Constraining the greenhouse gas footprint of Canada's flooded lands

2019年，政府间气候变化专门委员会（IPCC）通过了一份新的方法报告，要求各国将洪水淹没土地的温室气体排放纳入其国家清单报告。拟议的估算方法依赖于每个气候带的排放量的简单平均值，不适合像加拿大这样景观多样的大国。该提案旨在获取必要的数据，以评估和校准加拿大环境下的现有模型，同时也开发新的模型来模拟甲烷（CH4）和二氧化碳（CO2）的内部动力学，并估计它们通过多种排放途径释放到大气中。特别是，我们将与多个合作伙伴（水电公司、ECCC、保护当局）合作，在不同的水库中建立并共同实施一个强有力的抽样计划。由此产生的数据将产生五个主要成果。(1)它将提供来自加拿大不同储层系统的第一套标准化的经验数据，这些数据将反过来用于验证和校准现有的统计模型，以及基于过程的物理生物地球化学方法来模拟各种环境下CH4和CO2的动态。(2)对CH4冒泡和大坝下游温室气体脱气这两个变化最大、最难测量的水体温室气体通量途径进行约束，并将其与基于过程的方法相结合。(3)我们将评估我们的新方法在北美研究较少的水库类型、洪水控制和低流量增加方面的适用性。(4)评价如何通过水库运行（水位控制）来减少水库的温室气体足迹。(5)最后，我们将使用加拿大校准的G-res和基于过程的模型，向我们的政府合作伙伴（ECCC）提供国家水库足迹的总体估计。总的来说，该方法将为加拿大提供一种最新的动态方法来估计该国洪水土地当前（和未来）的温室气体足迹，并提供可在国外动员的一般知识和工具。

In 2019, the Intergovernmental Panel on Climate Change (IPCC) adopted a new Methodology Report that require countries to include greenhouse gas (GHG) emissions from flooded lands in their National Inventories Report. Proposed estimation approaches rely on simple averages of emissions rates per climate zone, inappropriate for large countries with diverse landscapes such as Canada. This proposal aims at acquiring the data necessary to assess and calibrate existing models to the Canadian context but also to develop new models to simulate the internal dynamics of methane (CH4) and carbon dioxide (CO2) and estimate their release to the atmosphere through the multiple emissions pathways. In particular, we will engage with multiple partners (hydropower companies, ECCC, conservation authorities) to establish and jointly conduct a robust sampling program in a diverse set of reservoirs. The resulting data will yield five main deliverables. (1) It will provide the first standardized set of empirical data from diverse Canadian reservoir systems that will in turn be used to validate and calibrate existing statistical models as well as a process-based physical-biogeochemical approach to model CH4 and CO2 dynamics across various environmental settings. (2) We will better constrain the two most variable and difficult to measure components of aquatic GHG flux pathways, namely CH4 bubbling and GHG degassing downstream of dams, and integrate those with the process-based approach. (3) We will evaluate the applicability of our new approach to the lesser studied reservoir types that also dominate North America, flood control and low flow augmentation. (4) We will evaluate how reservoir operations (water level control) can be adapted to reduce the GHG footprint of reservoirs. (5) Lastly, we will provide our governmental partner (ECCC) with estimates of the ensemble of the nation's reservoir footprint using both the Canadian calibrated G-res and process-based models. Overall, the approach will provide Canada with an updated and dynamic methodology to estimate the current (and future) GHG footprint of the nation's flooded land as well as provide general knowledge and tools that could be mobilized abroad.