Papers by Saowanit Prabnakorn
Integrated Flood and Drought Mitigation Measures and Strategies
Floods and droughts are climate extremes that account for more than 80% of people affected by nat... more Floods and droughts are climate extremes that account for more than 80% of people affected by natural disasters worldwide. Both catastrophes co-exist in many river basins, for example, the Mun River Basin in Thailand, which is selected as the study area. Approximately 90% of rice cultivation here is rain-fed, and that results in the lowest yields in the country, making many farmers persist in poverty. This study aims to assess floods and droughts and their impacts on agriculture at the basin scale. For flooding, the hydrologic and hydraulic models were developed to produce the first completed flood hazard maps at the Mun River Basin. Droughts in the basin were determined by the proposed drought risk assessment scheme that combines all three key components (hazard, exposure, and vulnerability). Subsequently, the study attempts to tackle both floods and droughts simultaneously and sustainably by using integrated measures and strategies. If the problems caused by flood and drought climate extremes are solved, this will ensure adequate food availability and alleviate poverty in the basin. Furthermore, the study shows that a holistic approach to simultaneously solving both problems is efficient as most water will be utilized to benefit agriculture, the primary sector that feeds a growing population.
Climate variability, trends, and their impacts on rice yields
CRC Press eBooks, Feb 7, 2020
Synthesis and main contributions & prospects of further research
General introduction
CRC Press eBooks, Feb 7, 2020
Flood Risk Assessment as a Part of Integrated Flood and Drought Analysis. Case Study: Southern Thailand
EGUGA, Apr 1, 2015
x actual average yield). However, if the rising trends in minimum and maximum temperatures persis... more x actual average yield). However, if the rising trends in minimum and maximum temperatures persist, there is a high possibility that the yield losses will become more severe in the future. Next, the identification of flood and drought-prone areas is executed. The inundated areas at 10, 25, 50, and 100-year return period are obtained from an integrated hydrologic (SWAT) and hydraulic (HEC-RAS) model. The flooded areas are larger on the left bank than the right and that the flood depths vary from 0-4 m. About 60% of the floodplain inundation is less than 1 m and mostly found at the upstream and central areas of the river. The flat terrains make flooding duration last long, causing damage to crop growth and yields, particularly rice, which occupies a majority of the area and mostly locates on the river banks. Drought-prone areas are detected by using the proposed comprehensive drought risk assessment scheme that incorporates hazard, exposure, and vulnerability. The hazard is estimated from water deficits calculated with respect to rice water requirement. Exposure is based on population and rice field characteristics, while other physical and socioeconomic factors and coping capacity are used in the estimation of vulnerability. The findings demonstrate that drought hazard is most critical in October, which can reduce rice yields significantly. Rice fields in the central part are more exposed to droughts than in other areas. Extensive land is under high and moderate vulnerability. The higher drought risks emerge in October and November and decrease from north to south. After flood and drought problems are identified, a coping capacity of existing and ongoing water resources development projects are evaluated. The total storage capacity of those projects is sufficient to cope with both hazards, but the performance is inefficient and ineffective. Thus, several pieces of advice are provided to improve the performance of in-situ measures. Moreover, other measures are proposed to complement the existing measures and make the storage system more flexibility. The suggested measures are practicable, applicable, economical, and less environmental impacts. They have the potential to sustainably solve both floods and droughts in order to enhance rice production in the basin. This study provides all dimensions associated with floods and droughts, their impacts on rice yields, and mitigation measures to tackle both hazards simultaneously and sustainably. The achievement over the two climate extremes will ensure adequate food availability and alleviate poverty in the basin. Furthermore, the study shows that a holistic approach to simultaneously solving both problems is efficiency as all drops of water are utilized to benefit agriculture, the primary sector that feeds a growing population. 1 General introduction 1.1 Floods and droughts 1.1.1 Flooding 1.1.2 Drought 1.2 Impacts on agriculture 1.3 Research gaps 1.4 Selection of the study area and scope of the study 1.5 Research objectives 1.6 Outline of the thesis References 2 Chapter 1 1.1 Floods and droughts Floods and droughts are the two main meteorological catastrophes. Flooding occurs the most (33%), whereas droughts are less frequent (5%-Table 1-1), but cause more fatal impacts in terms of the number of the death toll. Combined, the hazards account for 80% of the total number of people affected by natural disasters (Table 1-2). Furthermore, they have created enormous environmental, social, and economic impacts, such as degraded wetland areas, diminished natural biodiversity, destroyed agricultural land and industrial facilities, and high economic costs. It is expected that climate change effects (i.e., more intense rainfall, increasing seawater levels, etc.) will exacerbate flood occurrences and impacts in the future (
Optimizing GRACE/GRACE-FO data and a priori hydrological knowledge for improved global terrestial water storage component estimates
Journal of Hydrology, Jul 1, 2021
Abstract The comprehensive information of global terrestrial water storage (TWS) components (soil... more Abstract The comprehensive information of global terrestrial water storage (TWS) components (soil moisture, groundwater, snow, surface water) is essential for effective assessment of water resource availability, climate variation, and disaster mitigation measures. Observational data provided by the Gravity Recovery And Climate Experiment (GRACE) and GRACE Follow-On satellite missions offer global TWS variation (ΔTWS) in terms of an integrated water column. However, GRACE spatial resolution is relatively coarse (i.e., 3°), and the vertically integrated value cannot be separated into ΔTWS components directly. This study demonstrates the feasibility to estimate ΔTWS components at any desired spatial-vertical resolution by effectively maintaining the native resolution of the employed hydrological knowledge. It utilizes a least-squares with constraints (LSC) approach to rigorously incorporate GRACE and GRACE-FO data and a priori hydrological knowledge, with the aim to improve global ΔTWS components’ accuracy and spatial resolution. The 3°×3° GRACE mascon derived ΔTWS data is disaggregated into the 0.5°×0.5° anomalous soil moisture storage (ΔSMS), groundwater storage (ΔGWS), snow water equivalent (ΔSWE), and surface water storage (ΔSWS) based on the covariance information obtained from the Community Atmosphere Biosphere Land Exchange (CABLE) and the PCRaster Global Water Balance (PCR-GLOBWB) models. Evaluation with different ground measurements and satellite products between 2002 and 2019 exhibits significantly improved accuracy in all individual ΔTWS components. This improvement is of particular note in ΔGWS and ΔSWS, where the LSC approach increases the globally averaged correlation values by approximately 0.13 and 0.05, respectively. Reliable prior knowledge leads to a more accurate ΔTWS component estimate, and the use of ensemble-mean knowledge yields the best result.
Flood Risk Assessment as a Part of Integrated Flood and Drought Analysis. Case Study: Southern Thailand
EGUGA, Apr 1, 2015
Synthesis and main contributions prospects of further research
Integrated Flood and Drought Mitigation Measures and Strategies
Flood and drought mitigation measures and strategies
Drought hazard assessment
Optimizing GRACE/GRACE-FO data and a priori hydrological knowledge for improved global terrestial water storage component estimates
Journal of Hydrology
Abstract The comprehensive information of global terrestrial water storage (TWS) components (soil... more Abstract The comprehensive information of global terrestrial water storage (TWS) components (soil moisture, groundwater, snow, surface water) is essential for effective assessment of water resource availability, climate variation, and disaster mitigation measures. Observational data provided by the Gravity Recovery And Climate Experiment (GRACE) and GRACE Follow-On satellite missions offer global TWS variation (ΔTWS) in terms of an integrated water column. However, GRACE spatial resolution is relatively coarse (i.e., 3°), and the vertically integrated value cannot be separated into ΔTWS components directly. This study demonstrates the feasibility to estimate ΔTWS components at any desired spatial-vertical resolution by effectively maintaining the native resolution of the employed hydrological knowledge. It utilizes a least-squares with constraints (LSC) approach to rigorously incorporate GRACE and GRACE-FO data and a priori hydrological knowledge, with the aim to improve global ΔTWS components’ accuracy and spatial resolution. The 3°×3° GRACE mascon derived ΔTWS data is disaggregated into the 0.5°×0.5° anomalous soil moisture storage (ΔSMS), groundwater storage (ΔGWS), snow water equivalent (ΔSWE), and surface water storage (ΔSWS) based on the covariance information obtained from the Community Atmosphere Biosphere Land Exchange (CABLE) and the PCRaster Global Water Balance (PCR-GLOBWB) models. Evaluation with different ground measurements and satellite products between 2002 and 2019 exhibits significantly improved accuracy in all individual ΔTWS components. This improvement is of particular note in ΔGWS and ΔSWS, where the LSC approach increases the globally averaged correlation values by approximately 0.13 and 0.05, respectively. Reliable prior knowledge leads to a more accurate ΔTWS component estimate, and the use of ensemble-mean knowledge yields the best result.
Water Policy
Agriculture productivity is regularly affected by floods and droughts, and the severity is likely... more Agriculture productivity is regularly affected by floods and droughts, and the severity is likely to increase in the future. Even if significant efforts are spent on water development projects, ineffective project planning often means that they continue to occur or are only partly mitigated, for example, in the Mun River Basin, Thailand, where 1,000 s of water projects have been implemented. Despite this, the basin regularly experiences floods and droughts. In this study, an analysis of the adverse impacts of basin-scale floods and droughts on rice cultivation in the Mun River Basin is conducted, and an estimation of the coping capacity of existing measures. The results demonstrate that while the total storage capacity of in-situ and ongoing projects would be sufficient to tackle both hazards, it can only be achieved if the projects are effectively utilised. Based on this, proposed solutions for the region include small farm ponds, a subsurface floodwater harvesting system, and oxbo...
Climate variability, trends, and their impacts on rice yields
Integrated Flood and Drought Mitigation Measures and Strategies
x actual average yield). However, if the rising trends in minimum and maximum temperatures persis... more x actual average yield). However, if the rising trends in minimum and maximum temperatures persist, there is a high possibility that the yield losses will become more severe in the future. Next, the identification of flood and drought-prone areas is executed. The inundated areas at 10, 25, 50, and 100-year return period are obtained from an integrated hydrologic (SWAT) and hydraulic (HEC-RAS) model. The flooded areas are larger on the left bank than the right and that the flood depths vary from 0-4 m. About 60% of the floodplain inundation is less than 1 m and mostly found at the upstream and central areas of the river. The flat terrains make flooding duration last long, causing damage to crop growth and yields, particularly rice, which occupies a majority of the area and mostly locates on the river banks. Drought-prone areas are detected by using the proposed comprehensive drought risk assessment scheme that incorporates hazard, exposure, and vulnerability. The hazard is estimated from water deficits calculated with respect to rice water requirement. Exposure is based on population and rice field characteristics, while other physical and socioeconomic factors and coping capacity are used in the estimation of vulnerability. The findings demonstrate that drought hazard is most critical in October, which can reduce rice yields significantly. Rice fields in the central part are more exposed to droughts than in other areas. Extensive land is under high and moderate vulnerability. The higher drought risks emerge in October and November and decrease from north to south. After flood and drought problems are identified, a coping capacity of existing and ongoing water resources development projects are evaluated. The total storage capacity of those projects is sufficient to cope with both hazards, but the performance is inefficient and ineffective. Thus, several pieces of advice are provided to improve the performance of in-situ measures. Moreover, other measures are proposed to complement the existing measures and make the storage system more flexibility. The suggested measures are practicable, applicable, economical, and less environmental impacts. They have the potential to sustainably solve both floods and droughts in order to enhance rice production in the basin. This study provides all dimensions associated with floods and droughts, their impacts on rice yields, and mitigation measures to tackle both hazards simultaneously and sustainably. The achievement over the two climate extremes will ensure adequate food availability and alleviate poverty in the basin. Furthermore, the study shows that a holistic approach to simultaneously solving both problems is efficiency as all drops of water are utilized to benefit agriculture, the primary sector that feeds a growing population. 1 General introduction 1.1 Floods and droughts 1.1.1 Flooding 1.1.2 Drought 1.2 Impacts on agriculture 1.3 Research gaps 1.4 Selection of the study area and scope of the study 1.5 Research objectives 1.6 Outline of the thesis References 2 Chapter 1 1.1 Floods and droughts Floods and droughts are the two main meteorological catastrophes. Flooding occurs the most (33%), whereas droughts are less frequent (5%-Table 1-1), but cause more fatal impacts in terms of the number of the death toll. Combined, the hazards account for 80% of the total number of people affected by natural disasters (Table 1-2). Furthermore, they have created enormous environmental, social, and economic impacts, such as degraded wetland areas, diminished natural biodiversity, destroyed agricultural land and industrial facilities, and high economic costs. It is expected that climate change effects (i.e., more intense rainfall, increasing seawater levels, etc.) will exacerbate flood occurrences and impacts in the future (
Development of an integrated flood hazard assessment model for a complex river system: a case study of the Mun River Basin, Thailand
Modeling Earth Systems and Environment
Flooding is the most frequent natural disasters in Thailand, resulting in the loss of life and da... more Flooding is the most frequent natural disasters in Thailand, resulting in the loss of life and damage. In this research, we develop an integrated hydrologic and hydraulic model of the Mun River Basin, Thailand, and employ it to predict flood hazard maps at 10-, 25-, 50-, and 100-year return periods. The ‘goodness-of-fit’ statistics for probability distributions of rainfall data are investigated to select the best-fit distribution, which is used to derive the design rainfall depths for the scenarios (10-, 25-, 50-, and 100-year return periods). The results highlight the diversity of probability distributions even in the basin scale. The model demonstrates satisfactory results, and the flood hazard maps reveal that the extent of flooding is greater on the left bank than the right, and that the flood depths vary mostly between 0 and 4 m. The results also demonstrate that approximately 60% of floodplain inundation is < 1 m, which is mostly observed at the upstream and central areas of the river. The extent of flooding downstream is not as large as the upstream, but generally deeper. Due to the flat topography, the duration of flooding is long, which could damage crop growth and yield, including cities in the flooded areas. This information is essential for the government and authorities to develop flood-control measures and flood management strategies. In this case, planning and regulation of the use of land, and levees to protect the exposed cities are recommended. The integrated model can be further developed for the design of flood mitigation measures and flood forecasting and warning systems. The approach and parameters (both initial and calibrated ranges) can be used to guide future model development and in other basins with similar catchment characteristics, particularly where gauge data are not available.
Assessment of drought hazard, exposure, vulnerability, and risk for rice cultivation in the Mun River Basin in Thailand
Natural Hazards
When assessing drought risk, most studies focus on hazard and vulnerability, paying less attentio... more When assessing drought risk, most studies focus on hazard and vulnerability, paying less attention to exposure. Here, we propose a comprehensive drought risk assessment scheme combining hazard, exposure, and vulnerability. At the Mun River Basin, 90% of rice cultivation is rain-fed and regularly encounters droughts resulting in the lowest yields in the country. The water deficit calculated with respect to rice water requirement is used to assess drought hazard and is estimated at monthly time steps. We use drought severity and frequency for hazard estimation and population and rice field characteristics for exposure. Vulnerability is represented by physical and socioeconomic factors and coping and adaptive capacity. Between 1984 and 2016, monthly precipitation during the rice-growing season was insufficient to meet rice water needs at all growth stages (July–November). The hazard is more severe in October and November, which can lead to significantly reduced yields. People and rice fields in the center part of the basin are more exposed to drought than in other parts. Extensive areas are under high and moderate vulnerability due to low coping capacity. The higher drought risks appear in the last 2 months of the growing season and decrease from north to south, while the risk map of total precipitation demonstrates that most of the areas have low and very low risk. This emphasizes the importance of monthly time series analysis to calculate agricultural drought hazard and risk. Consequently, we recommend using the hazard and risk maps for October and November instead of the total precipitation to develop solutions to improve rice yield.
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Papers by Saowanit Prabnakorn