Development of a Reservoir Flood Control Scheme for Global Flood Models. (12th March 2022)

• Record Type: Journal Article
• Authors: Hanazaki, Risa; Yamazaki, Dai; Yoshimura, Kei
• Is Part Of: Journal of advances in modeling earth systems. Volume 14:Number 3(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-12
• Subjects: dam reservoir -- river flooding -- reservoir operation -- flood control -- global model; Geological modeling -- Periodicals; Climatology -- Periodicals; Geochemical modeling -- Periodicals; 551.5011
• DOI: 10.1029/2021MS002944
• Languages: English
• ISSNs: 1942-2466

Abstract

Abstract: Integrating reservoir flood control operations in global flood forecasting systems is important for accurately estimating discharge and other variables. Because existing modeling operational rules and parameters do not reflect the actual variability due to a lack of associated data, globally applicable modeling of flood regulation needs to be studied further. In this study, we developed a flood control operation scheme with refined parameters and algorithms to tackle this problem. We used recently developed objective data sets of reservoir dynamics to more realistically estimate different reservoir parameters, such as flood storage capacity. Furthermore, the algorithm for the operational rule was modified by introducing a new release coefficient such that the peak attenuation depended on the reservoir's ability to regulate floods. The operation scheme for 2, 169 dams was introduced into the CaMa‐Flood global hydrodynamic model. Compared to the simulation without reservoirs, the Nash‐Sutcliffe Efficiency and peak discharge error in the daily river discharge improved at 62.2% and 49.9% of the gauges, respectively, after the integration. Compared to the parameter estimated by a method in previous studies, the newly estimated flood storage capacity parameters reduced the peak discharge error at 47% of the gauges downstream of the reservoirs where the flood storage capacity ratio is small (≤50%). Furthermore, the modification of operational rules had the effect of mitigating people exposed to flooding by ∼10%. This study informs the integration and the refinements of the reservoir operation scheme to improve global flood simulation and forecasting. Plain Language Summary: Global flood forecasting systems based on numerical modeling have been developed for flood mitigation. The effect of reservoir operation on river discharge should be considered in these systems because dams control the amount of river discharge (reservoir outflow) during floods to reduce damages downstream. In this study, we introduced a new reservoir flood control operation scheme with refined parameters and algorithms into a global flood model. Due to a lack of information on dams and reservoirs around the world, we estimated the required parameters of each reservoir by a novel method using data sets recently developed based on satellite observation. In addition, the algorithm for flood control operations was modified to represent the actual dam operations. Our results showed that the indices of daily river discharge accuracy were improved at about half of the discharge gauges worldwide by implementing the reservoir operation scheme compared to the simulation without dams. Furthermore, the newly estimated parameters reduced errors in peak discharge during floods compared to the parameters estimated in the previous studies. Our results suggest that the introduction and the improvements in the reservoir operation scheme contribute to better flood simulation and therefore are important for flood forecasting. Key Points: Reservoir operation scheme for flood control was introduced into the global flood model Operational rules and parameters were identified to represent the actual flood control operation Developed reservoir operation scheme leads to improvement in discharge simulation during floods and significantly impacts flood mitigation