Your search found 2 records
1 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.
2 Orange, Didier; Phan, Ha Hai An; Lequeux, Brice; Henry des Tureaux, Thierry; Pham, Van Rinh; Toan, T. D. 2007. Charges de fond et suspensions transportees par les eaux d’ecoulement dans un petit bassin versant agricole sur pentes dans le Nord 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; Paper presented at Conference, Integrated Management of Waters and Soils: resources, infrastructures and risks in rural and urban areas, Hanoi, Vietnam, 6-9 November 2007. 6p.
(Location: IWMI HQ Call no: 333.91 G784 ORA Record No: H040807)
A small agricultural watershed on sloping lands (around 50 ha) in Northern Vietnam is equipped with 5 runoff measurement stations named weir. Each weir is representative of one vegetation cover (forest, fodder, cassava and old fallow). There is no relationship between bed load and rainfall amount due to a threshold process, but it is directly linked to the vegetation cover. In 2006, bed load losses are quite much important on the cassava crop (879 kg/ha/yr) than at the other weirs: 131 kg/ha/yr for old fallow, 83 kg/ha/yr for pluriannual plantation and 52 kg/ha/yr for forest. From some event measurements, the mean suspended load during the rising peak was a range 0.4-2.9 g/l with a SM peak around 3 to 8 g/l; the suspended load during the base flow was around 10-20 mg/l. It is impossible to predict the SM load with the discharge. For each weir, the best correlation is between SM load and Rindex emphasizing the duration and the amount of the rain event. The calculation of suspended load confirms the soil loss by suspended load is much more important than by bed load, even if the 95% of suspended load occurs during the peak events. On the whole watershed, the erosion amount by suspended load is 1.2 t/ha for 0.6 t/ha for bed load. More trees are in the basin, less is the suspended load; and at the opposite, the agricultural practices increase the amount of suspended load.
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