Variations in water resources in the Vietnamese Mekong Delta in response to climate change and their impacts on rice production

Abstract

A numerical hydraulic model was developed and used to investigate the spread of salinity intrusion and the propagation of flooding in the Vietnamese Mekong Delta under two proposed scenarios: "baseline" (2000s) and "future" (2090s). The baseline scenario was based on observed hydrological and salinity intrusion data from 1998 to 2006. The changes in upstream flow discharge in the future scenario (increased for most of the year) were derived from previous research results obtained using the Japan Meteorological Agency atmospheric general circulation model output for the IPCC SRES A1B scenario. The sea level rise in the A1B scenario (a projected 53-cm increase) was also included in the future scenario. The resulting salinity intrusion and flood water levels were then used to roughly estimate possible rice cropping durations. We found that large adverse changes in duration of rice cultivation in the future scenario were caused mainly by floods with greater peaks, larger areal extents, and longer durations. The area potentially suitable for growing triple rice crops decreased from 31 of the total delta area currently to 5 , whereas that potentially suitable for a single rice crop increased from 21 currently to 62 . Using GIS techniques, we divided the delta into three areas with different levels of rice vulnerability levels. Areas of high and medium vulnerability covered approximately 31 and 36 of the total delta area, respectively

Assessment of the impacts of climate change and brackish irrigation water on rice productivity and evaluation of adaptation measures in Ca Mau province, Vietnam

“…The assumed salt concentration in irrigation water used for this study is presented in Table 4. The assumption was done based on the projections by Khang et al (2008) and Le (2012) where modeling exercise reflects increased salinity in the groundwater. The present status for the representing sites was averaged out from monthly observations done for ten sites of Ca Mau city.…”

“…In addition, sensitivity analysis of the parameters associated to salinity was also done to evaluate the most sensitive parameters of the model. Simulations were also carried out for rice yield under both climate scenarios for the SA season by providing the necessary irrigation water at different concentration levels of salinity based on modeling projections by Khang et al (2008) and Le (2012) for all six GCMs. Furthermore, evaluation of agro-adaptation measures, namely altering the rice transplanting date and fertilizer application rate, was also done for both scenarios and seasons to counteract the negative impacts of climate change (Fig.…”

“…In addition to the direct implications of climate change on rice productivity, the production in many parts of the world is also affected by the indirect impacts of climate change particularly floods and droughts. Modeling studies in the Mekong Delta region in Vietnam illustrate single and multiple cropping patterns will be significantly reduced in the future due the intense and frequent floods (Khang et al 2008). Global-scale studies have validated rice productivity is increasing moderately and rapidly in the Southeast Asian region (Ray et al 2012); however, local-scale climate change impact assessment studies reflect potential yield is expected to decline under future climate for the same regions, and therefore, it is of major concern (Babel et al 2011;Masutomi et al 2009;Krishnan et al 2007).…”

Analysis and attribution of trends in water levels in the Vietnamese Mekong Delta

“…() and Khang et al . (, ) assessed the spread of saltwater intrusion and the extent of flooding in the VMD based on future scenarios using a hydraulic model. Manh et al .…”