Southeast Asia & the Pacific: Water surpluses will shrink considerably

Southeast Asia & the Pacific: Water surpluses will shrink considerably

20 May 2021

THE BIG PICTURE
The 12-month forecast through January 2022 indicates intense surpluses in Java and through the Lesser Sunda Islands. Surpluses will be exceptional in eastern Java, Bali, Flores Island, Timor, and Banda Aceh in Sumatra’s northern tip.

Moderate surpluses are forecast for Borneo’s northern reaches, but anomalies will be more intense in the delta area of the south around the city of Banjarmasin. Elsewhere in the region surpluses are forecast for Sulawesi’s northern arm, the Maluku Islands, the Bird’s Head Peninsula (Doberai Peninsula) in New Guinea and many pockets of the island. Deficits are expected along the western Gulf of Papua and pockets in Sumatra’s northern half.

Surpluses are forecast for the central and southern Philippines, severe to extreme in the center of the country.

Normal water conditions are expected in much of Southeast Asia. Moderate surpluses are forecast in Vietnam’s narrow neck and in the Central Highlands and spanning the southeastern Thai border into Cambodia. A pocket of moderate deficit is forecast in northwestern Thailand and east of Ho Chi Minh City in Vietnam. Myanmar can expect deficits northwest of Mandalay and small pockets of surplus along the southwest coast and in the Lower Irrawaddy region.

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

The forecast through July indicates that surpluses will shrink and downgrade considerably. Extreme to exceptional anomalies will persist in the Lesser Sunda Islands and severe anomalies in the central Philippines. Isolated pockets will persist throughout Indonesia, notably in Banda Aceh in Sumatra’s northern tip. Some moderate deficits will persist on the western Gulf of Papua. In Southeast Asia, surpluses will persist in many regions of Thailand, Cambodia, Vietnam. Anomalies will be moderate overall but more intense in Vietnam’s narrow neck and from northwestern Cambodia into Thailand. Surpluses are also expected in eastern Peninsular Malaysia and Laos’ northeastern spur. In Myanmar, moderate deficits will emerge in a pocket northwest of Mandalay.

From August through October, water conditions in Southeast Asia will be relatively normal though moderate deficits will linger northwest of Mandalay and will emerge in a pocket of northwestern Thailand. The Philippines will normalize as well overall with moderate deficits emerging south of Manila. Many pockets of moderate surplus are expected to emerge in Borneo, Sulawesi, the Maluku Islands, and New Guinea. Extreme surpluses are forecast for Flores Island, but transitional conditions are expected on Timor. Deficits on the Gulf of Papua will intensify south of the Fly River Delta.

The forecast for the final months – November 2021 through January 2022 – indicates moderate deficits in northern and peninsular Southeast Asia and moderate surpluses in the Central Highlands of Vietnam. Surpluses are also forecast for many pockets throughout the smaller islands of Indonesia and on New Guinea, as well as small pockets in the Philippines. Deficits are forecast for pockets of Sumatra and Malaysian Borneo.

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

IMPACTS
Damages from recent flooding in Timor Leste and Indonesia, including destruction from Cyclone Seroja in early April, have now reached an estimated US $200 to $250 million. Experts point to the economic risk of underinsurance, putting Indonesia’s insurance gap - the value of uninsured assets - at around $14.6 billion.

Intense rainfall in mid-May brought flooding to South Kalimantan, Indonesia, as the Satui and Haruyan Rivers overflowed. Floodwaters reached 1.5 meters (nearly 5 feet), damaging at least 555 homes and submerging cropland. Federal flood reliefs monies totaling IDR66 billion (~USD $4.6 million) have been allocated to nearly 4,000 recipients in five districts.

In Thailand, traffic in several metropolitan regions came to a halt as flooding from extreme rainfall covered city streets. Pattaya on the eastern Gulf coast suffered power outages, and motorists in Khon Kaen province in the northeast were stranded when muddy waters submerged a road.

The Davao Airport on Mindanao in the Philippines recorded 265 mm (10.4 inches) of rainfall in just 24 hours on 27 April. In May, several communities in the vicinity of General Santos City, also on the island of Mindanao, experienced flooding as storms swelled creeks and clogged canals.

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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