Integrated flood countermeasures in the upper and middle Chao Phraya River Basin

Hanasaki

et al. 2020

Hydrological Processes

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.

Section: Effect Of Hypothetical and Existing Reservoirs To Tackle Tsupporting

confidence: 80%

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

Hanasaki

et al. 2020

Hydrological Processes

“…In most Southeast Asian countries, rainfed cropland comprises low-lying paddy fields that are natural floodplains and cannot be cultivated during the rainy season because of flooding (Jamrussri et al, 2018). Thus, for the sake of brevity, the areal fraction of rainfed croplands (Siebert et al, 2010), presumably located near the canal route, was regarded as the areal fraction of retention areas for both canal schemes because our region of interest is in a Southeast Asian country.…”

Section: Input Data Sources and Assumptions For Canal Operation In Th...mentioning

confidence: 99%

“…This finding elucidates the need for (i) water diversion systems to divert floodwater from the upper to lower basin, (ii) more retention areas to store floodwater, and (iii) other structural and non-structural measures. Jamrussri et al (2018) also suggested that new retention areas adjacent to the Yom and the Nan rivers are necessary to overcome severe flooding in the upper basin. The effect of water diversion on discharge is more pronounced in the lower CPRB.…”

Section: Impact Of Canal Systems On Flood Controlmentioning

confidence: 99%

Inclusion of flood diversion canal operation in the H08 hydrological model with a case study from the Chao Phraya River basin: model development and validation

Hydrol. Earth Syst. Sci.

Sukhapunnaphan

et al. 2022

Abstract. Water diversion systems play crucial roles in assuaging flood risk by diverting and redistributing water within and among basins. For flood and drought assessments, including investigations of the effects of diversion systems on river discharge worldwide, the explicit inclusion of these systems into global hydrological models (GHMs) is essential. However, such representation remains in the pioneering stage because of complex canal operations and insufficient data. Therefore, we developed a regionalized canal operation scheme and implemented it in the H08 GHM for flood diversion in the Chao Phraya River basin (CPRB), Thailand, which is a complex river network with several natural and artificial diversion canals and has been subject to severe flooding in the past, including recent years. Region-specific validation results revealed that the enhanced H08 model with the regionalized diversion scheme could effectively simulate the observed flood diversion pattern in the CPRB. Diverted water comprises approximately 49 % of the annual average river discharge in the CPRB. The simulations further confirmed that the presented canal scheme had the potential to reduce flood risk in the basin by significantly reducing the number of flooding days. A generalized canal scheme with simple input data settings was also constructed for future global applications, providing insights into the maximum level of discharge reduction achievable with diversion of nearly 57 % of the annual average river discharge of the CPRB. Overall, the enhanced H08 model with canal schemes can be adapted and applied to different contexts and regions, accounting for the characteristics of each river network by maintaining the basic principles unaltered.

“…Irrigation water is applied to the irrigation sub-cells to maintain appropriate soil moisture during the cropping period, while no irrigation is supplied to rainfed and non-cropland sub-cells (Hanasaki et al, 2018). In most Southeast Asian countries, rainfed cropland comprises low-lying paddy fields that are natural floodplains and cannot be cultivated during the rainy season because of flooding (Jamrussri et al, 2018). Thus, for the sake of brevity, the areal fraction of rainfed croplands (Siebert et al, 2010) presumedly located near the canal route was regarded as the areal fraction of retention areas for both canal schemes because our region of interest is in a Southeast Asian country.…”

Section: Input Data Sources and Assumptions For Canal Operation In The Cprbmentioning

confidence: 99%

“…Jamrussri et al (2018) also suggested that new retention areas adjacent to the Yom and the Nan Rivers are necessary to overcome severe flooding in the upper basin. The effect of water diversion on discharge is more pronounced in the lower CPRB.Furthermore, the effect of canal operation on flood control was examined by calculating the number of flooding days (days during which daily discharge exceeded the channel carrying capacity) at various locations, as shown in Fig.8.…”

mentioning

confidence: 99%

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

Sukhapunnaphan

et al. 2021

Preprint

Abstract. Water diversion systems play crucial roles in assuaging flood risk by diverting and redistributing water within and among basins. For flood and drought assessments, including investigations of the effects of diversion systems on river discharge worldwide, the explicit inclusion of these systems into global hydrological models (GHMs) is essential. However, such representation remains in the pioneering stage because of complex canal operations and insufficient data. Therefore, we developed a regionalized canal operation scheme and implemented it in the H08 GHM for flood diversion in the Chao Phraya River Basin (CPRB), Thailand, which is a complex river network with several natural and man-made diversion canals and has been subject to severe flooding in the past, including recent years. Region-specific validation results revealed that the enhanced H08 model with the regionalized diversion scheme could effectively simulate the observed flood diversion pattern in the CPRB. Diverted water comprises approximately 49 % of the annual average river discharge in the CPRB. The simulations further confirmed that the presented canal scheme had the potential to reduce flood risk in the basin by significantly reducing the number of flooding days. A generalized canal scheme with simple input data settings was also constructed for future global applications, providing insights into the maximum level of discharge reduction achievable with diversion of nearly 57 % of the annual average river discharge of the CPRB. Overall, the enhanced H08 model with canal schemes can be adapted and applied to different contexts and regions, accounting for the characteristics of each river network by maintaining the basic principles unaltered.