Reservoirs in arid regions often provide critical water storage but little is known about their greenhouse gas (GHG) footprint. While there is growing appreciation of the role reservoirs play as GHG sources, there is a lack of understanding of GHG emission dynamics from reservoirs in arid regions and implications for environmental policy. Here we present initial GHG emission measurements from Lake Powell, a large water storage reservoir in the desert southwest United States. We report CO₂-eq emissions from the shallow (< 15 m) littoral regions of the reservoir that are higher than the global average areal emissions from reservoirs (9.4 vs. 5.8 g CO₂-eq m⁻² d⁻¹) whereas fluxes from the main reservoir were two orders of magnitude lower (0.09 g CO₂-eq m⁻² d⁻¹). We then compared our measurements to modeled CO₂ + CH₄ emissions from the reservoir using four global scale models. Factoring these emissions into hydropower production at Lake Powell yielded low GHG emissions per MWh⁻¹ as compared to fossil-fuel based energy sources. With the exception of one model, the estimated hydropower emissions for Lake Powell ranged from 10−32 kg CO₂-eq MWh⁻¹, compared to ∼400−1000 kg CO₂-eq MWh⁻¹ for natural gas, oil, and coal. We also estimate that reduced littoral habitat under low water levels leads to ∼50% reduction in the CO₂ equivalent emissions per MWh. The sensitivity of GHG emissions to reservoir water levels suggests that the interaction will be an important policy consideration in the design and operation of arid region systems.

干旱地区的水库通常提供重要的储水作用，但人们对其温室气体 (GHG) 足迹知之甚少。尽管人们越来越认识到水库作为温室气体源的作用，但人们对干旱地区水库的温室气体排放动态及其对环境政策的影响缺乏了解。在这里，我们展示了鲍威尔湖（美国西南部沙漠中的一个大型水库）的初始温室气体排放测量结果。我们报告的水库浅海 (< 15 m) 沿岸区域的 CO ₂ -eq 排放量高于水库的全球平均面积排放量（9.4 与 5.8 g CO ₂ -eq m ^-2 d ^-1 ），而来自主水库的通量低两个数量级（0.09 g CO ₂ -eq m ^-2 d ^-1 ）。然后，我们使用四个全球规模模型将测量结果与水库模拟的 CO ₂ + CH ₄排放量进行了比较。将这些排放纳入鲍威尔湖水力发电中，与基于化石燃料的能源相比，每兆瓦时^{-1 的}温室气体排放量较低。除一个模型外，鲍威尔湖的水力发电排放量估计范围为 10−32 kg CO ₂ -eq MWh ^-1 ，而天然气、石油和煤炭的排放量为 ∼400−1000 kg CO ₂ -eq MWh ^-1 。我们还估计，低水位下沿海栖息地的减少导致每兆瓦时 CO ₂当量排放量减少约 50%。温室气体排放对水库水位的敏感性表明，这种相互作用将成为干旱地区系统设计和运行的重要政策考虑因素。