Future climate warming may increase water temperature, stratification, and the occurrence of cyanobacteria blooms in drinking water reservoirs. Herein, past relationships between air temperature, water temperature, thermal stratification, and cyanobacteria prevalence are quantified in six Connecticut, U.S.A., reservoirs. Lake‐specific empirical models were developed and used to project historical (1971–2000) and future (mid‐century, 2041–2070) water temperature and thermal stratification in the study lakes. Projections are driven with downscaled air temperature projections from three general circulation models (i.e., HadGEM2‐CC365, CCSM4, and GFDL‐ESM 2M) under Representative Concentration Pathway 8.5. Results suggest that reservoirs in Connecticut are warming relatively quickly over time and that surface, average, and bottom water temperatures may continue to increase by 0.44°C, 0.30°C, and 0.16°C per decade, respectively. Future projections of thermal stratification indicate that significant increases may occur in July–September and that stratification is likely to begin 2–4 weeks earlier and last 2–4 weeks longer by mid‐century. High‐risk cyanobacteria blooms, defined as those exceeding 70,000 cells ml⁻¹, historically occurred in three of the study reservoirs and are correlated with the occurrence of high surface water temperatures, cool bottom water temperatures, and high total Relative Thermal Resistance to Mixing (RTRM). Days per year with extreme high water temperatures and total RTRM are projected to increase significantly in the future. This shift may favor increased dominance of certain cyanobacteria species that tend to grow best in these extreme conditions, especially in reservoirs where cyanobacteria blooms are already a concern.

中文翻译：

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康涅狄格州水库水温和热分层的未来预测及其对蓝细菌的潜在影响

未来的气候变暖可能会增加水温，分层和饮用水水库中蓝细菌绽放的发生。在此，在美国康涅狄格州的六个水库中，对气温，水温，热分层和蓝细菌流行率之间的过去关系进行了定量。开发了针对湖泊的经验模型，并用于预测研究湖泊的历史（1971–2000）和未来（本世纪中叶，2041-2070）的水温和热分层。在“代表浓度路径8.5”下，使用来自三种通用循环模型（即HadGEM2-CC365，CCSM4和GFDL-ESM 2M）的降尺度的气温预测来驱动投影。结果表明，康涅狄格州的水库随着时间的推移相对较快地变暖，平均而言，每十年，底水温度可能会分别继续升高0.44°C，0.30°C和0.16°C。热分层的未来预测表明，七月至九月可能会出现显着增加，并且分层可能会在2-4周之前开始，并在本世纪中叶之前持续2-4周。高风险蓝藻繁殖，定义为超过70,000个细胞ml^-1，历史上发生在三个研究水库中，并与地表水温度高，底部水温低和混合总相对热阻（RTRM）高有关。预计未来每天水温极高和总RTRM的天数将大大增加。这种转变可能有利于增加某些在这些极端条件下往往生长最佳的蓝细菌物种的优势地位，特别是在蓝藻水华已经引起人们关注的水库中。