Data from: Seasonal Variation in Methane Ebullition in a Temperate Hydropower Reservoir Related to Drawdown

Estimates of methane (CH4) emissions from freshwaters, including hydropower reservoirs, are highly uncertain, often based on annualization or upscaling from snapshot sampling events during the summer when water levels are high. Some uncertainty in these estimates exists because CH4 emissions, particularly via the ebullition (bubbling) pathway, are highly variable, and are sensitive to hydrostatic pressure and oxidation potential that varies with water depth. However, reservoir-wide estimates of CH4 ebullition often do not account for water depth variability or the size of the “ebullition zone”, potentially contributing to high uncertainty in CH4 emissions. In a case study of Douglas Reservoir, Tennessee, USA, we conducted a monthly sampling campaign March 2023 to March 2024 to capture annual temporal variation in CH4 ebullitive fluxes and the size of the ebullition zone due to seasonal fluctuations in reservoir water levels. This dataset includes the approximately monthly CH4 ebullition rates measured at 20 sites across Douglas Reservoir, along with the corresponding water depth at each site which fluctuated throughout the year due to seasonal drawdown. Additional information and data on drawdown at Douglas Reservoir can be found here: https://www.tva.com/environment/lake-levels/Douglas/Operating-Guide.包括水力发电水库在内的淡水生态系统甲烷（CH4）排放估算结果存在极大不确定性，此类估算通常基于夏季高水位时段的瞬时采样数据进行年度化处理或尺度上推。此类估算存在不确定性的原因在于，甲烷排放——尤其是通过冒泡（ebullition）途径的排放——具有极强的变异性，且对随水深变化的静水压力和氧化还原电位极为敏感。然而，针对水库全域的甲烷冒泡排放估算通常未考虑水深变化以及“冒泡区”的范围，这可能进一步加剧甲烷排放估算的不确定性。本研究以美国田纳西州道格拉斯水库（Douglas Reservoir）为案例，于2023年3月至2024年3月开展月度采样工作，以捕捉因水库水位季节性波动导致的甲烷冒泡通量及冒泡区范围的年度时间变化特征。本数据集涵盖道格拉斯水库全域20个采样点的近似月度甲烷冒泡速率测定结果，以及各采样点因季节性水位消落而全年波动的对应水深数据。有关道格拉斯水库水位消落的更多信息与数据，可通过以下链接获取：https://www.tva.com/environment/lake-levels/Douglas/Operating-Guide。