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，要求各国将洪涝土地的温室气体(GHG)排放纳入国家清单报告。拟议的估算方法依赖于每个气候区排放量的简单平均值，这不适合加拿大等具有不同景观的大国。这项提议旨在获得必要的数据，以便根据加拿大的情况评估和校准现有模型，但也要开发新的模型，以模拟甲烷(CH4)和二氧化碳(CO2)的内部动态，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联合实施强有力的采样计划。由此产生的数据将产生五个主要可交付成果。(1)它将提供来自加拿大不同水库系统的第一组标准化经验数据，这些数据将被用于验证和校准现有的统计模型，以及一种基于过程的物理-生物地球化学方法，以模拟各种环境下的CH4和CO2动态。(2)我们将更好地约束水生温室气体通量途径中最易变化和最难测量的两个组分，即大坝下游的CH4鼓泡和温室气体脱气，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对研究较少的水库类型的适用性，这些水库类型也在北美占主导地位，如防洪和低流量增流。(4)我们将评估如何调整水库调度(水位控制)，以减少水库的温室气体足迹。(5)最后，我们将向我们的政府合作伙伴(ECCC)提供使用加拿大校准的G-RES和基于过程的模型对全国水库足迹总体的估计。总体而言，该方法将为加拿大提供一种更新和动态的方法，以估计该国目前(和未来)被洪水淹没的土地的温室气体足迹，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.