Basins In Thailand Research Articles

Climate change influences on the streamflow and sediment supply to the Chao Phraya River basin, Thailand

This study investigates the effects of climate change on the sediment loads of the Ping and Wang River basins and their contribution to the sediment dynamics of the lower Chao Phraya River basin in Thailand. The various climate models under different Representative Concentration Pathways (RCPs) scenarios are employed to project sediment loads in future. The findings indicate a significant increase in river flow approximately 20% in the Ping River (PR) and 35% in the Wang River (WR) by the mid-21st century and continuing into the distant future. Consequently, this is expected to result in sediment loads up to 0.33 × 106 t/y in the PR and 0.28 × 106 t/y in the WR. This escalation is particularly notable under the RCP 8.5 scenario, which assumes higher greenhouse gas emissions. Additionally, the research provides insights into the potential positive implications for the Chao Phraya Delta's coastal management. Without further damming in the Ping and Wang River basins, the anticipated rise in sediment supply could aid in mitigating the adverse effects of land subsidence and sea-level rise, which have historically caused extensive shoreline retreat in the delta region, particularly around Bangkok Metropolis. The paper concludes that proactive adaptation strategies are required to manage the expected changes in the hydrological and sediment regimes to protect vulnerable coastal zones and ensure the sustainable management of the Chao Phraya River Basin in the face of climate change.

Modeling Flood Susceptible Areas Using Deep Learning Techniques with Random Subspace: A Case Study of the Mae Chan Basin in Thailand

Flooding is a recurring global issue that leads to substantial loss of life and property damage. A crucial tool in managing and mitigating the impact of flooding is using flood hazard maps, which help identify high-risk areas and enable effective planning and management. This study presents a study on developing a predictive model to identify flood-prone areas in the Mae Chan Basin of Thailand using machine learning techniques, precisely the random sub-space ensemble method combined with a deep neural network (RS-DNN) and Nadam optimizer. The model was trained using 11 geographic information system (GIS) layers, including rainfall, elevation, slope, distance from the river, soil group, NDVI, road density, curvature, land use, flow accumulation, geology, and flood inventory data. Feature selection was carried out using the Gain Ratio method. The model was validated using accuracy, precision, ROC, and AUC metrics. Using the Wilcoxon signed-rank test, the effectiveness was compared to other machine learning algorithms, including random tree and support vector machines. The results showed that the RS-DNN model achieved a higher classification accuracy of 97% in both the training and testing datasets, compared to random tree (93%) and SVM (82%). The model's performance was also validated by its high AUC value of (0.99), compared to a random tree (0.93) and SVM (0.82) at a significance level of 0.05. In conclusion, the RS-DNN model is a highly accurate tool for identifying flood-prone areas, aiding in effective flood management and planning.

Simultaneous Confidence Intervals for Ratios of the Percentiles of the Delta-Lognormal Distribution

Statistical percentiles are extremely important and valuable measurement tools in various contexts. They offer significant advantages when it comes to estimating a wide range of values across different fields, making them essential in statistical analysis and research. This importance motivates researchers to study the construction of simultaneous confidence intervals for ratios of percentiles of the delta-lognormal distribution. This research introduces four distinct methods for constructing such confidence intervals: the fiducial generalized confidence interval, the Bayesian-based highest posterior density credible interval using Jeffreys prior, Jeffreys rule prior, and Uniform prior. All methods are subjected to evaluation and comparison through coverage probabilities and expected lengths in Monte Carlo simulations. The simulation study shows that, overall, the Bayesian-based highest posterior density credible interval works better and more accurately than the fiducial generalized confidence interval. To further validate the findings of the simulation study, these methods are applied to real-world daily rainfall data collected from a river basin in Thailand.

Application of SWAT Model for Assessment of Surface Runoff in Flash Flood Areas

In addition to changes in the amount of rain, changes in land use upstream are considered a factor that directly affects the maximum runoff flow in a basin, especially in areas that have experienced floods and flash floods. This research article presents the application of the SWAT model to assess runoff in areas that have experienced flash floods, in order to analyze the proportion of land use change to the maximum runoff. Study areas that experienced flash floods were in three basins in Thailand (Lam Saphung Basin, Phrom River Basin, and Chern River Basin Part 1, which is a sub-basin of the Nam Chi River Basin). This study analyzed two main factors that influenced runoff in the river basin by considering two simulation situations: (1) changes in land use affecting runoff assessed by considering land use maps in 2006, 2008, 2010, 2015, 2017, 2019, and 2021 when using rainfall data only in the year 2021 for all cases and (2) changes in the amount of rainfall influencing runoff by considering the rainfall records in 2006, 2008, 2010, 2015, 2017, 2019, and 2021 when using the land use data only in the year 2021 for all cases. The results of the study found that the SWAT model can be effectively applied to estimate annual runoff in areas that have experienced flash floods under eight parameters with R2 values of 0.74, 0.82, and 0.74 for the Lam Saphung River Basin, Phrom River Basin, and Chern River Basin Part 1, respectively. In addition, it was found that the proportion of land use changes that involved changes from forested areas to residential areas was the greatest from 2008 to 2010 in the Phrom River Basin and Chern River Basin Part 1. This resulted in an increase in the maximum runoff amounts of 77.78% and 46.87%, respectively. When land use was constant, it was found that the rainfall in 2010, which was the highest, also had the greatest impact on the runoff in all three areas.

Impact of Spatial Rainfall Scenarios on River Basin Runoff Simulation a Nan River Basin Study Using the Rainfall-Runoff-Inundation Model

This study aims to investigate the impact of spatial rainfall distribution scenarios from ground observation stations on runoff simulation using hydrological modeling specific to the Rainfall-Runoff-Inundation (RRI) model. The RRI model was applied with six different spatial distribution scenarios of input rainfall, including Inverse Distance Weight (IDW), Thiessen polygon (TSP), Surface Polynomial (SPL), Simple kriging (SKG), and Ordinary kriging (OKG), to simulate the runoff of a 13,000 km2 watershed, namely the Nan River Basin in Thailand. This study utilized data from the 2014 storm event, incorporating temporal information from 28 rainfall stations to estimate rainfall in the spatial distribution scenarios. The six statistics, Volume Bias, Peak Bias, Root Mean Square Error, Correlation, and Mean Bias, were used to determine the accuracy of the estimated rainfall and runoff. Overall, the Simple kriging (SKG) method outperformed the other scenarios based on the statistical values to validate with measured rainfall data. Similarly, SKG demonstrated the closest match between simulated and observed runoff, achieving the highest correlation (0.803), the lowest Root Mean Square Error (164.48 cms), and high Nash-Sutcliffe Efficiency coefficient (0.499) values. This research underscores the practical significance of spatial interpolation methods, such as SKG, in combination with digital elevation models (DEMs) and landuse/soil type datasets, in delivering reliable runoff simulations considering the RRI model on the river basin scale.

Combined use of graphical and statistical approaches for rainfall trend analysis in the Mae Klong River Basin, Thailand

Abstract The main purpose of this paper was to investigate the monthly, seasonal, and annual rainfall variability in the Mae Klong River Basin in Thailand using the Mann–Kendall (MK) test, Sen's slope method, Spearman's Rho (SR) test, and the innovative trend analysis (ITA) method. The monthly rainfall data of eight stations for the period 1971–2015 were used for trend analysis. Datasets with significant serial correlation were corrected by the trend-free pre-whitening (TFPW) approach for statistical methods. The MK test showed increasing rainfall trends for five out of eight stations in the dry season while 50% of stations indicated increasing trends in the wet season. On an annual scale, 75% of the stations exhibited increasing rainfall trends. The results of the SR test were in line with the MK test for seasonal and annual rainfall. The ITA method showed comparable findings with those of the statistical methods. For the entire basin, trend analysis found increasing rainfall on both seasonal and annual scales by all the tests. The findings of this study could benefit water supply and management, drought monitoring, agricultural production activities, and socioeconomic development in the Mae Klong River Basin in the future.

Integrated assessment of water–energy–food nexus: conceptual framework and application to the Ping River basin, Thailand

ABSTRACT Water, energy and food are the three foremost vital resources that need to be protected for human existence and sustainable development. The study develops an indicator-based framework for integrated assessment of the water–energy–food nexus at the river basin scale. The framework is designed to have three successive levels for the assessment. The proposed three-tiered assessment framework can aid concerned resources management authorities to evaluate the water–energy–food nexus and also to identify the action required to enhance resource productivities. The suitability of the framework is demonstrated through its application to the Ping River basin in Thailand.

Phyllodiaptomusparachristineae, a new species of copepod (Copepoda, Calanoida, Diaptomidae) from the floodplain of the lower Mekong River Basin in Thailand and Cambodia.

Phyllodiaptomus (Phyllodiaptomus) parachristineaesp. nov., a new diaptomid copepod, was collected from 30 sites in the lower Mekong River Basin floodplain in northeastern Thailand and nine sites in Cambodia. The new species is the 13th species of the genus to have been recorded across Asia. It has a wide range of habitats, occurring in small to large, temporary to permanent water bodies, and it can be found at any time of the year. The morphology of the new species is most similar to that of the males of P. (P.) christineae, having a comb on the antepenultimate segment on the right antennule, symmetrical caudal rami, a narrow hyaline lamella on the left P5 basis, a distal accessory spine on the right P5Exp-2, and a single-lobed Enp on the right P5. On the other hand, the males of the new species have second and third urosomites without hair-like setae on the ventral margin, a rounded distal margin of the P5 intersclerite plate, a semi-circular lamella on the right P5 basis, a strong principal lateral spine inserted at the proximal 1/3 of the right P5Exp-2, and a two-segmented left P5Enp. Morphological differences among species in the subgenus Phyllodiaptomus (Phyllodiaptomus) as well as the distribution and habitats of the 13 species and two subspecies of Phyllodiaptomus in Asia are discussed.

Projected seasonal changes in future rainfall erosivity over the Lancang-Mekong River basin under the CMIP6 scenarios

Climate change is a driver of soil erosion, but the future projections of seasonal rainfall erosivity variability and spatial distribution over the Lancang-Mekong River Basin (LMRB) are still not well understood. Based on the bias-corrected precipitation data from five General Circulation Models (GCMs) in the sixth phase of the Coupled Model Intercomparison Project (CMIP6), the impacts of future climate change on the seasonal rainfall erosivity over the LMRB were assessed using three widely applied empirical daily rainfall erosivity models under three combined scenarios of the Shared Socioeconomic Pathways and the Representative Concentration Pathways (SSP1-RCP2.6, SSP3- RCP7.0 and SSP5- RCP8.5). The results show that rainfall erosivity would generally increase in the near term (2030–2060) and far term (2070–2100), and more ensemble members agree with the increase in rainfall erosivity, especially under the high emission scenarios in the far term. In the near term, the ensemble mean of basin-wide rainfall erosivity would increase by 2.5%-8.7% compared to the baseline period (1980–2010), while in the far term, the ensemble mean would increase by 12.2%-31.0%. Seasonal variations in rainfall erosivity show that summer rainfall erosivity from June to August accounts for more than two-thirds of the total annual rainfall erosivity. Although the projected basin-wide average summer rainfall erosivity would increase, the mid-southern basin in Thailand and southern Lao PDR would experience a decrease. For rainfall erosivity from March to May, large areas except for the mountainous part of China would also experience a decrease in seasonal rainfall erosivity. The projected changes in rainfall erosivity can contribute to a better understanding of soil erosion risk under climate change across the LMRB.

The deterioration of groundwater quality by seawater intrusion in the Chao Phraya River Basin, Thailand

The Chao Phraya River Deltaic Plain is the largest basin in Thailand and the second largest one in Southeast Asia after the Mekong River Delta. In recent decades, the groundwater quality in the Lower Chao Phraya River Basin in Thailand has deteriorated due to salinization caused by seawater intrusion. In the present study, hydrogeochemical and statistical methods were employed to determine the hydrochemical characteristics of the groundwater and to investigate the possible sources of salinity in the study region for the years 2008 and 2020. In addition, samples were taken from precipitation, sea water, and river water to analyze their hydrochemical properties. Then, they were used as input in the "Simmr" code in the R programming language to model the hydrochemical conditions of the study area and their evolution over time. The results indicated that in the non-coastal regions, water-rock interaction (mineral weathering and ion exchange), and brine/connate water infiltration affected the quality of the groundwater. However, the seawater intrusion was limited only to the coastal regions. Furthermore, the groundwater quality deteriorated from 2008 to 2020. Finally, using stepwise regression in the R language, the salinity of the groundwater was simulated and compared with the measured salinity data. The results obtained by the stepwise model were in close agreement with those obtained from the hydrochemical studies. This study confirmed seawater intrusion in the coastal aquifer as well as the deterioration of groundwater quality over time. To slow down this process and to achieve sustainable conditions, groundwater extraction should be reduced in the study region.

A Dilemma between Flood and Drought Management: Case Study of the Upper Chao Phraya Flood-Prone Area in Thailand

Floods are the greatest natural disaster in Thailand, but they are an important part of recharging the water volume for groundwater resources. This paper focused on evaluating and discussing the relationship between flood magnitudes and flood management impacting groundwater storage in the Upper Chao Phraya River basin in Thailand, where the intensive rice production of the region is located. Based on satellite image data, there were annual flood inundations varying from 1950 to 10,470 km2 over the period 2005–2019. The evaluation shows those flooding events yielded floodwater recharge of approximately 0.5–5.9 km3. To lessen the flood damage, floodways with 2000 m3 s−1 of drainage capacity are proposed by the government. This measure aims to accelerate flood surplus out to the gulf of Thailand and to confine the flooding areas to a maximum value of 4650 km2. A reduction of approximately 3.4 km3 of groundwater storage is estimated if the floodways are implemented. Staple crops in the dry season, especially rice fields outside an irrigation project (rainfed area), cope with water stress. To sustain basin water demand in the dry season, approximately 1820 km2 should be allowed for an area flooded for a month where 0.9 km3 of water volume is harvested annually. Although flood control is important, potential impact on the reduction of groundwater recharge needs to be carefully considered. Therefore, a flood control policy shows the balance of available basin water occasionally supplied by the groundwater while rice water demand is being proposed.

Enhancing a Multi-Step Discharge Prediction with Deep Learning and a Response Time Parameter

Flood forecasting is among the most important precaution measures to prevent devastating disasters affecting human life, properties, and the overall environment. It is closely involved with precipitation and streamflow data forecasting tasks. In this work, we introduced a multi-step discharge prediction framework based on deep learning models. A simple feature representation technique using a correlation of backward lags was enhanced with a time of concentration (TC) concept. Recurrent neural networks and their variants, coupled with the TC-related features, provided superior performance with over 0.9 Nash–Sutcliffe model efficiency coefficient and substantially high correlation values for multiple forecasted points. These results were consistent among both the Upper Nan and the Loei river basins in Thailand, which were used as case studies in this work.

A disaggregated assessment of national water security: An application to the river basins in Thailand

Achieving water security is a global concern in the age of changing climate, population increase, urbanization, intensive socio-economic development, and land-use change. Addressing water security challenges is most appropriate at the river basin scale since hydrological boundaries at which water flows differ from administrative boundaries, and it can provide policymakers and decision-makers key insights to better support water management practices. This study carries out a disaggregated assessment of national water security by applying an indicator-based framework to evaluate water security conditions in all twenty-five river basins of Thailand from 2007 to 2015. The framework comprises five broad dimensions and eleven indicators. The study results revealed that the overall water security condition in Thai river basins has improved during this period. However, a fine-grained analysis at the dimensions and indicator level of water security shows that water productivity and the watershed health dimension are of concern in most river basins. The agricultural water productivity and the wastewater treatment capacity have deteriorated over the years in most basins. Likewise, it emerged that basins need to enhance their water resource management plans to account for future water challenges. The water security assessment framework presented in this study links well to the plans, policies, visions, and strategies developed for water resource management in Thailand. Thus, it can act as a decision-support tool to monitor the effectiveness of these plans and policies developed and arrive at interventions to enhance Thailand's water security.

Land–sea thermal contrast associated with summer monsoon onset over the Chao Phraya River basin

Earlier onset of the Southeast Asian summer monsoon (SAM) was observed over the Chao Phraya River basin in Thailand using Thai Meteorological Department-derived high-resolution merged rainfall data from 1981 to 2016. SAM variability depends on numerous local and global factors, including thermal conditions over the Bay of Bengal (BoB) and Tibetan Plateau (TbT). Despite tremendous past research efforts, the effect of thermal heat contrast on the SAM remains unclear. Using observational and reanalysis datasets, we found that the absolute value of total heat over the BoB was increasing. However, the interannual variability of total heat was greater over the TbT. Changes in surface temperature (± 1.5 °C), air thickness (± 20 m), and geopotential height over the TbT were associated with the timing of SAM onset. The results also suggested that significant changes in air thickness are driven by surface temperature differences over the TbT, while changes in the integrated apparent heat source and integrated apparent moisture sink of ± 100 W m−2 resulted in anomalous convective activities over the BoB and mainland of the Indochina Peninsula in years of early and late SAM onset. At the intraseasonal timescale, Madden–Julian oscillation (MJO) was observed over the Indian Ocean and Western Hemisphere for 4–10 days in years of early SAM onset. The opposite situation was found for years of late SAM onset, with MJO located over the Western Pacific Ocean and Maritime Continent.

Source tracing and chemical weathering implications of strontium in agricultural basin in Thailand during flood season: A combined hydrochemical approach and strontium isotope

87Sr/86Sr of river water are of great significance in constraining oceanic strontium (Sr) record and terrestrial climate change due to the connection of continental weathering and the adjacent ocean. This work presents the geochemical characteristics of dissolved Sr and hydrochemistry, and estimates chemical weathering rate together with elemental Sr flux during the flood season of the Mun River, the largest tributary of Mekong River. Hydrochemistry analysis indicates the dominance of Cl− and HCO3− for major anions with the average of 34.6 and 43.0 mg/L, respectively, and Na+ and Ca2+ together dominated the cationic composition with the average of 22.9 and 10.5 mg/L, respectively. The ion concentrations during flood season were lower than that in dry season, implying tremendous river runoff due to extreme rainfall. The dissolved Sr ranges 6.1–237.5 μg/L with higher contents in the upper Mun. Sr contents in flood season are lower and less fluctuated than that in dry season, whereas the divergence between up and downstream becomes larger. 87Sr/86Sr ranges 0.7100–0.7597, slightly higher than global average. Elemental molar ratio analysis partly corroborates the inference from correlation analysis, but 87Sr/86Sr does not correlate with Na/Ca, indicating additional influence except for the weathering of evaporites and silicates. Comparing to regional wastewater and rainwater, the lower reaches exhibits superimposed impact of agricultural inputs on weathering to dissolved loads, especially in downstream with more tributary convergence. Extreme rainfall during flood season and extensive agricultural production activities may interfere in altering riverine solutes. Silicate weathering rate and CO2 consumption rate are calculated as well as the yearly 87Sr in excess to the Mekong River and finally to the Pacific Ocean with a Sr flux of 1.98 × 103 tons/year, indicating significant influence on seawater strontium isotope evolution in the long run. Together with tropical climate and high-intensity precipitation, the accelerated chemical weathering process seems inevitable. Therefore, the impact of agricultural interference in the pan-Mekong River basin needs more systematic and multi-angle research to provide a comprehensive insight on better watershed management under tropical climatic conditions.

Comprehensive Assessment of Flood Hazard, Vulnerability, and Flood Risk at the Household Level in a Municipality Area: A Case Study of Nan Province, Thailand

Estimating flood hazard, vulnerability, and flood risk at the household level in the past did not fully consider all relevant parameters. The main objective of this study is to improve this drawback by developing a new comprehensive and systematic methodology considering all relevant parameters and their weighting factors. This new methodology is applied to a case study of flood inundation in a municipal area of Nan City in the Upper Nan River Basin in Thailand. Field and questionnaire surveys were carried out to collect pertinent data for input into the new methodology for estimating flood hazard, vulnerability, and risk. Designed floods for various return periods were predicted using flood simulation models for assessing flood risk. The flood risk maps constructed for the return periods of 10–500 years show a substantial increase in flood risk with the return periods. The results are consistent with past flood damages, which were significant near and along the riverbanks where ground elevation is low, population density is high, and the number of household properties are high. In conclusion, this new comprehensive methodology yielded realistic results and can be used further to assess the effectiveness of various proposed flood mitigation measures.

Challenges of Water Policy Involvement of the Community in the East Coast River Basin of Thailand

Water policy-making requires the dedicated involvement of all stakeholders, but difficulties remain for the community sector. This study aims to examine the critical challenges of community involvement in water policy decision-making in Thailand. Both qualitative and quantitative methods used in this research project consisted of 39 interviews with informants from a variety of interested parties and 403 community members from around the East Coast River Basin in Thailand completing a survey questionnaire. The results have shown that although mechanisms to enable community involvement in decision-making, such as public consultation and water-related committees, exist, problems remain within the community sector. The critical challenges lie in the opportunities of being consulted and the sharing of power in water policy-making. Although the networks are important, at the same time, they are also obstructing the community sectors in linking their requirements to a final decision, as well as dealing with politics, policy-makers, and staff who organized the process. Therefore, the government should further develop water committee mechanisms by setting up a comprehensive yet practically easy consultation process so that new or inexperienced community members get an opportunity to practice and learn the vital elements necessary in water policy-making. Further research should be conducted in order to compare the opportunities in water decision-making between communities in rural and urban areas. Studies at the local government level should be carried out, with results used as a mechanism to enable community involvement at higher levels of water policy decision-making.

A new species of copepod (Copepoda: Calanoida) from the floodplain of the lower Mekong River Basin in Thailand and Cambodia, with an amended diagnosis of the genus Dentodiaptomus Shen & Tai, 1964

A new species of copepod (Copepoda: Calanoida) from the floodplain of the lower Mekong River Basin in Thailand and Cambodia, with an amended diagnosis of the genus Dentodiaptomus Shen & Tai, 1964

Improving flood and drought management in agricultural river basins: an application to the Mun River Basin in Thailand

Abstract 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 oxbow lake reconnections. The suggested measures are practicable, economical, environmentally low-impact, and their implementation (if executed with appropriate care) would reduce flood and drought problems in the basin. Notably, the measures and calculation methods proposed for this basin can also be applied to other crops and regions.

Effective water quality and management for water user organizations by traditional rules and regulations of the local communities in the Chi River Basin in Thailand

Effective water quality and management for water user organizations by traditional rules and regulations of the local communities in the Chi River Basin in Thailand