Your search found 9 records
1 Bricquet, J. P.; Janeau, Jean L.; Boonsaner, A.; Luc, J. P.; Huon, S.; Boulais, C.; Lestrelin, Guillaume; Kurian, Mathew. 2004. Catchment approach to combating soil erosion in Thailand. In Annual report 2003. IWMI Southeast Asia Regional Office, Bangkok, Thailand. pp.125-151.
(Location: IWMI-HQ Call no: IWMI 631.4 G570 MAG Record No: H037208)
2 Phan, Ha Hai An; Orange, Didier; Huon, S.; Henry des Tureaux, Thierry; Pham Van Rinh; Tran, Thi My Linh; Podwojewski Pascal. 2007. Evolution des teneurs en carbone organique et azote dans les matieres en suspension des eaux de surface d’un petit bassin versant agricole sur pente dans le Nord Vietnam. In French. [Organic carbon and nitrogen contents in the suspended matters of surface waters within a small agricultural watershed on sloping lands in Northern Vietnam]. Gestion integree des eaux et des sols : ressources, amenagements et risques en milieux ruraux et urbains, Editions AUF et IRD, Hanoi, Actes des Premieres Journees Scientifiques Inter-Reseaux de l’AUF, Hanoi, 6-9 novembre 2007. 6p.
(Location: IWMI HQ Record No: H040805)
This study deals with the organic carbon concentration and nitrogen concentration inside the suspended particulate matter transported by the small rivers with a watershed area below 10 ha and totally enclosed on sloping lands. The scientific purpose is to determine if these two components of soil losses from erosion process on topsoil could be used as tracers for the organic matter to point out the surface water pathway during one peak flow. The fluctuations in POC content, in C/N rate and in ?13C isotopic rate are no linked with the vegetation species on the sloping land during the process of surface runoff until the runoff collect in the small stream. However their absolute values are characteristic of each kind of vegetation cover. Then our results allow assuming that the mix of chemical tracers such as pH, water conductivity, organic carbon and nitrogen content in sediment with the associate measurements of ?13C isotopic component can be used to analyze the surface water pathway within a small sloping watershed during one peak flow. The next step will be the calculation of hydrological components of the hydrogram in relationship with the water pathway by the mixed equation use applied to the ?13C isotopic component of the organic matter form the sediments and from their corresponding soils.
3 Huon, S.; Ribolzi, Olivier; Aubry, E.; Soulileuth, B.; Longchamp, M.; Angeli, N.; Sengtaheuanghoung, O. 2008. Iron and manganese concentration levels in watercress cultivated within the main stream of the Houay Pano catchment, northern Lao PDR. Lao Journal of Agriculture and Forestry, Special issue no.17:113-128.
Catchment areas ; Watercress ; Metals ; Sedimentary materials ; Swamps ; Environmental effects / Laos / Houay Pano catchment
(Location: IWMI HQ Call no: e-copy only Record No: H041772)
(0.46 MB)
4 Ribolzi, Olivier; Thiebaux, Jean-Pierre; Bourdon, Emmanuel; Briquet, J. P.; Chaplot, V.; Huon, S.; Marchand, P.; Mouche, E.; Pierret, Alain; Robain, H.; de Rouw, Anneke; Sengtahevanghoung, O.; Soulileuth, B.; Valentin, Christian. 2008. Effect of fallow regrowth on stream water yield in a headwater catchment under shifting cultivation in northern Lao PDR. Lao Journal of Agriculture and Forestry, Special issue no.17:52-71.
Water yield ; Runoff ; Water balance ; Shifting cultivation ; Stream flow ; Water uptake ; Groundwater depletion ; Land use ; Water table / Laos
(Location: IWMI HQ Call no: e-copy only Record No: H041774)
http://www.nafri.org.la/documents/newsletter/Journal/journal_17/section3.pdf
https://vlibrary.iwmi.org/pdf/H041774.pdf
https://vlibrary.iwmi.org/pdf/H041774.pdf
(0.53 MB)
5 Ribolzi, O.; Cuny, Juliette; Sengsoulichanh, Phonexay; Mousques, Claire; Soulileuth, Bounsamai; Pierret, Alain; Huon, S.; Sengtaheuanghoung, O. 2010. Land use and water quality along a Mekong tributary in northern Lao P.D.R. Environmental Management, 47(2):291-302. [doi: https://doi.org/10.1007/s00267-010-9593-0]
Land use ; Water quality ; Measurement ; Water pollution ; Rivers ; Highlands ; Wastewater ; Surveys / Laos / Mekong Basin tributary / Houay Xon Stream / Luang Prabang Province
(Location: IWMI HQ Call no: e-copy only Record No: H043454)
(0.65 MB)
Improving access to clean water has the potential to make a major contribution toward poverty reduction in rural communities of Lao P.D.R. This study focuses on stream water quality along a Mekong basin tributary, the Houay Xon that flows within a mountainous, mosaic land-use catchment of northern Lao P.D.R. To compare direct water quality measurements to the perception of water quality within the riparian population, our survey included interviews of villagers. Water quality was found to vary greatly depending on the location along the stream. Overall, it reflected the balance between the stream self-cleaning potential and human pressure on the riparian zone: (i) high bacteria and suspended load levels occurred where livestock are left to free-range within the riparian zone; (ii) very low oxygen content and high bacteriological contamination prevailed downstream from villages; (iii) high concentrations of bacteria were consistently observed along urbanized banks; (iv) low oxygen content were associated with the discharge of organic-rich wastewater from a small industrial plant; (v) very high suspended load and bacteria levels occurred during flood events due to soil erosion from steep cultivated hill slopes. Besides these human induced pollutions we also noted spontaneous enrichments in metals in wetland areas fed by dysoxic groundwater. These biophysical measurements were in agreement with the opinions expressed by the majority of the interviewees who reported poor and decreasing water quality in the Houay Xon catchment. Based on our survey, we propose recommendations to improve or maintain stream water quality in the uplands of northern Lao P.D.R.
6 Huon, S.; Evrard, O.; Gourdin, E.; Lefevre, I.; Bariac, T.; Reyss, J.-L.; des Tureaux, T. H.; Sengtaheuanghoung, O.; Ayrault, S.; Ribolzi, O. 2017. Suspended sediment source and propagation during monsoon events across nested sub-catchments with contrasted land uses in Laos. Journal of Hydrology: Regional Studies, 9:69-84. [doi: https://doi.org/10.1016/j.ejrh.2016.11.018]
Rivers ; Catchment areas ; Suspended sediments ; Organic matter content ; Fallout ; Radionuclides ; Nitrogen ; Particle size ; Electrical conductivity ; Stream flow ; Monsoon climate ; Rain ; Flooding ; Soil erosion ; Storm runoff ; Hydrological factors ; Land use / Lao People's Democratic Republic / Houay Xon Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H048044)
http://www.sciencedirect.com/science/article/pii/S221458181630204X/pdfft?md5=7e7b3f476faa5301eb5701c1798aa8d9&pid=1-s2.0-S221458181630204X-main.pdf
https://vlibrary.iwmi.org/pdf/H048044.pdf
https://vlibrary.iwmi.org/pdf/H048044.pdf
(4.55 MB) (4.55 MB)
Study region: Houay Xon catchment in northern Laos.
Study focus: Because agricultural headwater catchments of SE Asia are prone to erosion and deliver a significant proportion of the total suspended sediment supply to major rivers and floodplains, the potential sources of sediments and their dynamics were studied for two successive storm flow events in June 2013. Characterization of suspended sediment loads was carried out along a continuum of 7 monitoring stations, combining analyses of fallout radionuclides, particle borne organic matter and stream water properties.
New hydrological insights: Radionuclide activities showed that remobilization of soil particles deposited during the previous rainy season or supplied by riverbank erosion is the dominant process, although pulses of surface-soil derived sediments also propagate downstream. This interpretation is supported by suspended organic matter data that also fingerprints the mixing of surface soil vs. subsurface particles. The study moreover highlights the advantages and the drawbacks of combining fallout radionuclides, particle borne organic matter composition and stream water characteristics to discriminate and quantify sediment sources and dynamics in rural areas undergoing urban sprawl.
Study focus: Because agricultural headwater catchments of SE Asia are prone to erosion and deliver a significant proportion of the total suspended sediment supply to major rivers and floodplains, the potential sources of sediments and their dynamics were studied for two successive storm flow events in June 2013. Characterization of suspended sediment loads was carried out along a continuum of 7 monitoring stations, combining analyses of fallout radionuclides, particle borne organic matter and stream water properties.
New hydrological insights: Radionuclide activities showed that remobilization of soil particles deposited during the previous rainy season or supplied by riverbank erosion is the dominant process, although pulses of surface-soil derived sediments also propagate downstream. This interpretation is supported by suspended organic matter data that also fingerprints the mixing of surface soil vs. subsurface particles. The study moreover highlights the advantages and the drawbacks of combining fallout radionuclides, particle borne organic matter composition and stream water characteristics to discriminate and quantify sediment sources and dynamics in rural areas undergoing urban sprawl.
7 Ribolzi, O.; Evrard, O.; Huon, S.; de Rouw, A.; Silvera, N.; Latsachack, K. O.; Soulileuth, B.; Lefevre, I.; Pierret, A.; Lacombe, Guillaume; Sengtaheuanghoung, O.; Valentin, C. 2017. From shifting cultivation to teak plantation: effect on overland flow and sediment yield in a montane tropical catchment. Scientific Reports, 7:1-12. [doi: https://doi.org/10.1038/s41598-017-04385-2]
Teak ; Plantations ; Sediment ; Shifting cultivation ; Overland flow ; Erosion ; Slopes ; Land use ; Land management ; Flow discharge ; Vegetation ; Catchment areas ; Rainfall-runoff relationships ; Infiltration ; Soil sampling / Southeastern Asia
(Location: IWMI HQ Call no: e-copy only Record No: H048176)
(2.73 MB)
Soil erosion supplies large quantities of sediments to rivers of Southeastern Asia. It reduces soil fertility of agro-ecosystems located on hillslopes, and it degrades, downstream, water resource quality and leads to the siltation of reservoirs. An increase in the surface area covered with commercial perennial monocultures such as teak plantations is currently observed at the expanse of traditional slash-andburn cultivation systems in steep montane environments of these regions. The impacts of land-use change on the hydrological response and sediment yields have been investigated in a representative catchment of Laos monitored for 13 years. After the gradual conversion of rice-based shifting cultivation to teak plantation-based systems, overland flow contribution to stream flow increased from 16 to 31% and sediment yield raised from 98 to 609 Mg km-2. This result is explained by the higher kinetic energy of raindrops falling from the canopy, the virtual absence of understorey vegetation cover to dissipate drop energy and the formation of an impermeable surface crust accelerating the formation and concentration of overland flow. The 25-to-50% lower 137Cs activities measured in soils collected under mature teak plantations compared to soils under other land uses illustrate the severity of soil erosion processes occurring in teak plantations.
8 Evrard, O.; Ribolzi, O.; Huon, S.; de Rouw. A.; Silvera, N.; Latsachack, K. O.; Soulileuth, B.; Lefevre, I.; Lacombe, Guillaume; Sengtaheuanghoung, O.; Valentin, C. 2017. Conversion of traditional cropland into teak plantations strongly increased soil erosion in montane catchments of Southeastern Asia [Abstract only] Paper presented at the American Geophysical Union Fall Meeting (AGU), New Orleans, USA, 11-15 December 2017. 1p.
Erosion ; Sediment ; Land use ; Farmland ; Teak ; Plantations ; Catchment areas ; Stream flow ; Vegetation ; Local communities ; Agroforestry / Southeast Asia / Lao People's Democratic Republic
(Location: IWMI HQ Call no: e-copy only Record No: H048619)
Soil erosion delivers an excessive quantity of sediment to rivers of Southeastern Asia. Land use is rapidly changing in this region of the world, and these modifications may further accelerate soil erosion in this area. Although the conversion of forests into cropland has often been investigated, much fewer studies have addressed the replacement of traditional slash-and-burn cultivation systems with commercial perennial monocultures such as teak plantations. The current research investigated the impact of this land use change on the hydrological response and the sediment yields from a representative catchment of Northern Laos (Houay Pano, 0.6 km²) where longterm monitoring (2002-2014) was conducted (http://msec.obs-mip.fr/). The results showed a significant growth in the overland flow contribution to stream flow (from 16 to 31%). Furthermore, sediment yields strongly increased from 98 to 609 Mg km-2. These changes illustrate the severity of soil erosion processes occurring under teak plantations characterized by the virtual absence of understorey vegetation to dissipate raindrop energy, which facilitates the formation of an impermeable surface crust. This counter-intuitive increase of soil erosion generated by afforestation reflects the difficulty to find sustainable production solutions for the local populations of Southeastern Asia. To reduce soil loss under teak plantations, the development of extensive agro-forestry practices could be promoted.
9 Ribolzi, O.; Lacombe, Guillaume; Pierret, A.; Robain, H.; Sounyafong, P.; de Rouw, A.; Soulileuth, B.; Mouche, E.; Huon, S.; Silvera, N.; Latxachak, K. O.; Sengtaheuanghoung, O.; Valentin, C. 2018. Interacting land use and soil surface dynamics control groundwater outflow in a montane catchment of the lower Mekong basin. Agriculture, Ecosystems and Environment, 268: 90-102. [doi: https://doi.org/10.1016/j.agee.2018.09.005]
Hydrology ; Land use ; Soil surface properties ; Soil crusts ; Groundwater recharge ; Flow discharge ; Water level ; Water table ; Catchment areas ; Stream flow ; Models ; Evapotranspiration ; Rain ; Runoff ; Infiltration ; River basins / China / Myanmar / Lao People's Democratic Republic / Thailand / Cambodia / Vietnam / Lower Mekong Basin
(Location: IWMI HQ Call no: e-copy only Record No: H048984)
Groundwater contribution to streamflow sustains biodiversity and enhances ecosystem services, especially under monsoon-driven climate where stream baseflow is often the only available water resource during the dry season. We assessed how land use change influences streamflow and its groundwater contribution in a small headwater catchment subject to shifting cultivation in Montane Southeast Asia. Continuous time series of rainfall, reference evapotranspiration, groundwater level, stream discharge and electrical conductivity (EC) of surface and groundwater were monitored from 2002 to 2007. With the rainfall-runoff model GR4J, we investigated temporal changes in the hydrological behaviour of the study catchment to verify consistencies with observed land use change. An EC-based hydrograph separation method allowed estimating the groundwater contribution to 104 stormflow events. Mean soil surface crusting rates corresponding to each of the nine land uses identified in the catchment were determined using 236 standard 1-m2 micro-plots. Mean plant cover for each land use was assessed in 10 × 10-m2 plots. Bedrock topography and soil layers’ structure were assessed by electrical resistivity tomography to determine pathways of subsurface storm flows. Our results indicate that an increase in the catchment's areal percentage of fallow from 33% to 71% led to a decrease in the annual runoff coefficient from 43% to 26%. The concurrent reduction of soil crusting rate over the catchment, from 48% to 30%, increased rainwater infiltration. Consecutively, groundwater contribution to storm streamflow increased from 83% to 94%, highlighting the protective role of a dense vegetation cover against flash floods. The overall reduction of the annual basin water yield for inter-storm streamflow from 450 to 185 mm suggests that the potential gain in groundwater recharge was offset by the increased root water uptake for evapotranspiration, as confirmed by the drop in the groundwater level. This analysis illustrates how two different land uses with opposite impacts on soil permeability (i/ extensive soil surface crusting under annual crops resulting in limited runoff infiltration or ii/ fallow regrowth promoting both infiltration and evapotranspiration) both inhibit groundwater recharge. The maintenance of strips of fallow buffers between annual crop plots can slow down runoff and locally promote infiltration and groundwater recharge while limiting evapotranspiration.
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