Your search found 13 records
1 Phommassack, T.; Chanthavongsa, A.; Sihavong, C.; Thonglatsamy, S.; Chanphengsay, A. 2001. Management of Soil Erosion Consortium (MSEC): An innovative approach for sustainable land management in Laos. In Maglinao, A. R.; Leslie, R. N. (Eds.), Soil erosion management research in Asian catchments: Methodological approaches and initial results - Proceedings of the 5th Management of Soil Erosion Consortium (MSEC) Assembly, held at Semarang, Central Java, Indonesia, 7-11 November 2000. Bangkok, Thailand: IWMI. Southeast Asia Regional Office. pp.153-170.
Erosion ; Surface runoff ; Catchment areas ; Geology ; Topography ; Climate ; Rain ; Water resources ; Land use ; Data collection ; Farming systems ; Population ; Settlement ; Land tenure ; Cropping systems ; Crop yield ; Livestock ; Public policy ; Soil management ; Land management ; Sustainability ; Institutions ; Organizations / Laos / Luang Prabang Province / Houay Pano Catchment
(Location: IWMI-HQ Call no: IWMI 631.45 G570 MAG Record No: H029254)
2 Vigiak, Olga; Ribolzi, O.; Pierret, A.; Sengtaheuanghoung, O.; Valentin, Christian. 2008. Trapping efficiencies of cultivated and natural riparian vegetation of northern Laos. Journal of Environmental Quality, 37: 889–897.
Riparian vegetation ; Sedimentation ; Rivers ; Runoff ; Control methods ; Sloping land ; Cultivation ; Rice ; Vegetables ; Teak ; Bananas ; Bamboos / Laos / Houay Pano Catchment
(Location: IWMI HQ Call no: IWMI 631.7.5 G708 VIG Record No: H040503)
In northern Laos, intensification of cultivation on sloping land leads to accelerated erosion processes. Management of riparian land may counteract the negative impacts of higher sediment delivery rates on water quality. This study assessed water and sediment concentration trapping efficiencies of riparian vegetation in northern Laos and the effect of cultivation of riparian land on water quality. Runoff flowing in and out of selected riparian sites was monitored by means of open troughs. In 2005, two native grass, two bamboo, and two banana sites were monitored. In 2006, adjacent to steep banana, bamboo, and native grass sites, three upland rice sites were established and monitored. Water trapping efficiency (WTE) and sediment concentration trapping efficiency (SCTE) were calculated on an event basis; means and 95% confi dence intervals (CIs) were estimated with a bootstrapping approach. Confidence intervals were large and overlapping among sites. Seepage conditions severely limited trapping efficiency. Native grass resulted in the highest WTE (95% CI, -0.10 to 0.23), which was not significantly different from zero. Banana resulted in the highest SCTE (95% CI, 0.06–0.40). Bamboo had negative WTE and SCTE. Median outflow runoff from rice sites was nine times the inflow. Median outflow sediment concentration from rice sites was two to five times that of their adjacent sites and two to five times the inflow sediment concentration. Although lowtillage banana plantation may reduce sediment concentration of runoff, cultivation of annual crops in riparian land leads to delivery of turbid runoff into the stream, thus severely affecting stream water quality.
3 Sengtaheuanghoung, O.; Valentin, Christian; Ribolzi, Olivier; de Rouw, Anneke; Thiebaux, Jean-Pierre. 2007. The impact of rapid land use changes upon sediment yields from agricultural catchments in northern Lao PDR. Actes des JSIRAUF, Hanoi, Vietnam, 6-9 novembre 2007. 5p.
Catchment areas ; Sedimentation ; Land use ; Cropping systems ; Shifting cultivation ; Rain ; Runoff / Laos / Houay Pano catchment
(Location: IWMI HQ Call no: IWMI 333.91 G708 SEN Record No: H040865)
To provide data that are lacking at the catchment scale, outflow and sediment yield have Been monitored from 8 small (0.5-64 ha) rural catchments since 2001 in northern Lao PDR. Soil conservation strategies have been developed and tested on three of these catchments. Results clearly show that sediment yields can be reduced from 5-11 Mg ha-1 yr-1 under the current slash and burn system to nearly nil when appropriate practices are selected. These include improved fallow systems based on legumes. These innovative practices rehabilitate degraded land and enhance water quality.
4 de Rouw, Anneke; Douillet, M.; Tjiantahosong, H.; Ribolzi, Olivier; Thiebaux, Jean-Pierre. 2007. Dispersal of weed seeds by erosion and flow processes in upland fields. In Gebbie, L.; Glendinning, A.; Lefroy-Braun, R.; Victor, M. (Eds.). Proceedings of the International Conference on Sustainable Sloping Lands and Watershed Management: Linking Research to Strengthen upland Policies and Practices, National Agriculture and Forestry Research Institute of Lao PDR (NAFRI), Vientiane, Lao PDR, 2007. Vientiane, LAO PDR: National Agriculture and Forestry Research Institute of Lao PDR (NAFRI) pp.156-166.
Erosion ; Seeds ; Weeds ; Grasses ; Rice ; Shifting cultivation ; Catchment areas / Laos / Houay Pano Catchment
(Location: IWMI HQ Call no: IWMI 333.91 708 ROW Record No: H041519)
http://www.nafri.org.la/documents/SSLWM/SSLWMpapers/chapter2/ch2_04_derouw.pdf
https://vlibrary.iwmi.org/pdf/H041519.pdf
https://vlibrary.iwmi.org/pdf/H041519.pdf
5 Dupin, B.; de Rouw, A.; Phantahvong, K. B.; Valentin, Christian. 2009. Assessment of tillage erosion rates on steep slopes in northern Laos. Soil and Tillage Research, 103(1):119-126. [doi: https://doi.org/10.1016/j.still.2008.10.005]
Tillage ; Erosion ; Shifting cultivation ; Upland rice ; Weed control ; Farming systems ; Sloping land ; Subsistence farming / Laos / Houay Pano Catchment / Luang Prabang District
(Location: IWMI HQ Call no: e-copy only Record No: H041849)
(0.58 MB)
In the hills of south-east Asia shifting cultivation is developing towards more permanent cropping systems. In association with short fallow periods, fields suffer from weed pressure and this, in turn, leads to more frequent and deeper manual tillage. Due to steep slopes these operations induce tillage erosion. Measurements of such soil losses under on-farm conditions are still scarce. In this study tillage erosion was assessed and a predictive model of tillage erosion was established based on slope angle and contact cover, i.e. basal crop area and weed cover. The experiments were conducted in the Houay Pano, Northern Laos. The farmers cultivate annual crops in rotation with 1–3 year fallow periods without external inputs and using only hand tools. Tillage erosion was assessed using the tracer method across nine slope classes (0.30–1.10 m m1) for two crops, upland rice and Job’s tears (Coix lacryma-jobi L.). Soil movement due to land preparation and weeding were assessed separately because different tools are used, a medium size hoe and a small curved hoe. A multivariate regression showed a highly significant relation (R2 = 0.83) between soil losses due to land preparation, slope gradient and contact cover. Predicting models of soil losses due to weeding were also highly significant (R2 = 0.79 for upland rice, R2 = 0.88 for Job’s tears), confirming the importance of tillage erosion on steep slopes (4, 6 and 11 t ha1 year1 on slopes with gradients of 0.30, 0.60 and 0.90 m m1, respectively). Tillage erosion has increased exponentially over the last 40 years because of weed invasion associated with short fallow periods; the initially no-till system has changed into a system heavily dependent on tillage to control weeds and this greatly contributes to soil degradation.
6 Bourdon, Emmanuel; Blavet, D.; Luankongkam, O.; Soulileuth, B.; Chanhphengxay, A.; Pierret, Alain; Ribolzi, Olivier. 2008. Semi-quantitative evaluation of waterlogging duration using two models based on soil colour in a representative upland catchment of northern Lao PDR. Lao Journal of Agriculture and Forestry, Special issue no.17:150-165.
Groundwater ; Waterlogging ; Soil properties ; Water table ; Catchment areas ; Models / Laos / Houay Pano catchment
(Location: IWMI HQ Call no: e-copy only Record No: H041771)
(0.57 MB)
Groundwater is a vital resource for rural populations in tropical areas who depend on seasonal rainfall. Groundwater is often the only source of water feeding streams, allowing them to flow throughout the dry season. The aim of this study was to evaluate two models for estimating the average duration that soil is waterlogged by shallow groundwater table. These models, based on variations in soil colour, were developed by Blavet et al (2000) from observations and measurements made in a semi-arid environment in West Africa. Therefore there is a need to evaluate whether these models are also pertinent in a mountainous context of northern Laos. Our approach consisted in comparing data obtained from field measurements (water table level, morpho-pedological features including soil colour) with predictions made by the models. This study was carried out along two transects with contrasting characteristics in terms of the landscape morphology as well as the soil hydrodynamic: the first was in an open swampy valley with convex hillslopes, the second was in a steep-banked and narrow valley with convexo-concave hillslopes. Preliminary results from our study identified relationships between soil colour and the mean rate of soil waterlogging and are a first step for developing an inexpensive and simple method to predict soil saturation in this environment.
7 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)
8 Vandervaere, J. P.; Ribolzi, Olivier; Valentin, Christian; Lapetite, J. M.; Miscioscia, J. M.; Sengtaheuanghoung, O. 2008. A new tension infiltrometer to measure the soil hydrodynamic properties on steep slopes. Lao Journal of Agriculture and Forestry, Special issue no.17:73-90.
(Location: IWMI HQ Call no: e-copy only Record No: H041778)
(0.61 MB)
9 Valentin, Christian; Sengtahevanghoung, O.; Ribolzi, Olivier; Pierret, Alain; Vigiak, Olga. 2008. The MSEC project in the Lao PDR: achievements, ongoing activities and perspectives on sustainable alternative farming practices for the uplands. Lao Journal of Agriculture and Forestry, Special issue no.17:2-30.
Land use ; Soil conservation ; Sloping land ; Erosion ; Shifting cultivation ; Farming systems / Laos / Houay Pano catchment
(Location: IWMI HQ Call no: e-copy only Record No: H041776)
http://www.nafri.org.la/documents/newsletter/Journal/journal_17/section1.pdf
https://vlibrary.iwmi.org/pdf/H041776.pdf
https://vlibrary.iwmi.org/pdf/H041776.pdf
(0.98 MB)
10 Robain, H.; Le Troquer, Yann; Sounyaphong, P.; Chiakoua, B. X.; Bourdon, Emmanuel; Ribolzi, Olivier. 2008. Assessment of soil organisation and monitoring of soil water content using electrical resistivity tomography in the uplands of Lao PDR. Lao Journal of Agriculture and Forestry, Special issue no.17:167-182.
Soil water content ; Electrical conductivity ; Monitoring ; Groundwater recharge ; Sloping land ; Infiltration ; Catchment areas / Laos / Houay Pano Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H041775)
http://www.nafri.org.la/documents/newsletter/Journal/journal_17/section9.pdf
https://vlibrary.iwmi.org/pdf/H041775.pdf
https://vlibrary.iwmi.org/pdf/H041775.pdf
(0.78 MB)
11 Mouche, E.; Moussu, F.; Mugler, C.; Ribolzi, O.; Valentin, C.; Sengtahevanghoung, O.; Lacombe, Guillaume. 2014. Impact of land-use change on the hydrology of North Lao PDR watersheds. In Daniell, T. M.; Van Lanen, H. A. J.; Demuth, S.; Laaha, G.; Servat, E.; Gil Mahe, J.-F. B.; Paturel, J.-E.; Dezetter, A.; Ruelland, D. (Eds.). Hydrology in a changing world : environmental and human dimensions: proceedings of the FRIEND [Flow Regime from International Experimental and Network Data] Water Conference, Montpellier, France, 7-10 October 2014. Wallingford, UK: International Association of Hydrological Sciences (IAHS). pp.84-89. (IAHS Publication 363)
Land use ; Hydrology ; Watersheds ; Impact assessment ; Agriculture ; Catchment areas ; Rain ; Runoff ; River basins / Lao People's Democratic Republic / Mekong River / Nam Khan Watershed / Nam Ou Watershed / Nam Suong Watershed / Nam Lik Watershed / Nam Ngum Watershed / Houay Pano Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H046864)
(0.42 MB)
We investigated the impact of land-use change on the hydrology of different major Lao tributary watersheds of Mekong River. The region is the North of Laos centred on Luang Prabang and the watersheds are the Nam Khan, Nam Ou, Nam Suong, Nam Lik and Nam Ngum. An additional small agricultural catchment called Houay Pano close to the Nam Khan, is also considered. We used the lumped rainfall–runoff conceptual models GR4J and GR2M, developed by Irstea in France, the Mekong River Commission hydro-meteorological database and the Japanese Aphrodite meteorological database. The objective was to detect in the hydrological regime of the watersheds an impact of de(re)forestation, processes known to have occurred since the 1980s, but at a degree which has not been quantified. For this purpose we adopted the cross simulation methodology developed by Irstea which has proved to be efficient to detect trends in long term watershed hydrology. The results did not show any significant hydrological change since 1960. On the other hand the application of the same methodology to the small catchment Houay Pano surveyed since 2001 proved to be convincing. We saw evidence of the impact of slash and burn practice, followed by a long fallow period, on a catchment’s hydrology over a seven year period.
12 Lacombe, Guillaume; Ribolzi, O.; de Rouw, A.; Pierret, A.; Latsachak, K.; Silvera, N.; Pham Dinh, R.; Orange, D.; Janeau, J.-L.; Soulileuth, B.; Robain, H.; Taccoen, A.; Sengphaathith, P.; Mouche, E.; Sengtaheuanghoung, O.; Tran Duc, T.; Valentin, C. 2015. Afforestation by natural regeneration or by tree planting: examples of opposite hydrological impacts evidenced by long-term field monitoring in the humid tropics. Hydrology and Earth System Sciences Discussions, 12:12615-12648. [doi: https://doi.org/10.5194/hessd-12-12615-2015]
Afforestation ; Plantations ; Tectona grandis ; Hydrological factors ; Humid tropics ; Ecosystem services ; Land use ; Soil conservation ; Water conservation ; Catchment areas ; Rain ; Runoff ; Models / Lao People s Democratic Republic / Vietnam / Houay Pano Catchment / Dong Cao Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H047340)
http://www.hydrol-earth-syst-sci-discuss.net/12/12615/2015/hessd-12-12615-2015.pdf
https://vlibrary.iwmi.org/pdf/H047340.pdf
https://vlibrary.iwmi.org/pdf/H047340.pdf
(3.39 MB) (3.39 MB)
The humid tropics are exposed to an unprecedented modernization of agriculture involving rapid and highly-mixed land-use changes with contrasted environmental impacts. Afforestation is often mentioned as an unambiguous solution for restoring ecosystem services and enhancing biodiversity. One consequence of afforestation is the alteration of streamflow variability controlling habitats, water resources and flood risks. We demonstrate that afforestation by tree planting or by natural forest regeneration can induce opposite hydrological changes. An observatory including long-term field measurements of fine-scale land-use mosaics and of hydro-meteorological variables has been operating in several headwater catchments in tropical Southeast Asia since 2001. The GR2M water balance model repeatedly calibrated over successive 1 year periods, and used in simulation mode with specific rainfall input, allowed the hydrological effect of land-use change to be isolated from that of rainfall variability in two of these catchments in Laos and Vietnam. Visual inspection of hydrographs, correlation analyses and trend detection tests allowed causality between land-use changes and changes in seasonal flows to be ascertained. In Laos, the combination of shifting cultivation system (alternation of rice and fallow) and the gradual increase of teak tree plantations replacing fallow, led to intricate flow patterns: pluri-annual flow cycles induced by the shifting system, on top of a gradual flow increase over years caused by the spread of the plantation. In Vietnam, the abandonment of continuously cropped areas mixed with patches of tree plantations led to the natural re-growth of forest communities followed by a gradual drop in streamflow. Soil infiltrability controlled by surface crusting is the predominant process explaining why two modes of afforestation (natural regeneration or planting) led to opposite changes in flow regime. Given that commercial tree plantations will continue to expand in the humid tropics, careful consideration is needed before attributing to them positive effects on water and soil conservation.
13 Lacombe, Guillaume; Ribolzi, O.; de Rouw, A.; Pierret, A.; Latsachak, K.; Silvera, N.; Dinh, R. P.; Orange, D.; Janeau, J.-L.; Soulileuth, B.; Robain, H.; Taccoen, A.; Sengphaathith, P.; Mouche, E.; Sengtaheuanghoung, O.; Tran Duc, T.; Valentin, C. 2016. Contradictory hydrological impacts of afforestation in the humid tropics evidenced by long-term field monitoring and simulation modelling. Hydrology and Earth System Sciences, 20:2691-2704.
Humid tropics ; Hydrological factors ; Afforestation ; Natural regeneration ; Plantations ; Monitoring ; Simulation models ; Land use ; Land cover change ; Ecosystem services ; Forest conservation ; Catchment areas ; Rainfall-runoff relationships ; Stream flow ; Cropping systems ; Water conservation ; Soil conservation ; Soil surface properties ; Tectona grandis / Lao People's Democratic Republic / Vietnam / Houay Pano Catchment / Dong Cao Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H047644)
http://www.hydrol-earth-syst-sci.net/20/2691/2016/hess-20-2691-2016.pdf
https://vlibrary.iwmi.org/pdf/H047644.pdf
https://vlibrary.iwmi.org/pdf/H047644.pdf
The humid tropics are exposed to an unprecedented modernisation of agriculture involving rapid and mixed land-use changes with contrasted environmental impacts. Afforestation is often mentioned as an unambiguous solution for restoring ecosystem services and enhancing biodiversity. One consequence of afforestation is the alteration of streamflow variability which controls habitats, water resources, and flood risks. We demonstrate that afforestation by tree planting or by natural forest regeneration can induce opposite hydrological changes. An observatory including long-term field measurements of fine-scale land-use mosaics and of hydrometeorological variables has been operating in several headwater catchments in tropical southeast Asia since 2000. The GR2M water balance model, repeatedly calibrated over successive 1-year periods and used in simulation mode with the same year of rainfall input, allowed the hydrological effect of land-use change to be isolated from that of rainfall variability in two of these catchments in Laos and Vietnam. Visual inspection of hydrographs, correlation analyses, and trend detection tests allowed causality between land-use changes and changes in seasonal streamflow to be ascertained. In Laos, the combination of shifting cultivation system (alternation of rice and fallow) and the gradual increase of teak tree plantations replacing fallow led to intricate streamflow patterns: pluri-annual streamflow cycles induced by the shifting system, on top of a gradual streamflow increase over years caused by the spread of the plantations. In Vietnam, the abandonment of continuously cropped areas combined with patches of mix-trees plantations led to the natural re-growth of forest communities followed by a gradual drop in streamflow. Soil infiltrability controlled by surface crusting is the predominant process explaining why two modes of afforestation (natural regeneration vs. planting) led to opposite changes in streamflow regime. Given that commercial tree plantations will continue to expand in the humid tropics, careful consideration is needed before attributing to them positive effects on water and soil conservation.
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