Future rainfall and long-term forecasts of water supply for rice production using the InVEST model

What is it about?

Water resources of the Mekong River support more than 60 million people in the Lower Basin (LMB) in southeast Asia. The food, water, and energy nexus is critical for food security—especially rice production—and economic security of the region. We forecasted water yield under near- and long-term climate scenarios that drive temperature and rainfall to assess potential impacts on rice cultivation. The InVEST model (Integrated Valuation of Ecosystem Services and Tradeoffs) forecasted water yield, and land evaluation was used to delineate suitability classes for rice cultivation. Greatest rice reduction was predicted for Thailand, followed by Lao PDR and Cambodia, and was stable for Vietnam. Rice production in the LMB appears sufficient to feed the LMB population in 2030, while rice production in Lao PDR and Cambodia are not expected to be sufficient for domestic consumption, largely due to steep topography and sandy soils as well as drought.

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Why is it important?

Pattern-downscaled climate data were specially generated for the LMB. Predicted annual water yields for 2030 and 2060, derived from a drier overall scenario in combination with medium and high greenhouse gas emissions, indicated a runoff reduction of 9–24% from baseline (average 1986–2005). In contrast, increased seasonality and wetter rainfall scenarios increased annual runoff by 6–26%. Extreme drought decreased suitability of transplanted rice cultivation by 3%, and rice production would be reduced by 4.2 and 4%, with and without irrigation projects, relative to baseline. We discuss four adaptation measures to minimize climate impacts: irrigation, changing the planting calendar, new rice varieties, and alternative crops.