Home About us Contact
|
Home About us Contact | ||
|
|
||
Mekong River Basin (mekong + river_basin)
Selected AbstractsStudies on the Mekong River Basin,Modelling of Hydrology and Water ResourcesHYDROLOGICAL PROCESSES, Issue 9 2008Kuniyoshi Takeuchi Principal Investigator of RR2002(6) Project No abstract is available for this article. [source] Seasonal changes in radiation and evaporation implied from the diurnal distribution of rainfall in the Lower MekongHYDROLOGICAL PROCESSES, Issue 9 2008Kumiko Tsujimoto Abstract Solar radiation is an important input to many empirical equations for estimating evaporation, which in turn plays an important role in the hydrologic cycle in the Lower Mekong River Basin due to the high evaporation potential of the tropical monsoon climate. Few proper meteorological data exist for the Lower Mekong River Basin, however, and the region's meteorological conditions, including seasonal variation in radiation and evaporation, have not been clarified. In this study, ground-based hourly hydrometeorological data were collected at three observation stations located in different land-use types (urban district, paddy area, and lake) in the Lower Mekong River Basin. These data were analysed to investigate the seasonal variation in radiation and evaporation related to the diurnal distribution of rainfall. Contrary to common expectations, our results showed that rainy and dry seasons had nearly the same amount of solar radiation in the Lower Mekong River Basin because (1) rainy seasons had a relatively larger amount of extraterrestrial radiation; (2) no rain fell on nearly half of the days during rainy seasons; and (3) the amount of solar radiation on rainy days reached 88% of that on non-rainy days. The third factor was attributed to the high frequency of evening rainfall. Furthermore, this rainfall,radiation relationship meant that rainy seasons had a large amount of net radiation due to the low reduction ratio of solar radiation and an increase in long-wave incoming radiation. Accordingly, rainy seasons had a high evaporation potential. Moreover, for the rain-fed rice paddies that prevail in this region, sufficient radiation during the rainy season would be a great advantage for rice growing. Copyright © 2008 John Wiley & Sons, Ltd. [source] Investigation of the Mekong River basin hydrology for 1980,2000 using the YHyMHYDROLOGICAL PROCESSES, Issue 9 2008Hapu Arachchige Prasantha Hapuarachchi Abstract This study investigates the Mekong River basin hydrology for the 1980,2000 period using a grid-based distributed hydrological model called Yamanashi Hydrological Model (YHyM). The performance of the model is evaluated using data observed at different locations and the results justify the physical soundness of the model. The seasonal variations of climatic and hydrological characteristics of the basin such as soil moisture, ground water saturation deficit, runoff, precipitation, evapotranspiration, etc. are analysed. On the basis of the simulated results, it is noticeable that there is no significant trend in the precipitation, discharge, or soil moisture state of the basin during the simulated period, though there are some seasonal variations which seem to be natural. However the analysis on the precipitation elasticity (E) of the river flow shows that the E values for all sub-basins are greater than unity, which indicates that x% change in annual precipitation can cause > x% change in annual river flow. Further the basin hydrological responses are analysed for a long term synthetically-induced drought the results of which show the significance of the base flow of the Mekong River basin. Copyright © 2008 John Wiley & Sons, Ltd. [source] Future hydroclimatology of the Mekong River basin simulated using the high-resolution Japan Meteorological Agency (JMA) AGCMHYDROLOGICAL PROCESSES, Issue 9 2008Anthony S. Kiem Abstract Analysis of future Japan Meteorological Agency atmospheric general circulation model (JMA AGCM) based climate scenarios for the Mekong River basin (MRB) indicates that annual mean precipitation will increase in the 21st century (2080,2099) by 4·2% averaged across the basin, with the majority of this increase occurring over the northern MRB (i.e. China). Annual mean temperatures are also projected to increase by approximately 2·6 °C (averaged across the MRB). As expected, these changes also lead to significant changes in the hydrology of the MRB. All MRB subbasins will experience an increase in the number of wet days in the ,future' and, importantly for sustainable water resources management and the mitigation of extreme events (e.g. floods and droughts), the magnitude and frequency of what are now considered extreme events are also expected to increase resulting in increased risk of flooding, but a reduction in the likelihood of droughts/low-flow periods,assuming water extraction is kept at a sustainable level. Despite the fact that the climate change impact projections are associated with significant uncertainty, it is important to act now and put in place policies, infrastructure and mitigation strategies to protect against the increased flooding that could occur. In addition, despite this study indicating a decrease in the number of ,low-flow' days, across most of the MRB, further analysis is needed to determine whether the reduction in low-flow days is enough to compensate for (and sustain) the rapidly increasing population and development in the MRB. Copyright © 2008 John Wiley & Sons, Ltd. [source] Estimating the evolution of vegetation cover and its hydrological impact in the Mekong River basin in the 21st centuryHYDROLOGICAL PROCESSES, Issue 9 2008Hiroshi Ishidaira Abstract The terrestrial biosphere plays a key role in regional energy and water cycles. Thus, for long-term hydrological predictions, possible future changes in vegetation cover must be understood. This study examined the evolution of vegetation cover in the 21st century and its estimated impact on river discharge in the Mekong River basin. Based on climatic predictions (TYN SC 2·03) under the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) A1FI, A2, B1, and B2, changes in vegetation type and the leaf area index (LAI) were simulated using a Lund-Potsdam-Jena-Dynamic Global Vegetation Model (LPJ-DGVM) and Terrestrial Biogeochemical Cycle Model (BIOME-BGC). The estimated LAI was then used in the rainfall-runoff analysis in the Yamanashi Distributed Hydrological Model (YHyM). The simulation results indicated a significant change in vegetation type mainly on the Tibetan Plateau and in mountainous areas, with the degree of change differing for each SRES scenario; LAI increases around the edge of the Tibetan Plateau and decreases in the lower reaches of the basin; and more conspicuous changes in river discharge in upstream areas than in the middle to lower reaches, mainly due to increases in precipitation in the plateau region. After the 2050s, the results suggested changes in river discharge will be slowed due to changes in evapotranspiration. Copyright © 2008 John Wiley & Sons, Ltd. [source] Building drought management capacity in the Mekong River basin,IRRIGATION AND DRAINAGE, Issue 3 2008Wilfried Hundertmark gestion de la sécheresse; développement des capacités; organisation de bassin; Mékong Abstract Over the past decades the Mekong River basin has experienced several droughts, the most recent of which occurred in the hydrological year 2004/2005. Impacts extended across agriculture, forestry, water resources, supply, industry, transport and the environment. In early 2006, the Mekong River Commission Secretariat initiated close consultations with the MRC member states Cambodia, Lao PDR, Thailand and Vietnam, aiming at the formulation of a common Drought Management Programme, which would enhance the existing drought management capacity and ensure effective support. This paper draws attention to the programme formulation process. It shows how national capacity needs were assessed and synthesized into a basin-wide capacity development programme. The paper concludes that in the context of international waters enhancing cooperation and capacity in drought management requires a strategic framework as an overall guideline for programme formulation and implementation. It defines a common terminology, mechanisms and linkages to integrated water resources management plans. The programme's long-term success depends on the ability to sustain the interest of the national partner institutions. Ultimately, enhanced capacity in drought management must demonstrate its impact on the level of vulnerability of the population living under drought-prone conditions. Copyright © 2008 John Wiley & Sons, Ltd. Au cours des dernières décennies, le bassin du Mékong a connu plusieurs sécheresses, la plus récente ayant eu lieu dans l'année hydrologique 2004/2005. L'impact a concerné l'agriculture, la forêt, les ressources en eau, la distribution, l'industrie, les transports et l'environnement. Au début de 2006, le Secrétariat de la Commission du Mékong a entamé des consultations étroites avec les états membres, le Cambodge, la RDP du Laos, la Thaïlande et le Vietnam, visant à l'élaboration d'un programme commun de gestion de la sécheresse, qui permettrait de renforcer les capacités existantes de gestion de la sécheresse et d'assurer un soutien efficace. Cet article attire l'attention sur le processus de formulation des programmes. Il montre comment les besoins nationaux de formation ont été évalués et synthétisés dans un programme de développement des capacités pour l'ensemble du bassin. L'article conclut que, dans le contexte des eaux internationales, le renforcement de la coopération et des capacités dans la gestion de la sécheresse a besoin d'un cadre stratégique d'ensemble et d'un guide global pour la formulation des programmes et leur mise en ,uvre. Il définit une terminologie commune, les mécanismes et les liens avec les plans de gestion intégrée des ressources en eau. Le succès à long terme du programme dépend de la capacité à maintenir l'intérêt des institutions nationales partenaires. En fin de compte, le renforcement des capacités dans la gestion de la sécheresse doit démontrer son impact sur le niveau de vulnérabilité de la population vivant dans les régions soumises à la sécheresse. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||