Chiang Saen Research Articles

Past, present and future changes in the annual streamflow of the Lancang-Mekong River and their driving mechanisms

The rapid development of the Greater Mekong Subregion (GMS) makes it essential to understand the major mechanisms controlling the streamflow, especially for the Lancang-Mekong River (abbr. Mekong River). We used instrumental annual streamflow data (1960–2007) from Chiang Saen hydrological station and several gridded hydroclimatic datasets to explore the hydroclimatic evolution of the Mekong River, together with its driving mechanisms. We found that changes in the Mekong streamflow are consistent with precipitation changes, and the Mekong is thus a precipitation-dominated river that is susceptible to the effects of ongoing climate change. The instrumental record of Mekong annual streamflow is closely related to hydroclimatic changes, especially those related to moisture, within the area from the Hengduan Mountains to the Chiang Saen Station. Based on these gridded records, we extended the Mekong annual streamflow record to cover 1891–2021 using nested multiple linear regression fitting. The fitted streamflow explained up to 57.6 % of the instrumental changes and it indicates that the major 2019 drought was not unique over the past century. Despite extremely low precipitation and high temperatures, it is likely that the effects of drought can be mitigated via hydraulic engineering regulation. Climatological analyses showed that the Mekong annual streamflow is driven by the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), which is consistent with observed quasi-interannual cycles of 3–4 years. A multi-model ensemble of CMIP6 revealed that the Mekong annual streamflow will experience an upward trend in the future, accompanied by the more extreme impacts of ENSO and the IOD.

Rhodoferax potami sp. nov. and Rhodoferax mekongensis sp. nov., isolated from the Mekong River in Thailand.

Four newly discovered Gram-stain-negative bacteria, designated as BL00010T, BL00058, D8-11T and BL00200, were isolated from water samples collected at three hydrological monitoring stations (namely Chiang Saen, Chiang Khan and Nong Khai) located along the Mekong River in Thailand. An investigation encompassing phenotypic, chemotaxonomic and genomic traits was conducted. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that all four isolates represented members of the genus Rhodoferax. These isolates were closely related to Rhodoferax bucti KCTC 62564T with a similarity of 99.59%. The major fatty acids of the four novel isolates included C16:0 and C16:1ω7c and/or C16 : 1ω6c, whereas the major respiratory quinone was identified as ubiquinone Q-8. In addition, phosphatidylethanolamine was identified as a major polar lipid in these bacteria. The genomes of BL00010T, BL00058, D8-11T and BL00200 were similar in size (3.88-4.01 Mbp) and DNA G+C contents (59.5, 59.3, 59.5 and 59.3 mol%, respectively). In contrast to R. bucti KCTC 62564T and Rhodoferax aquaticus KCTC 32394T, the newly discovered species possessed several genes involved in nitrite and nitrile metabolism, which may be related to their unique adaptation to nitrile-rich environments. From the results of the pairwise analysis of average nucleotide identity of the whole genome and digital DNA-DNA hybridisation, it was evident that BL00010T and D8-11T represented two novel species, for which we propose the nomenclature Rhodoferax potami sp. nov., with the type strain BL00010T (TBRC 17198T = NBRC 116413T), and Rhodoferax mekongensis sp. nov., with the type strain D8-11T (TBRC 17307T = NBRC 116415T).

Superior performance of hybrid model in ungauged basins for real-time hourly water level forecasting – A case study on the Lancang-Mekong mainstream

In the context of climate change and human influence, timely and reliable information about water level variations is crucial for downstream flood control, navigation, and water resource management, particularly for the Lancang-Mekong River, the largest transboundary river in Southeast Asia. However, accurate real-time water level forecasts remain challenging, especially in data-limited regions. This study focused on the Chiang Saen Station, the uppermost Mekong River hydrological station, comparing three methods to predict 48-hour water levels: the Variable Infiltration Capacity (VIC) and Hydrology-Hydraulic (HH) physics-based models, the Gated Recurrent Unit (GRU) model, and hybrid models (VIC-GRU and HH-GRU). Evaluations were conducted at the 1-h, 3-h, 6-h, 12-h, 24-h, and 48-h forecast lead times. Assessments at various lead times showed that hybrid models incorporating physics-based mechanisms significantly enhanced predictions. VIC-GRU demonstrated superior performance, with KGE values surpassing 0.94, NSE values exceeding 0.95, MAE below 0.17 m, and PBIAS within ± 1 % across all lead times. Compared to GRU, PBIAS decreased by 84 %, while MAE dropped by 76 % to 81 % relative to VIC and HH, respectively. Notably, seasonal variations affected hybrid model performance, especially in the dry season. Optimal parameter selections enhanced model accuracy by 48 % to 49 %. These results underscore the potential of combining physics-based and deep learning models for more accurate, high-temporal-resolution real-time water level forecasts in data-scarce regions. A comprehensive study of streamflow characteristics enhances the advantages of this integration. This research contributes valuable insights to water level prediction in data-scarce regions and informs flood risk reduction and management in the Lancang-Mekong mainstream.

Elucidating potential bioindicators from insights in the diversity and assembly processes of prokaryotic and eukaryotic communities in the Mekong River

Drivers for spatio-temporal distribution patterns of overall planktonic prokaryotes and eukaryotes in riverine ecosystems are generally not fully understood. This study employed amplicon metabarcoding to investigate the distributions and assembly mechanisms of bacterial and eukaryotic communities in the Mekong River. The prevailing bacteria taxa were found to be Betaproteobacteria, Actinobacteria, and Bacteroidetes, while the dominant eukaryotic organisms were cryptophytes, chlorophytes, and diatoms. The community assemblages were influenced by a combination of stochastic and deterministic processes. Drift (DR) and dispersal limitation (DL), signifying the stochastic mechanism, were the main processes shaping the overall prokaryotic and eukaryotic communities. However, homogeneous selection (HoS), indicating deterministic mechanism, played a major role in the assembly process of core prokaryotic communities, especially in the wet season. In contrast, the core eukaryotic communities including Opisthokonta, Sar, and Chlorophyta were dominated by stochastic processes. The significance of HoS within prokaryotic communities was also found to exhibit a decreasing trend from the upstream sampling sites (Chiang Saen and Chiang Khan, Nong Khai) towards the downstream sites (Mukdahan, and Khong Chiam) of the Mekong River. The environmental gradients resulting from the site-specific variations and the gradual decrease in elevation along the river may have a potential influence on the role of HoS in community assembly. Crucial environmental factors that shape the phylogenetic structure within distinct bins of the core prokaryotic communities including water depth, temperature, chloride, sodium, and sulphate were identified, as inferred by their correlation with the beta Net Relatedness Index (betaNRI) during the wet season. Overall, these findings enhance understanding of the complex mechanisms governing the spatio-temporal dynamics of prokaryotic and eukaryotic communities in the Mekong River. Finally, insights gained from this study could provide information on further use of specific core bacteria as microbial-based bioindicators that are effective for the assessment and conservation of the Mekong River ecosystem.

The heterarchical life and spatial analyses of the historical Buddhist temples in the Chiang Saen Basin, Northern Thailand

Social hierarchy is the most prominent framework scholars use to examine settlement structure and development in Southeast Asia's pre- and post-state eras. The concept of social heterarchy, an unfixed ranked and diversified form of social structure, is an alternative approach to examining the sociopolitical organization of early settlements in the region. However, applications of heterarchy are limited in archaeological research on the sociopolitical organization and social landscape in Southeast Asian state societies. This paper incorporates space syntax and GIS angular and viewshed analyses to understand how sociopolitical interactions were arranged through the spatial configurations of the historical Buddhist temples in Chiang Saen, Thailand. This paper explores the complex interactions between various historical Chiang Saen social and religious groups through their temple spaces across time. Temple spatial characteristics indicate heterarchical forms of organization—evidenced by the hybrid and nonhierarchical temple spatial patterns characterized by open accessibility and integrated and symmetrical organization of spaces—co-existed with hierarchical relationships from the 13th to 17th century. The approach discussed here provides a better understanding of the multiscale relationships and interactions among sociopolitical groups in the historical communities in Chiang Saen, enabling a broader view that can embrace the co-occurrence of hierarchical and heterarchical forms of governance.

Sediment load crisis in the Mekong River Basin: Severe reductions over the decades

The boom in water infrastructure in the Mekong Basin has raised concerns over the annual supply of water and sediment among its riparian communities. By consolidating various datasets, continuous series of sediment load data were estimated for several stations located within the Lower Mekong Basin. At Chiang Saen in Thailand, the nearest station to the Chinese dams, the average sediment load was 79 ± 32 Mt./yr during the pre-dam period of 1965–1991. However, from 2010 to 2019 – during which a series of mega-dams were built in China – the sediment load decreased drastically by 84 % to only 12.5 ± 4.6 Mt./yr. This phenomenon of reduced annual sediment load during the mega-dam era (2010–2019) as compared to during the pre-dam era (1965–1991) can be observed at stations downstream from Luang Prabang (−53 %) to Nong Khai (−62 %) to Khong Chiam (−33 %).One of the drivers of this sediment load crisis is the rapid development of upstream dams. Especially after 2003, Chinese dams have reduced sediment supply to the downstream Mekong Basin severely. Concurrently, there was an increase in sediment contribution from the stretch of the Mekong River from Chiang Saen to Khong Chiam. A positive outcome of this increased sediment contribution was its buffering effect against the reduction in sediment load from the Chinese part of the Mekong Basin. Although sediment load at Kratie – the gateway station before the alluvial stretch comprising the Cambodian floodplains and Vietnam Mekong Delta – decreased from 78 ± 22 Mt./yr (1995–2009) to only 60 ± 21 Mt./yr (2010–2019), the reduction would have been higher without the increased sediment from the Chiang Saen – Khong Chiam stretch. However, with upcoming planned dams in Laos and Cambodia, this buffering effect is likely to be temporary, implying that the sediment load crisis as already experienced by the downstream communities can only become more severe.

Assessment of upbasin dam impacts on streamflow at Chiang Saen gauging station during the period 1960–2020 in the context of statistical studies

The Langcang-Mekong River Basin is the most important transboundary river basin in Asia. However, over the recent decades, dam construction has had increasingly profound effects on hydrological processes and aquatic, particularly riparian, ecosystems. Understanding these impacts is critical for the foundation of sustainable runoff surface management. In this study, different methods, based on both graphical and statistical techniques, were applied to assess the effects of the dams on annual, seasonal and monthly runoff and to detect hydroclimatic trends in the Upper Mekong Basin during the period 1960–2020. The results reveal two change points with respect to seasonal and annual flow regimes; that is, 2003 for the flood season and annual flows and 2013 for the dry season flow. The duration of the flood season and the volume of annual discharges have both significantly decreased since 2003 and the dry season discharge has significantly increased since 2013 (with both p-values <.05). The quantitative assessment suggests that, due to the effect of dams, the monthly discharges increased by 10–450 m3/s during the dry season (December–May), while the flood season's monthly flows decreased significantly, by 1,028–2,150 m3/s, from July to October at Chiang Saen station. The study of hydrological changes in the Mekong watershed is expected to be a significant contribution towards a better understanding of large watersheds in which the hydrological effects are influenced not only by climate change at large spatial and temporal scales but also by changes in the physical environment due to the construction of dams.

What can stage curves tell us about water level changes? Case study of the Lower Mekong Basin

Traditionally, morphological channel change is monitored using field observations such as cross-section measurements or bathymetry surveys. However, in basins with poor field data, it is difficult to monitor historical changes of the river channel. Using only water level and discharge data from the Lower Mekong Basin (LMB), we plotted the stage curves (graphs of water level against discharge values) at various stations from 1980 to 2019. These curves were subsequently analysed to calculate water level changes as a result of channel or discharge alterations.Our study area included stations in Thailand (Chiang Saen, Chiang Khan, Mukdahan), Laos (Pakse) and Cambodia (Kompong Cham, Chroy Changvar). Overall, decreases in wet-season water level were observed to be in the range of −0.89 m (Pakse) to −1.42 m (Kompong Cham) in 2010–2019 as compared to 1980–1989. While dry-season water level increased in Chiang Saen (+0.48 m), Chiang Khan (+0.81 m), Mukdahan (+0.37 m) and Pakse (+0.27 m) during the same period, decreases were observed at Kompong Cham (−0.13 m) and Chroy Changvar (−0.22 m). We also found that channel degradation has been the dominant process occurring at these stations during 2010–2019. Specifically, as compared to 1980–1989 records, channel incision has caused water levels in 2010–2019 to be lower by up to −0.17 m at Chiang Saen; Chiang Khan: −0.62 m; Mukdahan: −0.81 m and Pakse: −0.18 m. Concurrently, hysteresis was observed in the stage curves of Kompong Cham and Chroy Changvar. These plots of hysteresis suggest the presence of overbank flooding. We found that this hysteresis has been decreasing from 1980 to 2010, implying a reduction in flooding. This study represents a novel attempt to characterise channel change within the Mekong River using only historical water level and discharge data. Outside the Mekong basin, our methods can be applied to other basins where river cross-section data is scarce, and consequently, increase the analytical options available to researchers.

Comparison of CMIP5 and CMIP6 GCM performance for flood projections in the Mekong River Basin

Study regionMekong River Basin. Study focusThe Coupled Model Intercomparison Project Phase 6 (CMIP6) recently announced an updated version of general circulation models (GCMs). This study investigated the performance of improved CMIP6 over those of CMIP5 with respect to precipitation and flood representations in the Mekong River Basin (MRB). The correlation and error comparison from the referenced precipitation exhibited a significant improvement in the peak value representation. Hence, the impacts of climate change on future floods in the MRB were simulated and assessed using a distributed rainfall–runoff–inundation model. New hydrological insights for the regionThe results indicated that precipitation from CMIP6 had a higher correlation and a lower error coefficient than CMIP5. Similarly, the simulation of GCM ensembles of monthly discharge from CMIP6 exhibited a comparable average value to the observations, whereas CMIP5 underestimated the discharge simulations. The performance of the mean annual peak discharge improved from 37,220 m3/s (CMIP5) to 45,423 m3/s (CMIP6) compared to 43,521 m3/s (observation). The projections of future floods in the MRB from CMIP6 exhibited an increase of annual peak discharge at Chiang Saen, Vientiane, Pakse, and Kratie stations by 10–15%, 20–22%, and 24–29% for the SSP2-4.5 scenario, and 10–18%, 24–29%, and 41–54% for the SSP5-8.5 scenario in the near future (2026–2050), mid-future (2051–2075), and far future (2076–2100), respectively. The statistical K-S test showed significant changes in all stations and projected periods with a p-value < 0.01.

Wetland changes and their impacts on livelihoods in Chiang Saen Valley, Chiang Rai Province, Thailand

Wetland changes and their impacts on livelihoods in Chiang Saen Valley, Chiang Rai Province, Thailand

The Social Logic of the Temple Space: A Preliminary Spatial Analysis of Historical Buddhist Temples in Chiang Saen, Northern Thailand

The Social Logic of the Temple Space: A Preliminary Spatial Analysis of Historical Buddhist Temples in Chiang Saen, Northern Thailand

Impact of climate change on the spatio-temporal characteristics of meteorological and hydrological drought over the Lancang-Mekong River basin

Affected by global climate change, the status of meteorological and hydrological drought in the Lancang-Mekong River basin (LMRB) has witnessed great changes. Therefore, predicting the temporal and spatial variations of future drought as well as its propagation characteristics has become the basis for tackling climate changes and conducting cooperation on the water resources of the Mekong River. By applying the SWAT model and the method of atmosphere-land coupling, both the history (1960-2005) and the future (2022-2050 and 2051-2080) hydrological processes of the LMRB were simulated. Moreover, the future temporal and spatial variation trends of meteorological and hydrological drought were also predicted and analyzed by using the Standardized Precipitation Index and Standardized Runoff Index. The research results indicated that: ① In the future, the amount of precipitation will be increased. Thus, the meteorological drought will be alleviated to some extent, but at the same time, the inhomogeneous distribution of intra-annual precipitation and increased evaporation from the river basin together will cause a severer hydrological drought and an intense propagation process. ② Hydrological drought will have significant spatial heterogeneity. Specifically, the hydrological drought will be the most intense in Jinghong and Chiang Saen stations, followed by Luang Prabang, Mukdahan, and Pakse stations, and be the weakest in Vientiane station. ③ Over time, the frequency of hydrological drought in the river basin will be slightly decreased, but the proportion of heavy drought and severe drought will be increased, and the extreme drought will be enhanced both in amount and strength. Furthermore, the features of spatial variation will be more significant and noticeable.

River Discharge and Water Level Changes in the Mekong River: Droughts in an Era of Mega‐Dams

AbstractWhile 1992 marked the first major dam – Manwan – on the main stem of the Mekong River, the post‐2010 era has seen the construction and operationalisation of mega dams such as Xiaowan (started operations in 2010) and Nuozhadu (started operations in 2014) that were much larger than any dams built before. The scale of these projects implies that their operations will likely have significant ecological and hydrological impacts from the Upper Mekong Basin to the Vietnamese Delta and beyond. Historical water level and water discharge data from 1960 to 2020 were analysed to examine the changes to streamflow conditions across three time periods: 1960–1991 (pre‐dam), 1992–2009 (growth) and 2010–2020 (mega‐dam). At Chiang Saen, the nearest station to the China border, monthly water discharge in the mega‐dam period has increased by up to 98% during the dry season and decreased up as much as −35% during the wet season when compared to pre‐dam records. Similarly, monthly water levels also rose by up to +1.16 m during the dry season and dropped by up to −1.55 m during the wet season. This pattern of hydrological alterations is observed further downstream to at least Stung Treng (Cambodia) in our study, showing that Mekong streamflow characteristics have shifted substantially in the post‐2010 era. In light of such changes, the 2019–2020 drought – the most severe one in the recent history in the Lower Mekong Basin – was a consequent of constructed dams reducing the amount of water during the wet season. This reduction of water was exacerbated by the decreased monsoon precipitation in 2019. Concurrently, the untimely operationalisation of the newly opened Xayaburi dam in Laos coincided with the peak of the 2019–2020 drought and could have aggravated the dry conditions downstream. Thus, the mega‐dam era (post‐2010) may signal the start of a new normal of wet‐season droughts.

Ethnohistorical Archaeology and the Mythscape of the Naga in the Chiang Saen Basin, Thailand

AbstractThere is a northern Thai story that tells how the naga—a mythical serpent—came and destroyed the town known as Yonok (c. thirteenth century) after its ruler became immoral. Despite this divine retribution, the people of the town chose to rebuild it. Many archaeological sites indicate resettlement during this early historical period. Although many temple sites were constructed in accordance with the Buddhist cosmology, the building patterns vary from location to location and illustrate what this paper calls ‘nonconventional patterns,’ distinct from Theravada Buddhist concepts. These nonconventional patterns of temples seem to have been widely practiced in many early historical settlements, e.g., Yonok (what is now Wiang Nong Lom). Many local written documents and practices today reflect the influence of the naga myth on building construction. This paper will demonstrate that local communities in the Chiang Saen basin not only believe in the naga myth but have also applied the myth as a tool to interact with the surrounding landscapes. The myth is seen as a crucial, communicated element used by the local people to modify and construct physical landscapes, meaning Theravada Buddhist cosmology alone cannot explain the nonconventional patterns. As such, comprehending the role of the naga myth enables us to understand how local people, past and present, have perceived the myth as a source of knowledge to convey their communal spaces within larger cosmological concepts in order to maintain local customs and legitimise their social space.

Transnational Mobility and Utilization of Health Services in Northern Thailand: Implications and Challenges for Border Public Health Facilities.

Introduction/Objective:Transnational populations from the Association of Southeast Asian Nations are crossing borders regardless of whether their status is legal or undocumented, to receive health services in the border regions of Thailand. The implications and challenges of transnational mobility and the utilization of public health facilities in Thailand’s border regions are therefore investigated in this study.Methods:Four public health facilities were selected, located in 2 economically-active border areas in Northern Thailand: Mae Sai–Tachileik at the Thailand–Myanmar border and Chiang Saen–Ton Phueng at the Thailand–Lao PDR border. Qualitative data were obtained from in-depth interviews with 8 medical and non-medical hospital staff responsible for implementing facility-level policies and providing health services for the transnational population.Results:Five themes were identified through analysis of the implications and challenges for transnational mobility and the utilization of public health facilities under study: contextual determinants of illness in specific border areas; uncompensated care as opposed to financial management in serving the transnational population; health service opportunities for the transnational population; cross-border collaboration on public health; and the remaining challenges of transnational mobility in border regions.Conclusion:Conventional content analysis with interpretative induction of in-depth interview data offers recommendations for improving the capacity of border health facilities to reduce the burden placed upon them to provide services to the transnational population.

IMPACTS AND BENEFITS FROM TOURISM AN EXAMPLE FROM THAILAND

This qualitative research aims to study current impacts and agreement of benefits perceived from tourism in Chiang Saen District of Thailand. This is a case study that collected data by purposive sampling and used structured interview as a research tool. The in-depth interview was conducted with 26 interviewees who are involved in tourism and logistics. The findings illustrate the current impacts covering economic, sociocultural, and environment dimensions. The total impact demonstrates the most positive impact as income generation for investors, with environmental impact being harmful to the area. There are both agreements and disagreements of perceived benefits from tourism and logistics.

Key drivers of changes in the sediment loads of Chinese rivers discharging to the oceans

The magnitude and variation of the sediment loads transported by rivers have important implications for the functioning of river systems and changes in the sediment loads of rivers are driven by numerous factors. In this paper, the key drivers of changes in the sediment loads of the major rivers of China are identified by reviewing recent studies of changes in their sediment loads. Except for the Songhua River, which presents no clear tendency of change in runoff or sediment load, nearly all the major rivers of China are characterized by an apparent decline in annual sediment load. The total annual sediment load of major Chinese rivers transported to the coast decreased from 2.03 billion t/yr during the period 1955–1968 to 0.50 billion t/yr during the period 1997–2010. The primary drivers of changes in the sediment loads of the rivers are dam construction, implementation of soil and water conservation measures, catchment disturbance, agricultural practices, sand mining and climate change. Examples drawn from Chinese rivers are used to demonstrate the importance of these drivers. Construction of a large number of reservoirs in the Yangtze River basin represents the primary driver for the reduced sediment load of the Yangtze River. The implementation of soil and water conservation programmes is one of the key drivers for the sharp decline in the sediment load of the Yellow River. Catchment disturbance explains why the reduction of the sediment load of the Lancang-Mekong River at the Chiang Saen gauging station was much less than that at the Gajiu gauging station upstream. A reduction in sediment load resulting from the expansion of agricultural production may be the main driver for the reduced sediment load of the Huaihe River. The decrease in the sediment load of the Pearl River has been influenced by sand mining activities. Climate change is one of the key drivers responsible for the greatly reduced sediment load of the rivers in the Haihe River Basin.

Changes of Wiang Nong Lom and Nong Luang Wetlands in Chiang Saen Valley (Chiang Rai Province, Thailand) During the Period 1988–2017

Pressure on the Wiang Nong Lom and Nong Luang wetland resources in the Chiang Saen Valley of Chiang Rai Province (Thailand) has increased in recent years with the expansion of farmlands and other major sources of wetland conflict related to public land encroachment. Both of these wetlands have been designated as strategic ecosystems. Yet, there is a limited understanding of the way different wetlands respond to change drivers (agriculture, climate, population, etc.), and currently no scientifically valid protocols exist for local wetland mapping and monitoring. Distinguishing between small wetlands and land use and land cover (LULC) components is a challenging affair due to the highly heterogeneous landscape and spectral similarity of compositionally different types of tropical regions. The goals of this article are both technological and substantive, i.e., it aims to (A) propose a synthesis of quantitative techniques that can improve LULC mapping using remotely sensed data (Landsat TM, ETM+, OLI), and (B) assess the wetland changes during the last three decades and better understand the interaction between wetland changes, human population, and the environment. In regards to goal (A), the proposed classification approach employed a synthesis of techniques of decision tree classification (DTC), maximum likelihood classification (MLC), and Mahalanobis distance classification (MDC), with different bands and ancillary data inputs. The results demonstrated that the implementation of the DTC algorithms to address LULC mapping problems exhibited an overall mapping accuracy of 83.9%, which is significantly higher than that of MLC and MDC. It was found that the DTC technique performs well when combined with visible, near-infrared (NIR), and shortwave-infrared bands, a digital elevation model and normalized difference vegetation index layers. Subsequently, the postclassification analysis using DTC showed a notable improvement of approximately 88.0% classification accuracy. Regarding goal (B), our results showed that during the last 30 years, wetland areas in the Chiang Saen Valley have experienced a dramatic decrease of 30.5%, whereas forest landscape surrounding the wetlands has decreased by an astonishing 50.9%. Contrarily, we found that agricultural land size has increased by 24.3%. We suggest that ground data can be linked to the etiology of these results, including the gradual conversion of wetlands to rice cultivation fields as a result of the government rice pledging scheme. Large areas in the study region have been cultivated by para-rubber, palm oil, and pineapple agribusiness production since 2003. In addition, short-term subsidizing government policies promote intensive production for commercial agriculture prompting farmers to transition from subsistence to commercial farming, further impacting wetland conversion. As a result, and in further view of the fact that rapidly expanding agricultural areas have contributed significantly to the decrease of wetland areas during the last three decades, the Chiang Saen Valley wetlands have been designated as wetlands of international importance. The overall recommendation of the present work is that special land-use policy and relevant regulation and/or legislation are critical components of any effort to achieve wetland sustainability.

Seismic damage to ancient monuments in Chiang Saen (Northern Thailand): implication for historical earthquakes in Golden Triangle area

Over the last few decades, three moderate earthquakes (Mw greater than 6.0) occurred in and around the Golden Triangle area (including Myanmar, Thailand and Lao PDR) causing unprecedented damage and loss of lives in the epicentral region. In addition to the damage to modern structures, most heritage structures in Chiang Saen, a major city of the Lan Na kingdom (from the thirteenth to the eighteenth century), were also affected. This work is intended to present observed historical structure damage from recent earthquakes, which could provide evidence for the severity of historical earthquakes from the thirteenth to the eighteenth century. Based on historical records, geological evidence and observed damage to ancient monuments in this historic town, existing heritage stupas and temples constructed since the fourteenth century sustained only minor to moderate damage from these historical earthquakes. Considering the seismic vulnerability of these historical monuments, Chiang Saen might have never been subjected to severe ground shaking greater than MMI intensity VII, similar to the major earthquake in 460 A.D. along the Mae Chan fault, which was responsible for the large-scale liquefaction and inundation of ancient Yonok town. This information could be important for paleoseismological and historical earthquake research to constrain the recurrence interval of major active faults in this area. This article is part of the theme issue 'Environmental loading of heritage structures'.

Human-Induced Alterations to Land Use and Climate and Their Responses for Hydrology and Water Management in the Mekong River Basin

The Mekong River Basin (MRB) is one of the significant river basins in the world. For political and economic reasons, it has remained mostly in its natural condition. However, with population increases and rapid industrial growth in the Mekong region, the river has recently become a hotbed of hydropower development projects. This study evaluated these changing hydrological conditions, primarily driven by climate as well as land use and land cover change between 1992 and 2015 and into the future. A 3% increase in croplands and a 1–2% decrease in grasslands, shrublands, and forests was evident in the basin. Similarly, an increase in temperature of 1–6 °C and in precipitation of 15% was projected for 2015–2099. These natural and climate-induced changes were incorporated into two hydrological models to evaluate impacts on water budget components, particularly streamflow. Wet season flows increased by up to 10%; no significant change in dry season flows under natural conditions was evident. Anomaly in streamflows due to climate change was present in the Chiang Saen and Luang Prabang, and the remaining flow stations showed up to a 5% increase. A coefficient of variation &lt;1 suggested no major difference in flows between the pre- and post-development of hydropower projects. The results suggested an increasing trend in streamflow without the effect of dams, while the inclusion of a few major dams resulted in decreased river streamflow of 6% to 15% possibly due to irrigation diversions and climate change. However, these estimates fall within the range of uncertainties in natural climate variability and hydrological parameter estimations. This study offers insights into the relationship between biophysical and anthropogenic factors and highlights that management of the Mekong River is critical to optimally manage increased wet season flows and decreased dry season flows and handle irrigation diversions to meet the demand for food and energy production.