By siting Launceston at the confluence of the Tamar and North and South Esk rivers, Colonel Paterson may have solved his drinking water problem, but he also subjected the city to the 6000-year history of silt accumulation around the head of the Tamar – Inveresk, Glebe flats etc. Are all silt beds built up over those 6000 years.

The hydrodynamic processes of the tidal Tamar Estuary ensure that any silt entering this confluence from the North and South Esk catchments will tend to migrate to the area we now call Home Reach and the Yacht Basin. These natural processes, flocculation and asymmetrical tidal flows, cause the fine particle silt entering the Tamar through the Cataract Gorge, Tailrace, and North Esk to flocculate (form flocs of “mud”) in the mixing zone from Tamar Island to Freshwater Point (where the salt concentration in the marine waters is of sufficient strength), which is then “pumped” upstream by the asymmetrical tidal action into the Lower North Esk, Home Reach and Yacht Basin areas.

European settlement has exacerbated this natural process by reducing the tidal prism with built infrastructure around Home Point, and because of poor land management practices in the catchments.

A history of dredging and raking from the 1880s to today have not made any permanent impression on the volume of silt stored in the Lower North Esk/Home Reach/Yacht Basin area as all the Launceston residents will attest. Whether the South Esk has flowed through the Cataract Gorge or Tailrace has made very little difference to the end result as the normal volume of water flowing down the South Esk is swamped by the much stronger tidal prism, except in times of floods when the flood waters will top the Trevallyn Dam anyway.

It was on this historical premise and based on a study of all the reports prepared for the Launceston Council from Foster in 1986 to BMT WBM in 2010, that the not-for-profit, community funded, Tamar Lake Inc., was formed to investigate the feasibility of a strategic transformational solution to the continued silt accumulation that involved the removal of the flocculation zone and asymmetrical tidal action from the Upper Reaches with the formation of a large freshwater lake with a barrage situated at the south end of Long Reach, near Bell Bay.

After five years of uncounted hours of technical evaluations and $500,000 of member funded and pro-bono consultancies performed by world-class specialists, the final report, which is expected to be released in the next two weeks, will show that Tamar Lake provides not only a permanent solution to the silt accumulation problem in the upper reaches, but also provides the basis for an economic transformation of the whole Tamar Valley.

The pre-requisite, however, to this economic transformation, is the implementation of the Launceston Sewerage Improvement Plan by TasWater with tertiary treatment of the effluent discharge into the Tamar at Ti-Tree Bend to EPA agreed standards for discharge into a freshwater lake environment.

Does Tasmania, and Launceston in particular, have the leadership and strength of character necessary to implement both these major projects and thereby meet the expectations for water quality and navigation around Launceston that is being demanded by the community?

Robin Frith is a retired engineer.