Sustainable management of Central Victorian mineral waters

Central Victoria contains more than 100 carbonated mineral water springs, many were discovered when uncovered by alluvial gold mining activities of the 1850's. The mineral springs are located at distances of 2 to 45 km from the crest of the Great Dividing Range, and are situated at elevations from 700 down to 200 m above sea level. The discharge from individual springs is small, and usually falls in the range 0.01 0.4 L/s (0.3-13 ML/annum). The mineral spring waters are cold ranging from around 10o C at the higher elevations to 17o C at the springs occurring at lower elevations.<br><br>The carbonated mineral waters are a facies of the more widely distributed high bicarbonate alkalinity groundwater in the deep circulation systems of Central Victoria. The carbonated mineral waters are mildly acidic (pH 5.7 - 6.3), oxidic (Eh +50 to +100 mv), have low chloride (median 60 mg/L), high bicarbonate (median 1500 mg/L) and low sulphate (median 18 mg/L) concentrations. The water becomes slightly effervescent on discharge from the springs, and may be vigorously gassy when escaping from bores in the ascension zone. The characteristics of the mineral water chemistry may be explained by clay reactions - proton exchange, carbonate dissolution and base exchange. In the ascension zone heterogeneous thermodynamics, including the dissociation characteristics of a diprotic acid, acidity regulation by non carbonate equilibria, in particular by iron chemistry results in effervescence as pressure, degassing, acidity change and electro neutrality determine the water chemistry. Local characterisation of the m ineral waters arises from a superimposition of flux and mixing relationships encountered in discharge or ascension zones on regional trends.<br><br>In Central Victoria the bedrock aquifer consists of interbedded lithic and arkosic grits, sandstones and graphitic shales. The most common occurrence is in rocks of Lower Ordovician age, but mineral waters also occur in Cambrian, Upper Silurian and Lower Devonian strata. The rocks have been subjected to variable but low grade regional metamorphism. Sandstone and grit units may retain some primary porosity, and thin intersections of unconsolidated sediment occur in bore holes. Narrow bands of saccharoidal marble and cone-in-cone limestone are present, but carbonates are a minor constituent of the rock mass (0.5% - 2%) and associated diagenetic ankerite. Organic carbon may exceed 5% in the black graphitic shales. Deep weathering profiles are developed on these rocks with elution of carbonates and kaolinisation silicate minerals. The rocks are folded asymmetrically and cut by strongly developed concordant meridional bearing thrust faults. The linear character of the rock mass failure produces anisotropy and heterogeneity. Deep fissure flow systems emanating from the Great Dividing Range follow litho structural corridors for distances of more than 40 km and groundwater has been observed in the bedrock mines of Central Victoria at depths of more than 1.6 km.<br><br>The sustainable management of the mineral water resource involves the maintenance of yield, water quality and public equity. Sustaining Public Equity was initiated in 1865 by the formal establishment of mineral spring reserves. Reserves were proclaimed to preserve the springs from 'the ravages of mining, and for public recreation and amusement'. At Hepburn the first Pavilion was erected in 1869; a bottling plant in 1880 and a bath house was built in 1890. The region is the centre of balneology and hydrotherapy in Victoria and provides a 150 year history of development, conflict and sustainable resource management resolution. The spring reserves and surrounding buffer areas in the planning schemes offer protection for the discharge zones, but there is increasing tendency to commercialise and encroach on the reserves and allocate the mineral water for commercial or semi commercial development. Past evidence illustrates that management of the water quality, its salinity and gas content, is equally difficu lt as the maintenance of the flow of the springs and the continuation of public equity. Long term sustainable management is an evolving process that recognises past failures and crises. It shares the failure profile exhibited in many examples of overseas development of mineral and thermal waters. Legal Principles and endeavours outside the jurisdiction of the water and environment protection sectors are pre-eminent in the decision making processes. Nevertheless, the existing regulatory processes do have the potential to protect the resource.