Karst drainage relations with catchment land use change, Mole Creek, Tasmania, Australia

Since 2001, the previously perennial Parsons’ Spring of the Mole Creek fluviokarst in northwestern Tasmania, Australia, has become intermittent in discharge. This change follows the establishment of 636 ha of eucalypt plantations since 1995 above the Spring, including where Quaternary slope deposits obscure the geological contact of the limestone with overlying rocks. In this 2008 study, water quality was compared and contrasted between Parsons’ Spring and other sites in the study catchment and a resurgence in a nearby reference catchment over different flow conditions and in response to a rainstorm. Results show that the study spring has a mixed recharge regime and complex discharge controls, including diffuse and conduit hydrological components. Parsons’ Spring is probably the main wet season overflow spring of a distributary system connected to the phreatic aquifer underlying the area. Apparent chemical ‘signatures’ indicating soil disturbance in the study spring’s waters implied the presence of an epikarst reservoir beneath the slope deposits cultivated for plantation establishment. Given their location, extent and growth stage, the plantations are expected to reduce aquifer recharge substantially by 2013–2018 as interception of recharge increases. The consequent reduction of available aquifer yield would result in economic stress for the rural community and compromise of karst ecosystems.