Hydrological roles of the Cambodian floodplain of the Mekong River

Fujii, Hideto; Garsdal, Henrik; Ward, Peter; Ishii, Mikita; Morishita, Kanehiro; Boivin, Thomas G.

doi:10.1080/15715124.2003.9635211

Cited by 75 publications

(67 citation statements)

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“…Typical single-thread Mekong discharge upstream of the delta at Kratie, Cambodia ranges seasonally from 2000 to 40,000 m 3 s 21 (Figure 2). On the Song Hau, discharge magnitude is reduced by branching upstream, and seasonal variation is diminished by the influence of Tonle Sap lake, which acts as a natural flow capacitor that moderates flow within the delta [Fujii et al, 2003;Mekong River Commission, 2009]. Typical Song Hau discharge ranges seasonally from 5000 to 12,000 m 3 s 21 at Can Tho, Vietnam, 35 km upstream of the landward extent of our study area (Figure 1).…”

Section: Study Regionmentioning

confidence: 99%

“…That study took place in November, when Song Hau discharge is on average about 10% higher than during our study period, suggesting that, despite extensive dam construction in the interim [Xue et al, 2011], the high-flow salinity intrusion length has not changed dramatically in the past 20 years. The stability of the salinity intrusion length may be related in part to the [Fujii et al, 2003;Mekong River Commission, 2009], together with the importance of lowland precipitation (i.e., below significant damming) to water discharge in the Mekong delta. During the greater ebb, salinity was pushed 13 km downstream of section A, about 3 km landward of river km 0 (Figure 1), again based on integration of the velocity field at section A.…”

Section: Velocity Patternsmentioning

confidence: 99%

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Sediment dynamics in the lowerMekongRiver: Transition from tidal river to estuary

et al. 2015

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A better understanding of flow and sediment dynamics in the lowermost portions of large‐tropical rivers is essential to constraining estimates of worldwide sediment delivery to the ocean. Flow velocity, salinity, and suspended‐sediment concentration were measured for 25 h at three cross sections in the tidal Song Hau distributary of the Mekong River, Vietnam. Two campaigns took place during comparatively high‐seasonal and low‐seasonal discharge, and estuarine conditions varied dramatically between them. The system transitioned from a tidal river with ephemeral presence of a salt wedge during high flow to a partially mixed estuary during low flow. The changing freshwater input, sediment sources, and estuarine characteristics resulted in seaward sediment export during high flow and landward import during low flow. The Dinh An channel of the Song Hau distributary exported sediment to the coast at a rate of about 1 t s−1 during high flow and imported sediment in a spatially varying manner at approximately 0.3 t s−1 during low flow. Scaling these values results in a yearly Mekong sediment discharge estimate about 65% smaller than a generally accepted estimate of 110 Mt yr−1, although the limited temporal and spatial nature of this study implies a relatively high degree of uncertainty for the new estimate. Fluvial advection of sediment was primarily responsible for the high‐flow sediment export. Exchange‐flow and tidal processes, including local resuspension, were principally responsible for the low‐flow import. The resulting bed‐sediment grain size was coarser and more variable during high flow and finer during low, and the residual flow patterns support the maintenance of mid‐channel islands.

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Section: Study Regionmentioning

confidence: 99%

Section: Velocity Patternsmentioning

confidence: 99%

Sediment dynamics in the lowerMekongRiver: Transition from tidal river to estuary

et al. 2015

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“…Fujii et al [26] used RADARSAT data ranging from 1999 to 2003 to extract the inundated area and estimate the water quantity of Tonle Sap Lake. Using a WFFI method (Wavelet-based Filter for detecting spatio-temporal changes in Flood Inundation), Sakamoto et al assessed temporal changes in the extent of the inundated region in Cambodia and the Mekong Delta on the basis of MOD09 data from 2000 to 2004 [13].…”

Section: Introductionmentioning

confidence: 99%

Changes in the Lake Area of Tonle Sap: Possible Linkage to Runoff Alterations in the Lancang River?

Luo

et al. 2018

Remote Sensing

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Tonle Sap Lake is the largest freshwater lake in Southeast Asia. Water development infrastructures are increasingly being constructed in the Lancang-Mekong River Basin, which is a major concern considering its potential impact on Tonle Sap Lake. This study aimed to investigate variations in the area of the lake and discuss their possible linkage to runoff alterations in the Lancang River (Upper Mekong) by comparing runoff at the Yunjinghong hydrological station before and after significant changes in runoff trends that occurred in 2008. First, four commonly used water body extraction methods (MNDWI, NDWI, NDVI, and EVI) were compared and MNDWI was found to provide a better and more stable performance. Based on MOD09A1 data, MNDWI was used to extract the water area of the lake from 2000 to 2014, and characteristics of variations in the area before and after 2008 were analyzed. The water area of Tonle Sap Lake displayed an overall decreasing trend, and specifically decreased by 8.3% during the flood season and by 1.5% on average during the dry season after 2008. Seasonal variations in the water area of Tonle Sap Lake were dominantly influenced by runoff from the Mekong River. Compared with the period 2000-2007, runoff at Yunjinghong station were increased during the dry season (20.74%) and decreased during the flood season (34.25%) between 2008 and 2014. Changes in upstream runoff contributed to runoff at the Stung Treng station in the lower Mekong River by 6.17% (dry season) and −2.41% (flood season). Evidently, the operation of dams in the Lancang River does not primarily account for the area decrease of Tonle Sap Lake during the flood season. In contrast, runoff increase during the dry season mitigates the area decrease of Tonle Sap Lake to a certain extent.

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“…Since 1981, drastic water management alterations have been undertaken in the Vietnamese Mekong Delta to improve rice production (Duong and Cho 1994;Xuan and Matsui 1998;Hashimoto 2001;Minh and Kawaguchi 2002). Accompanied by the introduction of non-photoperiodsensitive high-yield rice varieties, infrastructure development for water resource management (e.g., the large-scale establishment of canals, irrigation/drainage systems and water sluices) has enabled rural farmers to cultivate rice two or three times annually (Kono 2001;Fujii et al 2003;Cho 2005).…”

Section: Introductionmentioning

confidence: 99%

Greenhouse gas emissions from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the Mekong Delta

Arai

Hosen

Hong

et al. 2015

Soil Science and Plant Nutrition

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The Mekong Delta produces 21 Mt of rough rice (Oryza sativa L.) and an estimated 24 Mt of straw (dry weight) annually. Approximately one fourth of the straw is burned on the field, which is a common practice in intensive rice cultivation systems in this region because there is limited time to prepare the field for the next crop. The spread of intensive rice production in the Delta may increase the total biomass of burning crop residues, significantly impacting greenhouse gas (GHG) emissions in Vietnam. In this study, GHG emissions from the major uses of straw (burning and mushroom beds) were monitored in a triple rice cropping system located in the central Mekong Delta. Between September 2011 and November 2012, both wind tunnel and closed chamber methods were used to measure the emissions of major GHGs from straw-burning and straw-mushroom cultivation systems, respectively. The global warming potential (GWP) was then determined. Methane (CH 4 ) and non-methane volatile organic carbon emissions (NMVOC) increased with lower modified combustion efficiency [MCE: emissions ratio of Carbon composing carbon dioxide (CO 2 -C) and carbon monooxide (CO-C) (CO 2 -C/(CO-C + CO 2 -C))]. Furthermore, higher moisture straw stacks generated lower nitrous oxide (N 2 O) emissions. Small straw stacks (5 or 10 kg dry straw) with higher moisture content emitted more carbon monoxide (CO), CH 4 and NMVOC. These results suggest that factors that increase the straw moisture content, such as rainfall, can cause smoldering combustion in small straw stacks or when straw is scattered on the ground, thereby inhibiting N 2 O emissions but enhancing CO, CH 4 and NMVOC. The measured N 2 O emissions contributed negligible amounts to the GWP compared with measured CO and CH 4 , which are relatively intense GHG emissions; this was likely a result of the slow and inefficient burning that was observed from the smaller straw stacks with higher moisture content. In this study, rice straw burning threatened to generate more GHGs than straw-mushroom (Volvariella volvacea (Bul. ex Fr.) Singer) cultivation under the studied agroecosystems.

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Hydrological roles of the Cambodian floodplain of the Mekong River

Cited by 75 publications

References 0 publications

Sediment dynamics in the lowerMekongRiver: Transition from tidal river to estuary

Sediment dynamics in the lowerMekongRiver: Transition from tidal river to estuary

Changes in the Lake Area of Tonle Sap: Possible Linkage to Runoff Alterations in the Lancang River?

Greenhouse gas emissions from rice straw burning and straw-mushroom cultivation in a triple rice cropping system in the Mekong Delta

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