Development of a reservoir model to improve evapotranspiration estimates in a regional land atmospheric model

The community land model (CLM) was designed for coupling with atmospheric model to simulate the water, energy, and carbon fluxes between the land surface and atmosphere. These fluxes are regulated in various degrees by its hydrologic processes, which have not been vigorously evaluated for applications at watershed or regional scales. In the framework of an integrated regional earth system model being developed, accurate hydrologic information in all of its components including socio-economy, atmosphere, land, and energy infrastructure is needed to represent the interactions between human and earth system processes. Incorporating CLM in this framework requires model evaluation and improvement so that CLM could be used to represent hydrology, soil, managed and unmanaged ecosystems, and biogeochemical processes across scales in a coherent modeling framework. As part of this effort, an irrigation-runoff routing-reservoir model is developed as a relatively simple and generic way to represent water management in CLM, which only deals with natural land surface and hydrologic processes. The objective is to improve evapotranspiration estimates in time and space resulting from human influence, i.e., from irrigation and large reservoir storage. Once fully coupled, it will also allow i) assessing the feedback of increased evapotranspiration in an atmospheric model, ii) investigations of water use and its influence on other human and earth system components. The concept of the preliminary reservoir model is presented over the Columbia River Basin. Challenges due to the differences in time and spatial scales between the physical processes versus reservoir operations and targets (irrigation, flood control, hydropower generation, navigation, environmental flow) are discussed.