Freshwater reservoirs are hotspots for methane (CH4) and carbon dioxide (CO2) fluxes released into the atmosphere; however, there is little knowledge about CO2 flux rates from reservoirs in Mediterranean climate regions. Studies show that reservoirs can either emit or absorb CO2, depending on the season and time of day. The goal of this study was to analyze CO2 and gain knowledge of the temporal variability of CO2 fluxes at Uvas Reservoir, Santa Clara County, California, in a Mediterranean climate zone. Results showed a strong diel variability of CO2, with negative flux rates (CO2 sinks) generally occurring during the nighttime. For example, in June 2021 at Uvas Reservoir, CO2 emissions decreased from -0.27 mg m-2 h-1 to -0.48 mg m-2 h-1 at night. These fluxes were also variable seasonally, where positive values (CO2 sources) in CO2 flux rates occurred during fall turnover, with a peak flux rate calculated at +1.57 mg m-2 h-1 in the daytime. This example from the fall season occurred after the reservoir had used up all the nutrients and when algae were decomposing. Lastly, the CO2 surface gas flux results from Uvas Reservoir were compared to other freshwater reservoirs within the same climatic region, different climatic regions, and other land classification types. This comparative analysis showed that Uvas Reservoir had 20% and 6.2% higher CO2 flux rates compared to a tropical climate and a temperate climate in a dry year, respectively.
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机译：淡水储层是释放到大气中的甲烷 （CH4） 和二氧化碳 （CO2） 通量的热点;然而，人们对地中海气候地区储层的 CO2 通量率知之甚少。研究表明，水库可以排放或吸收 CO2，具体取决于季节和一天中的时间。本研究的目的是分析 CO2 并了解位于地中海气候区的加利福尼亚州圣克拉拉县 Uvas 水库的 CO2 通量的时间变化。结果表明 CO2 具有很强的 diel 可变性，负通量率（CO2 汇）通常发生在夜间。例如，2021 年 6 月，乌瓦斯水库的 CO2 排放量从夜间的 -0.27 mg m-2 h-1 下降到 -0.48 mg m-2 h-1。这些通量也随季节变化，其中 CO2 通量率的正值（CO2 来源）出现在秋季周转期间，白天计算的峰值通量率为 +1.57 mg m-2 h-1。这个来自秋季的例子发生在水库用完所有营养物质和藻类分解之后。最后，将 Uvas 油藏的 CO2 地表气通量结果与同一气候区、不同气候区和其他陆地分类类型的其他淡水储层进行了比较。该比较分析表明，与热带气候和温带气候相比，乌瓦斯水库在干旱年份的 CO2 通量率分别高出 20% 和 6.2%。
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