Within the World Heritage Thirlmere Lakes National Park are five unpolluted fresh water lakes approximately 15 million years old.
The lakes are recognised as being unique becausethe size and unusual shape of the lakes’ catchment area has allowed the uninterrupted development of deep peaty deposits for at least 100000 years, and the stability of the landscape has enabled many aquatic organisms to evolve in isolation. Consequently, this area is an outdoor laboratory of great scientific importance.
Since the early 2000’s declining water levels were observed by locals, to the point that in December 2009, Lake Nerrigorang was only dry cracked peat. By late 2011, Lakes Gandandarra and Werri Berri were also dry. While drought conditions had prevailed through much of the decade, attention also turned to nearby longwall mining activities as a potential cause for the declining water levels.
Despite their significance, no measurements of flows, water levels, or even ground- levels, had been historically undertaken at the Thirlmere Lakes.
An ongoing independent study has sought to piece together the evidence of historical water levels in the five lakes, and to assess the case for impacts from mining, or otherwise. Various lines of evidence were considered, including: historic bushwalker and forestry records; anecdotal evidence; terrestrial photographs; ecological indicators; ground-survey and drilling data; ongoing water level monitoring and mining records and water usage. Industry-standard hydrological and hydrogeological modelling tools were used to replicate the historical water-balance and to assess possible impacts of the nearby longwall mining.