Abstract
Lake Inawashiro is an important drinking water source for Koriyama City, Fukushima Prefecture, where geosmin, an earthy odor compound, is occasionally detected during summer. This study examined the relationship between surface water temperature and geosmin concentration using routine monitoring data around the Hamaji intake tower. Geosmin concentrations were analyzed as detection events at ≥1 ng L⁻¹ and as caution-level events at ≥3 ng L⁻¹. A generalized additive model was used to estimate exceedance probability as a function of surface water temperature. Receiver Operating Characteristic curves and the Area Under the Curve were also calculated to evaluate the discriminatory ability of surface water temperature. The AUC for caution-level events was 0.842. These results suggest that surface water temperature may serve as an empirical indicator of an increased risk of geosmin concentrations reaching the caution level.
