A case study investigating the occurrence of geosmin and 2-methylisoborneol (MIB) in the surface waters of the Hinze Dam, Gold Coast, Australia.

The Hinze Dam is located in the Gold Coast hinterland and is the primary source of water supply for the Gold Coast region. Sporadic and unpredictable taste and odour events caused by geosmin and 2-methylisoborneol (MIB) are an ongoing problem in the Hinze Dam. To investigate potential ecological and physiological triggers of these events, a 12-month surface-sampling regime was undertaken. Concentrations of geosmin, MIB, nitrogen and phosphorus were measured. Algal and cyanobacterial counts were performed. Water temperature, rainfall and dam capacity were also recorded. The occurrence of geosmin was found to correlate significantly with Anabaena numbers, water temperature and dam capacity. The occurrence of MIB correlated with increasing ammonia. No significant correlations were observed with the other nutrients or physical parameters measured. Overall, this study demonstrated that high concentrations of geosmin detected in dam surface waters was strongly correlated with an increase in numbers of Anabaena spp. These events were most likely triggered by significant rainfall causing a pulse in nutrients into the dam, in conjunction with warmer water temperatures.