How is climate change expected to impact on water resources in the Red River Basin?

How is climate change expected to impact on water resources in the Red River Basin?

How is climate change expected to impact on water resources in the Red River Basin?

11:07 - 19/03/2018

RESEARCH ON THE SCIENTIFIC AND PRACTICAL BASIS TO HARMONISE WATER ALLOCATION WITH WATER TREATMENT FOR IRRIGATION SYSTEMS IN THE RED RIVER DELTA
Community based water quality monitoring: a multi-benefit approach to water governance in the Red river basin, Vietnam
Small-scale irrigation – effective solution for sloping land areas
Assessment of climate change impacts on river flow regimes to support decision-making in water resources management in The Red River Delta, Vietnam – A case study of Nhue-Day River Basin
Impact of existing water fee policy in the Red River Basin, Vietnam

Global warming has led to changes in the variability of temperature and precipitation. As a result, it is expected that river flow regimes will be accordingly changed. This study presents how climate change might impact on river flow regimes in the Red River Delta in the near future (2015-2035) with Nhue-Day river basin being selected for a case study, using outputs from multiple state-of-the-art high resolution climate models.

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Summary

Global warming has led to changes in the variability of temperature and precipitation. As a result, it is expected that river flow regimes will be accordingly changed. This study presents how climate change might impact on river flow regimes in the Red River Delta in the near future (2015-2035) with Nhue-Day river basin being selected for a case study, using outputs from multiple state-of-the-art high resolution climate models.

Recommendations

  • Each climate model predicts different precipitation volumes with varying distribution in space and time. As a consequence, simulated flows from hydrological modelling are also different. Hence, the climate simulation results from different models should be combined to better represent overall changes. Based on this, more reliable probability forecasts for extreme events can be provided. Aggregated results from hydrological modelling with the input of all available regional climate models showed that flow might significantly increase in the wet season while it will slightly decline in the dry period. This suggests that flood risk will increase during the rainy season whereas during the dry season drought risk will be aggravated in the future.
  • Along with population growth, socioeconomic development and rapid urbanization, these changes will further increase the pressure on sustainable water resources exploitation, use and management in the near future.

The existing problems

Climate change is believed to be one of the predominant challenges for mankind in the 21st century. It has been resulting in immense adverse effects on human and natural systems over the world. For example, a decline of agriculture production and growing risk of animal and plant extinction are triggered by rising temperatures; destruction of infrastructure and loss of lives frequently happening due to severe flood events; besides, severe droughts are leading to water conflicts and wars. A regional assessment of climate change on mankind, to some extent, was addressed in the Fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC, 2014).

The assessment of climate change impacts on hydrology has been addressed for years. It has been constantly updated thanks to the improvement of climate model outputs regarding spatiotemporal resolution and projection capability. Most estimations have been based chiefly upon coupling method between global atmospheric general circulation models (GCMs), which are set up to simulate past and current climate and then used to project the future state of global climate with specifically greenhouse gas emission scenarios, and hydrological models. Although climate models could be expected to project correctly trends, different climate models might give different outputs. In other words, application of various climate model output often results in the discrepancies of runoff simulations. Assessment of climate change impacts with multi-climate models has been exhibited a cost-effective method to determine the scope of project in the Coupled Model Inter-comparison Project (CMIP).

Vietnam is one of the nations most impacted by climate change. To develop adaptation strategies to climate change, the evaluation of future river flow change on river basin scale can provide decision makers and exposed communities with essential information for water resources management. This study presents a projection of short-term runoff change in Nhue-Day river basin as a case study. The precipitation prediction for the period of 2026-2035 from an ensemble of climate models was used as input for a distributed hydrological model to estimate flow fluctuation.

How is climate change expected to impact on water resources in the Red River Basin?

In my research, runoff simulations based on the ensemble of three climate model scenarios are conducted by using the HEC-HMS rainfall-runoff model. Simulated hydrographs for the period 2026 to 2035 are compared to the observed discharge in the baseline period (1979-2003).

The simulation results indicate that the monthly mean discharge will show a strong variability for the period (2036-2035), particularly in the wet season. This range of variation fluctuates between -500 and 1700 m3/s whereas the monthly mean runoff in dry season varies from -150 to 150 m3/s. Furthermore results suggest that the monthly mean discharge will increase in the wet season (May-September) and nearly remains unchanged during the dry season (Fig. 1).


Figure 1.
Changes between the baseline (79-03) and simulated results in monthly mean discharge.

Policy implications

As the results showed, it is expected that disasters related to climate extremes – as droughts, floods, salt water intrusion and erosion - will occur more frequently in the future. To solve this problem, water related policy-makers should be aware of the urgent need for climate change adaptation and corresponding mechanisms to manage water resources well to ensure adequate quality and quantity. For this purpose, more effort should be undertaken to monitor climate and water as well as to establish comprehensive data sets and management for future forecasts.

 

 

Conclusion

The assessment of climate change impact on river flow regime, by employing a rainfall-runoff model based on the precipitation simulated by climate models, might imply uncertainties depending on the climate model. However, in this study, the estimation was based on the rainfall projected by an ensemble of climate models. This provided a range of variation in river flow, which allowed an understanding of the range of uncertainty.in prediction results.

The results showed that the monthly mean discharge is expected to increase in the wet but little change for the dry season (May-September), which puts water resources and some other related sectors at risk. High variability in results suggest an increase in extreme events both in floods and droughts.   . In addition to sea level rise, the low stream runoff in dry season will widen further inland salinity intrusion, which damages cultivable regions. Besides, water shortage might also raise level of water conflicts. Otherwise, the rise of water discharge in the wet season accompanied by the change of land use and increasingly growth of urbanization processes will raise danger of flooding which might destroy anything on its path.

Ultimately, this will help water resources-related exploitation and management organizations to propose efficient adaptation actions.

Hanoi, September 26th, 2016


 

Bibliography

Do Hoai Nam, Keiko Udo and Akira Mano. (2013b). Assessment of future flood intensification in Central Vietnam using a super-high-resolution climate model output. Journal of Water and Climate Change, doi:10.2166/wcc.2013.088.

Do Hoai Nam, Keiko Udo and Akira Mano. (submitted to IAHR-APD Congress, 2014). Change in extreme rainfall indices over Vietnam, assessed using global super-high resolution climate model outputs. Journal of Hydrology.

IPCC. (2007). Climate Change 2007: The Physical Science Basis. Cambridge: Cambridge Univ.

IPCC. (2014). Climate Change 2014: Mitigation of Climate Change. Cambridge and New York: Intergovernmental Panel on Climate Change.

IPCC. (2014). The Physical Science Basic. Geneva, Switzerland: Geneva.

US Army Corps of Engineers. (March 2000). Hydrologic Modeling System HEC-HMS. New York: Hydrologic Engineering Center.