Sensitivity of Salinity Intrusion to Sea Level Rise and River Flow Change in Vietnamese Mekong Delta-Impacts on Availability of Irrigation Water for Rice Cropping

Abstract

The combined impact of sea level rise and reduction of the Mekong River flow in the dry season on salinity intrusion and rice cropping in the Vietnamese Mekong Delta was assessed in this study. The MIKE11 model was used to simulate flow and salinity intrusion from December to June for the medium-term (mid-2030s) and long-term (mid-2090s) scenarios using data derived from the SRES B2 climate change projection. The sea level rise values for two scenarios were 20 cm and 45 cm, while the rates of change for the Mekong River flow were 15 and 29 , respectively. The results obtained for the mid-2030s and mid-2090s scenarios show that the 2.5 g/L saline front is likely to shift upstream by 10 km and 20 km in the main river channels, and up to 20 km and 35 km in the paddy field, respectively. The simulated salinity intrusion results were then used to compute durations of available water for irrigating rice cropping. The results indicate that area where triple rice crops are possible, will be reduced by approximately 71,000 and 72,000 ha, while single crop areas will be increased by approximately 38,000 and 179,000 ha for the mid-2030s and mid-2090s scenarios, respectively. Using GIS techniques the delta was divided into three areas reflecting different rice crop vulnerability levels; areas of high and medium vulnerability measured approximately 200,000 ha and 400,000 ha, respectively.

Simulated Impacts of Climate Change on Current Farming Locations of Striped Catfish (Pangasianodon hypophthalmus; Sauvage) in the Mekong Delta, Vietnam

“…We assessed the impacts of water level and salinity intrusion along the Tien and Hau branches of the Mekong river in time and space by applying model-based scenarios for sea level rise and reduced river flow (e.g., Alcamo et al 1998;Wassmann et al 2004;Hoa et al 2007Hoa et al , 2008Khang et al 2008). …”

“…This process was more complicated compared to the calibration of the hydrodynamic module, because the saline water spreads under influence of the density of the water network with its dams and sluices, and of the dispersion coefficient which depends on flow velocity and also on wind conditions (Khang et al 2008). Table 1 and Fig.…”

“…The calibration process of the hydrodynamic module was performed by adjusting model parameters such as the initial water level in rivers and canals together with Manning coefficients of canal and river segments (Wassmann et al 2004;Khang et al 2008). Figure 2 shows the comparison between the computed and observed water level and water discharge at Tan Chau and Vam Nao (in upstream part of the delta) and Tan An (in the coastal part) (c.f.…”

“…Hoa et al (2007Hoa et al ( , 2008 used an integrated hydraulic model, HydroGis, in tracking the impact of sea level rise and flooding in general. Khang et al (2008) simulated changes in water flow and salinity intrusion for two sea level rise scenarios (?20 and ?45 cm) by using the MIKE11 model and a GIS.…”

Statistical downscaling with Bayesian inference: Estimating global solar radiation from reanalysis and limited observed data

“…However, it is often difficult to obtain long-term SR data, especially in developing countries. The lack of SR data hinders various climate applications in agricultural and hydrological sectors, including the assessment of climate change impacts on the paddy rice production and hydrological regime along the Vietnam Mekong Delta area Khang et al, 2008). To fill the gap between the needs and availability of SR data, global reanalysis data provided by the world's major weather forecast centres (e.g.…”