Characterization of water quality variation in the Mekong River at Vientiane by frequent observations

Iida, Toshiaki; Inkhamseng, Somphone; Yoshida, Koshi; Tanji, Hajime

doi:10.1002/hyp.8084

Cited by 13 publications

(10 citation statements)

References 48 publications

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“…For FWMCTN and FWMCTP, VolR was identified as one of the top three factors along with AvFlow and PkFlow, particularly for FWMCTP. The negative effect of VolR on FWMCTN and FWMCTP was likely due to the effects of dilution with an assumption of fixed rate of mobilization (Keller et al, 2008; Iida et al, 2011). Even though VolR was excluded for the PLS analysis for LTN and LTP, the importance of VolR on LTN and LTP should not be ignored.…”

Section: Discussionmentioning

confidence: 99%

“…Hydrologic and weather factors were also highly linked to the water chemistry in runoff and affected nutrient loss (Tisseuil et al, 2008; Townsend‐Small et al, 2011; Shrestha et al, 2012). Among factors affecting water quality, VolR was widely accepted by many researchers to be the main factor controlling N and P (Moog and Whiting, 2002; Turgeon and Courchesne, 2008; Salvano et al, 2009; Sui et al, 2010; Iida et al, 2011). Cockburn and Lamoureux (2008) reported that volume and intensity of snowmelt runoff were important controls on sediment yield and consequent P losses.…”

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confidence: 99%

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Critical Factors Affecting Field-Scale Losses of Nitrogen and Phosphorus in Spring Snowmelt Runoff in the Canadian Prairies

et al. 2013

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A long-term, field-scale study in southern Manitoba, Canada, was used to identify the critical factors controlling yearly transport of nitrogen (N) and phosphorus (P) by snowmelt runoff. Flow monitoring and water sampling for total and dissolved N and P were performed at the edge of field. The flow-weighted mean concentrations and loads of N and P for the early (the first half of yearly total volume of snowmelt runoff), late (the second half of yearly total volume of snowmelt runoff), and yearly snowmelt runoff were calculated as response variables. A data set of management practices, weather variables, and hydrologic variables was generated and used as predictor variables. Partial least squares regression analysis indicated that critical factors affecting the water chemistry of snowmelt runoff depended on the water quality variable and stage of runoff. Management practices within each year, such as nitrogen application rate, number of tillage passes, and residue burial ratio, were critical factors for flow-weighted mean concentration of N, but not for P concentration or nutrient loads. However, the most important factors controlling nutrient concentrations and loads were those related to the volume of runoff, including snow water equivalent, flow rate, and runoff duration. The critical factors identified for field-scale yearly snowmelt losses provide the basis for modeling of nutrient losses in southern Manitoba and potentially throughout areas with similar climate in the northern Great Plains region, and will aid in the design of effective practices to reduce agricultural nonpoint nutrient pollution in downstream waters.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Critical Factors Affecting Field-Scale Losses of Nitrogen and Phosphorus in Spring Snowmelt Runoff in the Canadian Prairies

et al. 2013

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“…The Mekong river basin is functionally divided into two parts: the Upper Mekong basin (UMB) and the Lower Mekong basin (LMB) [ 27 ]. The UMB, located in the temperate and high altitude semi-tropical zone of China (Lancang Jiang), is covered by alpine and mountainous areas with a low population density while the LMB, located in the tropical zone of South-East Asia, drains more than 76% (60 000 km 2 ) of the Mekong basin and is characterized by a low, flat topography with a high population density [ 20 ]. The LMB is well known for its rich freshwater biodiversity; particularly fish which provides a livelihood for million people [ 28 ].…”

Section: Methodsmentioning

confidence: 99%

“…Compared to Thailand, water quality monitoring in Laos, Cambodia and Vietnam is very limited and monitoring complicated, in particular the unclear definition of responsibilities and competences among different ministries and agencies at national and regional levels [ 16 – 19 ]. In Laos, recent studies into water quality have shown high concentrations of nutrients (NO 3 and P), nitrogenous matter and TSS at Vientiane city and in upstream Mekong located in northern of Laos [ 20 , 21 ]. In Cambodia, some concerns have been raised regarding the degradation of water quality in Tonle Sap lake and the 3S river system (Sesan, Sekong, Sraepork) [ 22 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

Evidence of Water Quality Degradation in Lower Mekong Basin Revealed by Self-Organizing Map

2016

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To reach a better understanding of the spatial variability of water quality in the Lower Mekong Basin (LMB), the Self-Organizing Map (SOM) was used to classify 117 monitoring sites and hotspots of pollution within the basin identified according to water quality indicators and US-EPA guidelines. Four different clusters were identified based on their similar physicochemical characteristics. The majority of sites in upper (Laos and Thailand) and middle part (Cambodia) of the basin were grouped in two clusters, considered as good quality water with high DO and low nutrient levels. The other two clusters were mostly composed of sites in Mekong delta (Vietnam) and few sites in upstream tributaries (i.e., northwestern Thailand, Tonle Sap Lake, and swamps close to Vientiane), known for moderate to poor quality of water and characterized by high nutrient and dissolved solid levels. Overall, we found that the water in the mainstream was less polluted than its tributaries; eutrophication and salinity could be key factors affecting water quality in LMB. Moreover, the seasonal variation of water quality seemed to be less marked than spatial variation occurring along the longitudinal gradient of Mekong River. Significant degradations were mainly associated with human disturbance and particularly apparent in sites distributed along the man-made canals in Vietnam delta where population growth and agricultural development are intensive.

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“…Lu and Siew, ). The former is characterized by alpine and mountainous areas with a low population density, while the latter is characterized by low, flat topography with a high population density (Iida et al , ). The river runs thus from cool temperate to tropical climates from its origin to the South China Sea.…”

Section: Study Areamentioning

confidence: 99%

Reappraisal of sediment dynamics in the Lower Mekong River, Cambodia

Kummu

Oeurng

2014

Earth Surf Processes Landf

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The Mekong Basin in southeast Asia is facing rapid development, impacting its hydrology and sediment dynamics. Although the understanding of the sediment transport rates in the Mekong is gradually growing, the sediment dynamics in the lower Mekong floodplains (downstream from Kratie) are poorly understood. The aim of this study is to conduct an analysis to increase the understanding of the sediment dynamics at the Chaktomuk confluence of the Mekong River, and the Tonle Sap River in the Lower Mekong River in Cambodia. This study is based on the data from a detailed field survey over the three hydrological years (May 2008-April 2011 at the two sites (the Mekong mainstream and the Tonle Sap River) at the Chaktomuk confluence. We further compared the sediment fluxes at Chaktomuk to an upstream station (i.e. Mukdahan) with longer time series. Inflow sediment load towards the lake was lower than that of the outflow, with a ratio on average of 84%. Although annually only a small amount of sediment load from the Tonle Sap contributes to the delta (less than 15%), its share is substantial during the February-April period. The annual sediment load transport from the confluence to the delta in 2009 and 2010 accounted for 54 and 50 Mt, respectively. This was on average only 55% of the sediment fluxes measured at Mukdahan, a more upstream station. Furthermore when compared to sediment loads further downstream at the Cambodia-Vietnam border, we found that the suspended sediment flux continued to decline towards the South China Sea. Our findings thus indicate that the sediment load to the South China Sea is much lower than the previous estimate 150-160 Mt/yr.

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Characterization of water quality variation in the Mekong River at Vientiane by frequent observations

Cited by 13 publications

References 48 publications

Critical Factors Affecting Field-Scale Losses of Nitrogen and Phosphorus in Spring Snowmelt Runoff in the Canadian Prairies

Critical Factors Affecting Field-Scale Losses of Nitrogen and Phosphorus in Spring Snowmelt Runoff in the Canadian Prairies

Evidence of Water Quality Degradation in Lower Mekong Basin Revealed by Self-Organizing Map

Reappraisal of sediment dynamics in the Lower Mekong River, Cambodia

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