Southeast Asia and the Pacific: Surpluses continue in Maritime SE Asia

Southeast Asia and the Pacific: Surpluses continue in Maritime SE Asia

24 March 2025

THE BIG PICTURE

The forecast for the 12-month period ending in November 2025 indicates that while most extreme to exceptional surpluses in Maritime Southeast Asia will resolve, regions of Indonesia and the Philippines will observe surpluses of varying intensity. Moderate to extreme deficits are expected in regions of Sumatra, as well as northern Laos and Vietnam. 

Severe to extreme deficits are expected in:

  • Northern Laos, throughout regions near the Nam Ha National Bio-Diversity Conservation Area.

  • Northern Vietnam, throughout most regions northwest of the city of Hanoi. 

  • Indonesia, mostly appearing in the North Sumatra region. 

Severe to exceptional surpluses are anticipated in: 

  • Indonesia, throughout West and East Nusa Tenggara. Northern portions of Sumatra, in the Aceh province, will experience moderate to extreme surpluses, as will North Kalimantan and northern Brunei.

  • Philippines, appearing in central islands of the country, as well as in northern coastal regions of the island of Luzon. 

  • Southern Papua, throughout the Merauke Regency.

The 3-month maps (below) show the evolving conditions in more detail. 

FORECAST BREAKDOWN

The forecast through May 2025 indicates that most extreme to exceptional surpluses in Maritime Southeast Asia will resolve, though several regions are expected to observe moderate to severe surplus. These regions include the majority of the Philippines, East and West Nusa Tenggara, and southern portions of Papua and Papua New Guinea. Northern Brunei is expected to observe moderate surpluses. Pockets of severe to extreme deficits are anticipated in central and southern areas of Thailand, southern Sumatra, Central Kalimantan, western coastal regions of Java’s Banten province, and Papua New Guinea’s West New Britain province. In Vietnam, regions within the Cao Bang province should expect moderate to extreme deficits. 

From June through August 2025, moderate to severe deficits are expected in several regions of Maritime Southeast Asia. These regions include the Indonesian islands of Sumatra, Sulawesi, North Kalimantan, and northern Brunei. Moderate to severe deficits are also anticipated in Malaysia, near the city of Kuala Lumpur. Moderate to severe surpluses will continue in East and West Nusa Tenggara. Mainland Southeast Asia is expected to observe near-normal conditions. 

The forecast for the final months – September through November 2025 – indicates that most moderate to severe deficits in Maritime Southeast Asia will dissipate. Moderate surpluses are expected to occur in Java and in West and East Nusa Tenggara. Moderate to severe deficits are expected to arise in southern Vietnam and southern Cambodia. 

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
On March 4th, thousands of people were evacuated from Indonesia’s capital, Jakarta, as torrential rain caused destructive flooding throughout the city. Floodwaters rose to 3 meters, immersing roads, cars, and homes. Though the greater metropolitan area of Jakarta typically sees floods, the current situation is reportedly the worst since 2020, in which 60 deaths were caused by the floods.  

Following the flooding of Jakarta, former director of the World Health Organization (WHO) Southeast Asia Infectious Diseases, Tjandra Yoga Aditama, reminded the public of health risks following floods. He reiterated the importance of maintaining hygiene in order to prevent the spread of disease caused by contaminated water. Aditama stated the most common infectious diseases after floods, as well as a specific warning for the spread of leptospirosis. "Leptospirosis can cause kidney and liver disorders if not treated quickly,” said Aditama.

Vietnam’s coffee harvest for 2024-2025 is expected to decrease by 10 to 20 percent as drought and high temperatures worsened by El Niño threaten local crop health. Key agricultural areas, such as the Central Highlands, suffered extreme damage as trees continue to lose foliage and crop yields. This potential decrease follows the significant decline in crop yields during the 2023-2024 season, which dropped by 20 percent compared to the year prior.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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Many analyses reported in ISciences-authored blog posts are based on data generated by the ISciences Water Security Indicator Model (WSIM). Other sources, if used, are referenced in footnotes accompanying individual posts. WSIM is a validated capability that produces monthly reports on current and forecast global freshwater surpluses and deficits with lead times of 1-9 months at 0.25°x0.25° resolution. This capability has been in continuous operation since April 2011 and has proven to provide reliable forecasts of emerging water security concerns in that time-frame. WSIM has the ability to assess the impacts of water anomalies on people, agriculture, and electricity generation. Detailed data, customized visualizations, and reports are available for purchase.

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