Impact assessment of reservoir operation in the context of climate change adaptation in the Chao Phraya River basin

Abstract

Climate change adaptation has become the current focus of research due to the remarkable potential of climate change to alter the spatial and temporal distribution of global water availability. Although reservoir operation is a potential adaptation option, earlier studies explicitly demonstrated only its historical quantitative effects. Therefore, this article evaluated the possibility of reservoir operation from an adaptation viewpoint for regulating the future flow using the H08 global hydrological model with the Chao Phraya River basin as a case study. This basin is the largest river system in Thailand and has often been affected by extreme weather challenges in the past. Future climate scenarios were constructed from the bias‐corrected outputs of three general circulation models from 2080 to 2099 under RCP4.5 and RCP8.5. The important conclusions that can be drawn from this study are as follows: (i) the operation of existing and hypothetical (i.e., construction under planning) reservoirs cannot reduce the future high flows below the channel carrying capacity, although it can increase low flows in the basin. This indicates that changes in the magnitude of future high flow due to climate change are likely to be larger than those achieved by reservoir operation and there is a need for other adaptation options. (ii) A combination of reservoir operation and afforestation was considered as an adaptation strategy, but the magnitude of the discharge reduction in the wet season was still smaller than the increase caused by warming. This further signifies the necessity of combining other structural, as well as non‐structural, measures. Overall, this adaptation approach for assessing the effect of reservoir operation in reducing the climate change impacts using H08 model can be applied not only in the study area but also in other places where climate change signals are robust.

Inclusion of flood diversion canal operation in the H08 hydrological model with a case study from the Chao Phraya River Basin – Part 1: Model development and validation

“…We previously adapted the H08 model to the calculation domain of 13-20°N and 97-102°E at a spatial resolution of 5 arcmins for application in the CPRB (Padiyedath Gopalan et al, 2021). In that model setup, only three modules (land surface hydrology, river routing, and reservoir operation) of the H08 model were enabled.…”

“…Therefore, the incorporation of diversion canals in combination with reservoir operation could mitigate historic floods. However, climate change will aggravate the risk of flooding in the basin (Padiyedath Gopalan et al, 2021). In light of future climate change, new approaches combining structural and non-structural measures must be adopted in the CPRB.…”

“…The CPRB has been subject to severe flooding in the past, including in recent years (Komori et al, 2012;Kotsuki et al, 2014;Kure and Tebakari, 2012;Watanabe et al, 2014). Recent studies have evaluated the applicabilities of various adaptation strategies, including afforestation (Takata and Hanasaki, 2020) and reservoir operation (Padiyedath Gopalan et al, 2021), for reducing flood risk in the CPRB; they concluded that further adaptation measures are needed to address future floods. Although the CPRB has several natural and man-made diversion canals, their adaptation potential remains largely unknown, because these diversion systems have not been integrated into hydrological models.…”

“…during the wet and dry seasons, with reference to the observed fraction of water diverted. Although the wet season ends in October (section 3.1), May-December was regarded as the wet season in this study based on observed reservoir release(Padiyedath Gopalan et al, 2021) and canal diversion operations. Similarly, the dry season was redefined as January-April for simplicity of simulation.https://doi.org/10.5194/hess-2021-532 Preprint.…”

Reducing Climate Change Induced Flood at the Cost of Hydropower in the Lancang‐Mekong River Basin

“…increase the risk of floods, hydropower reservoir operation, as a potential adaptation option, could help reduce the risks at the cost of the hydropower production (Ngo et al, 2018;Padiyedath Gopalan et al, 2021;Shrestha et al, 2013;Thomas et al, 2021). Future hydropower generation in LMRB has been assessed under climate change, but considering only three upstream reservoirs (Zhong et al, 2019).…”