. This work led to a paper by Brooker and Townley (1994), describing a flow process which has been observed through in the Great Salt Lake in Utah.

Townley's 1995 comment on a paper by John Wilson on induced infiltration from rivers into aquifers remains one of the few published comments in Water Resources Research to which there was no reply. Further work by Tony Barr on this topic has yet to be published. It involves a detailed explanation of how FLOWTHRU can be used to explain flow patterns beneath rivers and streams when there are pumping wells nearby.

The most recent advances have been made by Dr Anthony (Tony) Smith, who now works with CSIRO Land and Water in Perth. Tony's PhD research focused on computation and visualisation of dynamic groundwater flow patterns beneath shallow lakes and wetlands, in response to periodic forcing. By "periodic", we mean a combination of steady (or average) climatic conditions, and harmonic (or sinusoidal) fluctuations in climate with a particular amplitude and phase. In general, our focus has been on annual or seasonal fluctuations, though the same techniques apply to tidal or diurnal fluctuations. Dynamic animations of streaklines have been prepared by Tony and made available via a standard web browser. One paper has been finished on the influence of regional setting on steady lake-aquifer interaction (Smith and Townley, 2002). Another describes the methods by which periodic fluctations can be visualised (Smith et al.,2005).

The paper by Turner and Townley (2006) was more than 15 years in the making. Most of the work was completed by 1997, so by publishing in 2006 we missed an opportunity to provide new results in a timely fashion. The paper combines modelling and field work carried out by a large team at CSIRO, over many years.