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
10:24 - 15/03/2018
CGIAR is carrying out Research Program on Water, Land and Ecosystems for some project groups, namely MK31, MK32, MK33 projects. MK 33 project is expected to contribute to addressing the important challenges in the field of water resources of the Red River Basin. In collaboration with them, I am researching on climate change impacts on water resources in the basin. This study will present how climate change impacts on river flow regimes in the&
CGIAR is carrying out Research Program on Water, Land and Ecosystems for some project groups, namely MK31, MK32, MK33 projects. MK 33 project is expected to contribute to addressing the important challenges in the field of water resources of the Red River Basin. In collaboration with them, I am researching on climate change impacts on water resources in the basin. This study will present how climate change impacts on river flow regimes in the near future (2015-2035) in the Red River Delta with Nhue-Day river basin being selected for a case study, using outputs from state-of-the-art high resolution climate models (belonging to Coupled Model Inter-comparison Project – Phase 5, IPCC). This basin is extremely important and plays a vital role for the socioeconomic development of Vietnam.
- Red River Basin
The Red River begins in China's Yunnan province and flows through Laos before entering Vietnam. The river basin covers an area of 169,020 km2, of which 87,840 km2 are in Vietnam to which the Red River Delta belongs. The area of Red River Delta is approximately 17,000 km2, covering 26 provinces and many important cities of northern Vietnam, including the Hanoi Capital Region.
Figure 1. Overview of Red River Basin
Increasing economic development has resulted in a dramatic rise of water demand in the delta in recent years. In 2009, the water demand was estimated to be 24 billion m3. The number is expected to increase to 31 billion m3 in 2020 and 36 billion m3 in 2050 (Hoa, Tran Dinh, 2010).
In addition, other factors, such as population growth, deforestation, changes in land use, reservoir construction, and climate change, adversely affect water resources. Of these, climate change is a crucial factor, as it redistributes the availability of water resources. Thus, it is more likely that this area significantly lack water supply in the near future.
- Impacts of climate change on water resources
Climate change, as a result of global warming, will lead to more precipitation because of the greater amount of vapour in the atmosphere. The changes in precipitation over land, however, will differ in time and space. It is more likely that extra-tropical zones will get more precipitation while a tendency of decreasing precipitation is projected for sub-tropical regions. In the tropics, precipitation maxima in the wet seasons will increase, while lower precipitation is projected in dry seasons (Do Hoai Nam, Keiko Udo and Akira Mano, submitted to IAHR-APD Congress, 2014). This puts the future availability of water resources at risk.
Figure 2. Linkage between climate change and water resources.
In recent years, the water level in the Red River has significantly decreased in dry seasons while it remains very high in wet seasons.
Figure 3. Water on Red River in dry season (Hoa, Tran Dinh, 2010)
Most studies relevant for the Red River on the potential impacts of climate change on water resources have been based on the information of the Fourth Assessment Report on Climate Change (IPCC, Climate Change 2007: The Physical Science Basis, 2007) even though the last GCMs have been changed in the Fifth Assessment Report on Climate Change that has been published recently (IPCC, The Physical Science Basic, 2014). Policy-makers also continue to count on the assumption that historical conditions will persist into the future. Thus, it is crucial to equip water resources managers, policy makers and planners with a better understanding of changes of water resource characteristics in the context of climate change.
- Assessment of climate change on water resources
The Nhue-Day river basin, a sub-basin of the Red River Basin, Vietnam, has been chosen as a case study for assessing changes in flow regimes. This basin is approximately 114 kilometres in length, covering five northern provinces of Phu Tho, Vinh Phuc, Hoa Binh, Ha Nam and Hanoi, with a drainage area of 7.665 km2. The basin is often adversely affected by tropical cyclones from the northwest Pacific Ocean to South China Sea, and, as observed data have shown, flood and drought frequencies have increased dramatically in the recent years.
Figure 4. Locations of the study area, regional boundary and rain-gauges (▲).
To perform rainfall-runoff analyses, this study will utilize rainfall and river flow information derived from a relatively coarse hydro-meteorological observation network. The network includes nine rain gauges and nine stream gauges that provide daily records of rainfall, river flow and stage. Hydro-meteorological data will be collected for the period 1970-2007, while the output of appropriate climate models will be used for running the hydrological model.
For an impact assessment, selecting less complex hydrological models, which can accommodate the insufficient information of a future watershed, is most preferable. In this study, a rainfall-runoff model HEC-HMS (US Army Corps of Engineers, March 2000) will be employed to simulate the river flow.
Studies on climate change impacts are subject to uncertainties caused by the uncertainties in the estimations of the rainfall, and the structure and parameter estimates of the hydrological model. Recent studies, however, have stated that the most significant source of uncertainties in flow studies is the precipitation estimate resulting from limitations in defining emission scenarios, the climate model structure, the downscaling method and the interval variability of the climate system (Do Hoai Nam, Keiko Udo and Akira Mano., 2013b). It was found that uncertainties from climate model formulations dominate those from the other sources. In order to address this, in this study, the uncertainties in a rainfall estimate will be assessed using multi-model simulations. This method helps to determine the range of uncertainty of the projected results induced by errors in model formulation.
- Expected outputs and outcomes
One of the main outputs will be the identification of the changes in the rainfall at Nhue-Day river basin in the near future (2015-2035). The knowledge of these changes is fundamental for evaluating changes of flow regime in this area. This result will contribute to a better and comprehensive understanding of the changes of river flow regimes in both time and space. Ultimately, this will help water resources-related exploitation and management organizations to propose efficient adaptation actions.
Hanoi, January 25, 2016
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.
Hoa, Tran Dinh. (2010). Water demand and position chosen for a construction ragulating water level on Red River. Water Resources (VIWARA), 7.
IPCC. (2007). Climate Change 2007: The Physical Science Basis. Cambridge: Cambridge Univ.
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.