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The crop simulation model Decision Support System for Agrotechnology Transfer (DSSAT) was applied over the Mekong River Delta (MRD), Southern Vietnam, to assess future (2020–2050) impacts of climate change on rice production. The DSSAT model was driven using observed station data and projected climate data derived through the dynamical downscaling of three global climate models (GCMs) using the Weather Research and Forecasting (WRF) model. The WRF model was simulated at a spatial resolution of 30 km over the study region, and the large-scale driving fields for future climates were taken from the Coupled Model Inter-Comparison Project Phase 3 (CMIP3) global models ECHAM5, CCSM3, and MIROC5 under the A2 emission scenario. Rice growth during two main seasons, namely, the winter-spring (winter) and summer-autumn (summer), were selected to quantify impacts under both irrigated and rain-fed rice cultivation. The results from this climate-crop study suggest that under rain-fed conditions, winter rice yield was likely to experience nearly 24% reduction while summer rice yield was projected to decrease by about 49%. Without irrigation, the annual rice yield was projected to decrease by about 36.5%, and under irrigated conditions, climate change is likely to reduce annual irrigated rice yields by about 1.78%. Winter rice yield was likely to decrease by 4.7% while summer rice yield was projected to marginally increase by about 0.68%. Increasing temperatures and seasonal variations of precipitation are likely to significantly reduce rice yields under rain-fed condition. In addition, (1) a decrease (increase) in the number of rainy days during the dry (wet) season and (2) positive effects of elevated CO2 for rain-fed rice growth under each of the three WRF model realizations would markedly influence rice yields. With Vietnam being one of the largest exporters of rice, these findings have serious implications for the local agricultural sector. This also serves an early warning for the policymakers and stakeholders for effective planning of not only crop production but also water resource management. The findings call for prudent diversification strategy planning by those countries which import rice. [ABSTRACT FROM AUTHOR]

Climate change is one of the most serious challenges facing mankind in the 21st century. Extreme climatic events are expected to be more frequent and severe leading to various natural disasters. Vietnam, with more than 70% of the population working in agriculture and having a high density of inhabitants on the coastal plains, is one among those countries heavily impacted by climate change. The aim of this paper is to present a methodology to assess the impacts of climate change on a flood prone area of a coastal river basin in the central region of Vietnam. The hydrological simulations are based on a validated deterministic hydrological model MIKE SHE, which integrates geology, soil, topography, river systems and climate variables. The present-day climate, over the period of 1991–2010, was reasonably simulated by the hydrological model. Future climate (2091–2100) information was obtained from a dynamical downscaling of the global climate models, CCSM3.0, MIROC-medres and ECHAM5 under A2 scenario, using the Regional Climate Model: Weather Research and Forecasting Model. The result indicates that with this area, the ensemble future river flow under scenario A2 might increase up to 200% during rainy season and reduce to roughly 7–30% during dry season. The study also analyzed the changes in the flood dynamics of the study region, the hydrological shift and the uncertainties of climate change simulation. This paper showcases an operational approach to integrate the results from the impacts of climate change to flood protection measures that would help in devising resilience strategies. [ABSTRACT FROM AUTHOR]

This study used a regional climate model, driven at a resolution of 30 km, to derive climate estimates that were used as input to a hydrological model to determine stream flow in a changing climate. This regional climate model output was derived using the Weather Research and Forecasting model, which was used to downscale the general circulation model ECHAM5 T63 under the A2 greenhouse gas emission scenario for the future. Two river basins, Dakbla and Poko, over the Sesan catchment of the Lower Mekong region were considered for runoff modeling. A 10-year climatology of the recent past, 1991-2000, was used as the baseline for the present-day climate, and another 10-year climate over the period 2091-2100 was chosen for the future time slice. The results from the simulation of future stream flow indicate that, over both Dakbla and Poko river basins, the stream flow is likely to increase, especially during the peak rainfall season. The Dakbla River Basin shows a substantial increase in stream flow when compared with the Poko River Basin. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]