A simple approach to estimate lake surface water temperatures in Polish lowland lakes

Study region: Lowland lakes located at Poland. Study focus: There are thousands of lowland lakes in Poland, however, many of them don’t have observed data of water temperatures. How can we simply estimate lake surface water temperature (LSWT) is challenging, and a few studies tried to deal with this issue. In this study, we proposed a simple method using the air2water model for regional estimation of LSWT for Polish lowland lakes: Firstly, a literature review was conducted to collect parameter values of the air2water model applications in different lakes with diverse lake morphologies (e.g., mean depth). Secondly, correlations of model parameters with mean lake depth were analyzed. Finally, model parameters of the Polish lowland lakes (25 lakes with three lakes for testing) were derived using the corresponding mean lake depth and model performance was evaluated afterwards. New hydrological insights for the region: The results showed that the proposed method performs generally well for the 25 Polish lowland lakes, better than the previous method. Reasonable results were obtained for three Polish lakes that were not used for regression analysis, what encourages application of the proposed approach on unmonitored lakes. The results indicated that the method proposed in this study can be used to estimate LSWT of Polish lowland lakes as daily data of air temperatures are readily available in most of the meteorological stations.