Chao Phraya Research Articles

Length-Weight Relationship and Condition Factor of Fishes in Two Major Rivers, the Chao Phraya and the Bang Pakong, in Thailand.

Length-weight relationship (LWR) was used as a tool to assess the status of fish stocks, through condition factor, in major rivers in Thailand. Fifty-one fish species from each river, i.e., The examined for LWR using 11 years of monitoring data (2010-2020) for Bang Pakong and 14 years of monitoring data (2007-2020) for Chao Phraya, which comprised 57,871 samples. The parameters for LWR and condition factor were examined by species and by body shape, i.e., ovate, oblong, elongate or eel-like. The coefficient of determination (r 2 ) of all log-transformed LWRs was greater than 0.90. Parameter b of LWR ranged between 2.06 and 3.46 (median = 3.00) for fishes from the Chao Phraya River and between 1.72 and 3.68 (median = 2.76) for fishes from the Bang Pakong River. The overall condition factor, which implies the well-being that indicates the health or fattening of the fishes in a stock, ranged between 0.93 and 1.09. There was no significant difference in the overall well-being (P = 0.279) between the two rivers. Fishes with oblong and elongate shapes in the Chao Phraya River showed higher median values of parameter b of LWR than those from the Bang Pakong River. However, there was no significant difference (P > 0.05) in the well-being of the fish stocks between the two rivers when pooled by shape. The findings are fundamental information for fish stock assessment in the two rivers, which greatly support the small-scale fisheries in Thailand.

Re–operating the Bhumibol and Sirikit Dams Using Hybrid Neuro–Fuzzy Technique to Solve the Water Scarcity and Flooding Problems in the Chao Phraya River Basin

The decision support system to reservoir re–operation using Artificial Intelligence has been broadly studied and proven in term of the operational performances for both single and multiple reservoir system, this study applied Adaptive Neuro Fuzzy Inference System (ANFIS) technique for reservoir re–operation in Chao Phraya River Basin aiming to reduce water scarcity and flooding problems in the central region of Thailand. ANFIS is an integrated approach in which neural networks are utilized to enhance the fuzzy inference system and create fuzzy “IF–Then” reservoir operational guidelines with proper membership functions for reservoir re–operation. In this study, ANFIS operating rules were trained using two different datasets; long–term dataset (scenario 1) and water year–based dataset (scenario 2). It is revealed that the extent of yearly water deficit in critical dry years are totally reduced to nearly zero when re–operating with ANFIS operation rules, except in the year 2012. However, the yearly water deficit in year 2012 is also substantially reduced from 504 MCM by the current operation to 127 and 119 MCM for scenario 1 and scenario 2, respectively when two scenarios of ANFIS–based reservoir re–operation model were performed. Moreover, considerable total amount of spilled water from BB and SK Dams is definitely declined to 0 and 37 MCM in years 2002 and 2011, respectively when water year–based ANFIS model was implemented. In addition, it is expressed that average water storages of two main dams obtained from two scenarios of ANFIS model are substantially increased up to +6.08% and +6.94% for BB Dam and +0.09% and +1.62% for SK Dam in comparison with the current operation. This signifies that supplying water from dams to meet the target water demand through adaptive fuzzy–rules can be well handled and flooded water can be minimized.

Effects of environmental impacts on the distribution and morphometric characteristics of Rehderiella parva (Lea, 1856) (Gastropoda: Hydrobiidae) and the gastropod communities of the Chao Phraya River (Thailand )

Effects of environmental impacts on the distribution and morphometric characteristics of Rehderiella parva (Lea, 1856) (Gastropoda: Hydrobiidae) and the gastropod communities of the Chao Phraya River (Thailand )

Predicting the Potential Distribution Areas of the Asian Redtail Catfi sh (Hemibagrus wyckioides Fang and Chaux, 1949) in the Chao Phraya River, Thailand, using Maximum Entropy Modelling

Hemibagrus wyckioides is recognized as an economically important freshwater fi sh in Thailand. However, there are no available comprehensive data regarding the geographic distribution and habitat suitability of H. wyckioides in Thailand. In addition, its natural population has tended to continuously decrease. This study aimed to predict the suitable distribution areas of H. wyckioides in the Chao Phraya River, Thailand, using the maximum entropy (MaxEnt) algorithm based on climatic factors, including 11 temperature and 8 precipitation indices from the WorldClim database. Model performance was evaluated by the area under the receiver operating characteristic curve (AUC). The jackknife test was used to assess the contribution of each variable to the model. The results revealed that the MaxEnt model performed acceptably well, with an AUC value of 0.939, representing excellent accuracy in predicting the appropriate distribution areas of H. wyckioides in the Chao Phraya River. The potential distribution areas of H. wyckioides were observed mostly along the Chao Phraya River in Sing Buri and Ang Thong Provinces. According to the results of the jackknife test, 11 climatic variables impacted the distribution of H. wyckioides. The annual mean temperature (BIO1), precipitation of driest month (BIO14), and annual temperature range (BIO7) were the most important infl uencing variables, with impact values of 53.5%, 15.9%, and 11.9%, respectively. Therefore, understanding the potential distribution areas can assist researchers in monitoring, management, and conservation activities or with the development of new natural protected areas of H. wyckioides in high-quality areas in the Chao Phraya River.

Mathematical forecasting simulation of salinity intrusion in Chao Phraya River

At present, at two water stations along Chao Phraya River, the main river of the central region of Thailand, the salinity in the river exceeds the raw water salinity standard for tap water production that must be lower than 0.25 g/L. During December to May, since 2013, the salinity value exceeded the raw water standard, strongly affecting the raw water management of Metropolitan Waterworks Authority. Surveillance and prediction of salinity level at the river mouth at Klong Lat Pho Water Quality Monitoring Station, downriver from Sam Lae station, in advance, will be beneficial to the Metropolitan Waterworks Authority’s raw water management. The purpose of this study was to forecast the hourly salinity levels at Khlong Lat Pho Water Quality Monitoring Station. The methods used were Exponential Smoothing and Winter’s Linear and Seasonal and Exponential Smoothing (EXPOW). Both forecasting methods showed a very low mean of square error (MSE): 0.1551 when the exponential smoothing method was used with alpha= 0.9995 and 0.4869 when the EXPOW was used with alpha = 0.0618, gamma = 0.9995, and beta = 0. 0001. Nevertheless, the exponential smooth method fell out of favor since, for long-term prediction, its predicted value converged to a constant value, 0.2405, useless for predicting seasonal variation. On the other hand, the EXPOW method, even though less effective in terms of MSE, produced more reliable short and long-term forecasts for salinity at Khlong Lad Pho Water Quality Monitoring Station.

Exploring PFOA adsorption isotherm in the presence of NOM using DBD plasma-modified GAC

Perfluorooctanoic acid (PFOA), a widely used perfluorinated alkyl substance (PFAS), poses significant environmental and health risks. This study investigates PFOA adsorption in the existence of natural organic matter (NOM) using granular activated carbon (GAC) modified with dielectric barrier discharge (DBD) plasma. PFOA’s amphiphilic structure, characterized by a hydrophilic carboxyl group head and a hydrophobic perfluorinated tail, contributes to its versatility and persistence. The selection of the Chao Phraya River (CPR) water as the NOM source, captures the complexity of a major water body subjected to diverse pollution sources. The results were analyzed through the Toth and Temkin isotherm models. Application of the Toth isotherm model reveals enhanced PFOA adsorption capacity in CPR water compared to DI water, emphasizing the influence of NOM. The Temkin isotherm analysis further characterizes the strength and efficiency of the adsorption process, highlighting a stronger interaction between PFOA and plasma-modified GAC in CPR water. The study indicates that the adsorption process in CPR water may be more influenced by PFOA surface coverage on the GAC surface in the presence of NOM. Overall, this research contributes valuable insights into pollutant removal strategies, highlighting the potential of DBD plasma-modified GAC in addressing PFOA contamination challenges in water systems.

Influence of tidal phenomena on nutrient variations in water column of the Chao Phraya River estuary

Influence of tidal phenomena on nutrient variations in water column of the Chao Phraya River estuary

Integration of Adaptation Measures Responding to Hydrological Hazards for Chao Phraya River Basin, Thailand, in Comparison with Cases from Jiulong River Basin, China

Integration of Adaptation Measures Responding to Hydrological Hazards for Chao Phraya River Basin, Thailand, in Comparison with Cases from Jiulong River Basin, China

A Half-Century of Human Impact on Nan River Runoff and Sediment Load Supplied to the Chao Phraya River

The construction of large dams in the upper tributary basin of the Chao Phraya River (CPR) has been linked to a significant decrease in sediment load in the CPR system, estimated between 75–85%. This study, utilizing historical and recent river flow and sediment data from 1922 to 2019, examines the impact of three major dams constructed in the Nan River basin (the Sirikit, Naresuan, and Khwae Noi dams) on river runoff and sediment loads in the CPR. The investigation employed the Mann–Kendall (MK) test and the double mass curve (DMC) for analysis. Findings indicate that the Nan River is a major contributor to the CPR, accounting for around 40% of the runoff and 57% of the total sediment load (TSL). The Naresuan diversion dam’s water regulation was found to significantly reduce annual runoff and TSL downstream of the dam. Despite an initial increase in sediment load at the CPR headwater (C.2) post the construction of the Sirikit dam, attributed to expanded irrigation downstream and channel improvements in the lower Nan River, the operation of the three dams eventually led to a 31% reduction in sediment load at C.2 compared to pre-construction levels.

Assessing extreme flood inundation and demographic exposure in climate change using large ensemble climate simulation data in the Lower Chao Phraya River Basin of Thailand

Study regionLower Chao Phraya River Basin (LCPRB), Thailand. Study focusThis study aims to make a robust assessment based on a large ensemble d4PDF dataset and a flood-inundation model Inundation Model Coupling Rainfall-runoff (IMCR) for the LCPRB. Inundation area and depth for 100-year flooding are evaluated for the flood volume of capacity greater than 2000 m3/s for both past (1951–2010) and future (2051–2100) climates. This study also evaluates the affected population exposure in the region for both past and future climate scenarios. New hydrological insights for the regionThe IMCR inundation simulation findings indicate that compared to the historical climate, the inundation area increases by an average of 1.0–1.4 times, and the critical area (depth >3 m) increases by an average of 1.1–1.3 times. On the other hand, the exposed population in the future, with respect to the SSP5 scenario "Taking the Highway," is expected to decrease on average by 0.7–0.9 times in comparison to the past climate for depth > 0 m. However, keeping the population constant as in the past, the exposed population is likely to increase on average by 1.3–1.4 times in comparison to the past climate for depth > 0 m.

Performance Evaluation of Rainfall-Runoff Models for Predictions of Inflows to Bhumibol Reservoir in Thailand

The Bhumibol reservoir in the Ping River basin is the largest reservoir in the Kingdom of Thailand. This reservoir has contributed to economic development of the country by supplying increased electricity and irrigation water demands as well as flood mitigation in riparian areas along the Ping and the Chao Phraya River. The prediction of inflows to the reservoir is crucial for the optimal management of water for irrigation, power generation and flood control. Properly customized rainfall-runoff models of the catchment could provide the basis for predicting the inflows to the reservoir. Hence, five lumped conceptual rainfall-runoff models were developed for the Ping River basin to simulate daily inflows to the Bhumibol reservoir. The rainfall-runoff models are Australian Water Balance Model (AWBM), Sacramento Soil Moisture Accounting Model, Simplified Hydrolog Model (SIMHYD), Soil Moisture Accounting and Routing Model (SMAR) and Tank Model. The evaluation of the performances of these models showed that all models are capable of predicting inflows. However, the SIMHYD, Sacramento, AWBM and Tank models perform better than SMAR model. Hence, these models could be employed for prediction of inflows to the reservoir with acceptable accuracy.

Hydrochemical characteristics and salt intrusion in groundwater of the lower Chao Phraya river basin: Insights from stable isotopes and hydrochemical analysis

Saltwater intrusion is a significant hydrogeological challenge in coastal regions. This study investigates salt intrusion and hydrogeological processes in the Lower Chao Phraya River basin using stable isotopes and hydrochemical analysis. One Hundred groundwater wells sampled from different aquifers were analyzed for major ions spanning from 2010 to 2021, as well as stable isotopes specifically for the samples in the year 2021. The results reveal four distinct groundwater types: Ca(HCO3)2, NaHCO3, NaCl, and CaSO4, based on their predominant cations and anions. Shallow groundwater, which represents the discharge zone affected by salt intrusion, halite dissolution, and cation exchange reactions, exhibits a significant concentration of NaCl. Water-rock interactions play a crucial role in shaping groundwater chemistry, with carbonate dissolution and precipitation dominating the Ca(HCO3)2 type and silicate weathering influencing the CaSO4 type. The NaHCO3 type is associated with ion exchange and seawater intrusion. Silicate and carbonate rock weathering are the dominant processes in the region. Stable isotope analysis indicates that groundwater recharge primarily comes from rainfall and surface water, with limited contributions from deep sources. Overall, this study provides valuable insights into the hydrochemical characteristics and complex water-rock interactions within the groundwater system of the Chao Phraya River basin. As a result, it holds significant potential for informing effective groundwater management practices and facilitating resource planning in the region. Furthermore, the findings and methodologies presented here offer valuable lessons for addressing saltwater intrusion and hydrogeological challenges in other coastal regions worldwide.

Enhancing Urban Flood Resilience: The Role and Influence of Socio-Economics in the Chao Phraya River Basin, Thailand

Enhancing Urban Flood Resilience: The Role and Influence of Socio-Economics in the Chao Phraya River Basin, Thailand

Evaluating the necessity of post-processing techniques on d4PDF data for extreme climate assessment.

The occurrence and severity of extreme precipitation events have been increasing globally. Although numerous projections have been proposed and developed for evaluating the climate change impacts, most models suffer from significant bias error due to the coarse resolution of the climate datasets, which affects the accuracy of the climate change assessment. Therefore, in this study, post-processing techniques (interpolation and bias correction methods) were adopted on the database for Policy Decision Making for Future Climate Change (d4PDF) model for extreme climatic flood events simulation in the Chao Phraya River Basin, Thailand, under + 4-K future climate simulation. Due to the limited number of the rain gages, the gradient plus inverse distance squared interpolation method (combination of multiple linear regression and distance weighting methods) was applied in this study. In the bias correction methods, the additional setting of monthly and seasonal periods was adjusted. The proposed bias correction approach deployed gamma distribution combined with generalized Pareto distribution setting with the seasonal period for the rainy season datasets, whereas only the gamma setting was applied with the monthly period during the dry season. The outcomes revealed that the proposed method could react to extreme rainfall events, expand dry days during dry season, and intensify rainfall amount during rainy season. The post-processing d4PDF trends of six sea surface temperature (SST) patterns (consists of 90 ensemble members) of two periods (near future: 2051-2070 and far future: 2091-2110) recorded the highest and lowest amounts of annual rainfalls of 4,450 mm/year in mid-stream of Nan River and 710 mm/year in the lower CPRB, respectively. Notably, the significant variances noted in the rainfall patterns among ensembles, demanding further investigation in future climate change, impact studies. The findings of the study provided novel insights on the importance of proper post-processing techniques for improving the robustness of d4PDF in climate change impacts assessment.

Thailand Raw Water Quality Dataset Analysis and Evaluation

Sustainable water quality data are important for understanding historical variability and trends in river regimes, as well as the impact of industrial waste on the health of aquatic ecosystems. Sustainable water management practices heavily depend on reliable and comprehensive data, prompting the need for accurate monitoring and assessment of water quality parameters. This research describes a reconstructed daily water quality dataset that complements rare historical observations for six station points along the Chao Phraya River in Thailand. Internet of Things technology and a Eureka water probe sensor is used to collect and reconstruct the water quality dataset for the period from June 2022–February 2023, with Turbidity, Optical Dissolved Oxygen, Dissolved Oxygen Saturation, Spatial Conductivity, Acidity/Basicity, Total Dissolved Solids, Salinity, Temperature, Chlorophyll, and Depth as the recorded parameters from six different stations. The presented dataset comprises a total of 211,322 data points, which are separated into six CSV files. The dataset is then evaluated using the Long Short-Term Memory (LSTM) algorithm with a Mean Squared Error (MSE) of 0.0012256, and Root Mean Squared Error (RMSE) of 0.0350080. The proposed dataset provides valuable insights for researchers studying river ecosystems, supporting informed decision-making and sustainable water management practices.

A new species of furry crown crab, Limnopilos Chuang & Ng, 1991 (Brachyura, Hymenosomatidae) from Tonle Sap, Cambodia

Abstract A new species of the wholly freshwater hymenosomatid crab genus Limnopilos Chuang & Ng, 1991, is described from Tonle Sap River in the lower Mekong drainage, Cambodia. This is the fourth species known, and the second one from Indochina. The type species, of Limnopilos, L. naiyanetri Chuang & Ng, 1991, was from the Chao Phraya drainage to the west in central Thailand. The new species is characterized by the presence of a rostrum, relatively shorter ambulatory legs and a different structure of the male first gonopod. Limnopilos sumatranus Naruse & Ng, 2007, is also recorded from southern Peninsular Malaysia for the first time.

Variation of mercury in 4 major estuaries in the Gulf of Thailand during wet season

The Mae Klong River (MK), Tha Chin River (TC), Chao Phraya River (CP), and Bang Pakong River (BPK) are recognized as critical conveyors of terrestrial substances, including pollutants, into the Inner Gulf of Thailand (Inner GOT). This study sought to explore the presence of mercury (Hg), a highly toxic and bioavailable pollutant, in both water and surface sediment at the mouths of the four rivers in pre- and post-wet season (WS). The results revealed that the total mercury (T-Hg) concentrations in the water ranged from 10 ng/L (TC) to 125 ng/L (CP) in pre-WS and 17 ng/L (MK) to 1011 ng/L (TC) in post-WS. Notably, the post-WS concentrations of T-Hg were relatively higher than the pre-WS, with an average concentration of particulate Hg (P–Hg) increasing by approximately 3–5 times. Consequently, the average P–Hg proportion to T-Hg of each estuary in the post-WS was comprised of greater than 67%. Moreover, a correlation was observed among salinity, total suspended solid (TSS) and particulate Hg (P–Hg). Similarly, the estuarine sediment, excluding MK, exhibited a higher average concentration of T-Hg during the post-WS period. The average T-Hg concentration in sediment ranged from 17 (BPK) to 119 (MK) μg/kg in pre-WS and 15 (MK) to 140 (CP) μg/kg in post-WS. The presence of organic matter (total organic carbon or TOC content), and clay-sized particles were identified as potential factors influencing the concentration of T-Hg in the sediment. In addition, a higher positive correlation was observed between T-Hg and silt-sized particles in BPK. In this study, both T-Hg in the water column and T-Hg in sediment increased during the post-WS period, suggesting that Hg transportation from sources to river mouths during WS were intensified. Furthermore, the correlation between T-Hg and fine-grained particle, as well as the greater T-Hg levels in the estuarine sediment, indicates that Hg may be transported from rivers to the offshore marine environment via the fine-grained fraction.

Can 210Pb be used as a paleo-storm proxy?

There is increasing interest within the scientific community, as well as the public, to determine if tropical cyclones are increasing in frequency and/or magnitude because of climate change. Unfortunately, the instrumental weather record only extends over the last 100–150 years depending upon location. It is thus desirable to develop paleo-storm proxies to extend the tropical cyclone record to hundreds, if not thousands, of years. Overwash sand deposits, sediment grain size, and various geochemical parameters (e.g., δ13C, δ15N, C/N) have been applied successfully for coastal lake sediments. We present here another potential proxy candidate, the natural radionuclide 210Pb. With a 22.2-year half-life, 210Pb age dating is often used to calibrate other proxies over essentially the same period as the instrumental storm record. We hypothesize here that trends in the 210Pb profiles, in addition to providing chronological information, can provide independent records of storm deposits in some situations. To illustrate how 210Pb may serve as an additional storm proxy, we present data from sediment cores collected from the Chao Phraya Delta (Upper Gulf of Thailand), an area characterized by a rapidly retreating shoreline. Some of the 210Pb profiles mark sedimentary layers with anomalously low excess 210Pb activities interspersed between layers with significant excess activities. We suggest that these layers may result from rapid deposition offshore of older storm-eroded shoreline material. The estimated ages of these 210Pb-deficient layers match, within estimated uncertainties, years when typhoons or tropical storms are reported to have severely eroded the nearby Thai coastline. The matching of the time scales of 210Pb and recorded tropical cyclones, both about 100–150 years, allows this approach to be used to explore for storm deposits and tune geochemical and other proxies for extended study over time scales of several decades or longer.

Monitoring of nature-based solution for stabilizing eroded muddy coastline of the Chao Phraya Delta, Thailand

The Chao Phraya Delta (CPD), Thailand’s largest delta and low-lying muddy coast, has experienced shoreline recession for over six decades due to relative sea-level rise. A nature-based solution, bamboo fences, widely used in low-lying tropical areas, have been intensely applied along the CPD coastline during the last two decades. This study evaluated the effectiveness of bamboo fences in protecting eroded CPD coastlines using remote sensing data (aerial photographs, satellite imagery, and LiDAR observation data). Results from this study indicate that the effectiveness of bamboo fences in trapping sediment decreased over time due to the deterioration of bamboo, which generally deteriorates within four years. Additionally, the installation of multiple layers of bamboo fences did not directly increase the effectiveness of the structure in stabilizing the CPD coastline. It was also found that the mangrove shoreline can be successfully regenerated in the CPD coast where the seabed is higher than 0.5 m amsl. Because of the short life of the bamboo fences, the bamboo fence may not be the best solution for coastal protection and sustainable coastal management in a low-lying area with a high rate of shoreline recession and a low rate of sedimentation.

Microplastics and heavy metals in a tropical river: Understanding spatial and seasonal trends and developing response strategies using DPSIR framework

Microplastics (MPs) have become an increasingly popular topic in recent years due to the growing concern about their impact on human health and the environment. Rivers in Southeast Asia are the dominant source of plastics and MPs into the environment; however, research on MPs in rivers from the region is insufficient. This study aims to investigate the impacts of spatial and seasonal variations on the distribution of MPs with heavy metals in one of the top 15 rivers releasing plastics into oceans (Chao Phraya, Thailand). Findings from this study are analyzed using the Driver-Pressure-State-Impact-Response (DPSIR) framework for proposing strategies to minimize plastic and MPs in this tropical river. Spatially, most MPs were detected in the urban zone, while the lowest was in the agricultural zone. Also, MP levels in the dry season are higher than at the end but lower than at the beginning of the rainy season. MPs with fragment morphology were mainly found in the river (70–78 %). Polypropylene was found with the highest percentage (54–59 %). MPs in the river were mostly detected in the size range of 0.05–0.3 mm (36–60 %). Heavy metals were also found in all MPs collected from the river. Higher metal concentrations were detected in the agricultural and estuary zones in the rainy season. Potential responses, including regulatory and policy instruments, environmental education, and environmental cleanups, were drawn from the DPSIR framework.