Assessing the impacts of reservoir operation to floodplain inundation by combining hydrological, reservoir management, and hydrodynamic models

Abstract

A catastrophic flood event which caused massive economic losses occurred in Thailand, in 2011.Several studies have already been conducted to analyze the Thai floods, but none of them have assessed the impacts of reservoir operation on flood inundation. This study addresses this gap by combining physically based hydrological models to explicitly simulate the impacts of reservoir operation on flooding in the Chao Phraya River Basin, Thailand. H08, an integrated water resources model with a reservoir operation module, was combined with CaMa-Flood, a river routing model with representation of flood dynamics. The combined H08-CaMa model was applied to simulate and assess the historical and alternative reservoir operation rules in the two largest reservoirs in the basin. The combined H08-CaMa model effectively simulated the 2011 flood: regulated flows at a major gauging station have high daily NSE-coefficient of 92% as compared with observed discharge; spatiotemporal extent of simulated flood inundation match well with those of satellite observations. Simulation results show that through the operation of reservoirs in 2011, flood volume was reduced by 8.6 billion m 3 and both depth and area of flooding were reduced by 40% on the average. Nonetheless, simple modifications in reservoir operation proved to further reduce the flood volume by 2.4 million m 3 and the depth and area of flooding by 20% on the average. By modeling reservoir operation with a hydrodynamic model, a more realistic simulation of the 2011 Thai flood was made possible, and the potential of reducing flood inundation through improved reservoir management was quantified.

A global hydrological simulation to specify the sources of water used by humans

“…The model has participated in major international model inter-comparison projects, such as EU Water and Global Change (EU-WATCH; Haddeland et al, 2011) and InterSectoral Impact Model Intercomparison Project (ISIMIP; Schewe et al, 2014;Haddeland et al, 2014), to identify its strengths and weaknesses among the other influential models that are currently available. Recently, H08 has been applied in regional domains, with calibrated hydrological parameters Mateo et al, 2014;Masood et al, 2015).…”

Human–water interface in hydrological modelling: current status and future directions

“…1, middle right panel), emphasizing that these processes should be incorporated into state-of-the-art hydrological models. Modelling flood events without human water management would also yield a very different picture, particularly in developed countries where regional water storage and dikes are prevalent for flood mitigation (Lauri et al, 2012;Mateo et al, 2014). Without considering these regional measures, flood events could be largely overestimated in hydrological model simulations.…”

“…Some models allow users to set the spatial domain and resolution freely. Mateo et al (2014) applied the H08 model (Hanasaki et al, 2008a, b) to the Chao Phraya River in Thailand at a spatial resolution of 5 by 5 . Unlike the above-mentioned global studies, they tuned several important hydrological parameters at major river gauging stations by collecting historical meteorological and hydrological data.…”

The 2011 Great Flood in Thailand: Climate Diagnostics and Implications from Climate Change

“…Apart from climatic causes, the extreme flood in 2011 also could have resulted from other factors that involve human activities and civil engineering, such as types of land cover, land-use change (Sriwongsitanon and Taesombat 2011;Jothityangkoon et al 2013), interactions between a river channel and its natural and/or constructed flood plain (Trigg et al 2013), and impacts of reservoir operation (Mateo et al 2014). Water Rakwatin et al 2013;Haraguchi and Lall 2014;Mateo et al 2014).…”

“…Water Rakwatin et al 2013;Haraguchi and Lall 2014;Mateo et al 2014). As Komori et al (2012) pointed out, had the water been drained from these reservoirs earlier in the monsoon season (instead of storing it as is common practice), 1 3 10 9 m 3 of floodwater could have been stored in the reservoirs during the monsoon season.…”