Southeast Asia & the Pacific: Water deficits will emerge in Sumatra

Southeast Asia & the Pacific: Water deficits will emerge in Sumatra

24 May 2022

THE BIG PICTURE
The 12-month forecast through January 2023 indicates near-normal water conditions in much of Thailand, and generally moderate surpluses in several other regions of Southeast Asia.

Surpluses are forecast through the Irrawaddy River Watershed in Myanmar, becoming intense approaching the delta. Moderate anomalies are expected in northern Laos, Cambodia’s western half, and far northwestern Vietnam. Surpluses are also forecast in Vietnam from Da Nang through the Central Highlands and will be severe in the southern region of the Highlands. Likewise, moderate to severe surpluses are forecast in the peninsular regions of Myanmar, Thailand, and Malaysia, though a small pocket of moderate deficit is expected in Kuala Lumpur.

Widespread deficits ranging from moderate to extreme are forecast in central Sumatra, and surpluses in Banda Aceh in Sumatra’s northern tip.

Widespread surpluses of varying intensity are expected in the Philippines and Indonesia. Anomalies will be severe to exceptional in the central Philippines, Palawan, and northern Mindanao. Though normal water conditions are forecast for most of Malaysian Borneo, surpluses are expected in the north as well as throughout the remainder of Borneo where many pockets of intense surplus are predicted. Elsewhere, areas with exceptional surplus include Java, Bali, Flores Island, Timor, and southern coastal areas of Papua, Indonesia. In Papua New Guinea, surpluses are expected in the west from the Highlands leading through the Fly River region in the southwest. Deficits are forecast in PNG near the Torres Strait in the south and intense deficits along the northern coast and in New Britain.

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

FORECAST BREAKDOWN
The forecast through July indicates that surpluses will shrink and downgrade in Southeast Asia but remain widespread. Greatest attrition will be in Myanmar where surpluses will linger in the far north and along the Salween River in the east; mixed conditions are expected in the Irrawaddy Watershed. Surpluses are forecast in northwestern and southwestern Thailand, northern Laos, western Cambodia, many regions of Vietnam, and the Malay Peninsula. Anomalies will be extreme to exceptional near Da Nang, Vietnam; north of Tonlé Sap, Cambodia; and in Peninsular Thailand. Surpluses are expected in the Philippines, intense in the central islands and Palawan. Peninsular Malaysia and northeastern Malaysian Borneo can expect surpluses as can central and eastern Indonesian Borneo. Other areas with a forecast of surplus include Java, the Lesser Sunda Islands, northern Sulawesi, and much of Papua, Indonesia, into PNG. Deficits will emerge in Sumatra and the Solomon Islands; persist in PNG near the Torres Strait, in the Bird’s Tail Peninsula, and along the northern coast; and increase in New Britain.

From August through October, surpluses will continue to shrink in Southeast Asia with anomalies persisting in Myanmar’s northern tip, Peninsular Thailand, southwestern Cambodia, and much of central Vietnam. Deficits are forecast in a pocket northwest of Mandalay, Myanmar; Vietnam’s northwest corner; and Peninsular Malaysia. Deficits will intensify in central Sumatra becoming extreme to exceptional, while surpluses emerge on the island’s southeastern coast. Surpluses are expected to shrink in the Philippines, persisting mainly in Mindanao, but will increase and intensify throughout Indonesia and PNG and will include exceptional anomalies in Borneo, Java, and southern Papua, Indonesia. Deficits will linger in PNG’s coastal regions and “tail,” and will increase in the nearby islands.

The forecast for the final months – November through January – indicates widespread deficits in Sumatra and Malaysia, and a few pockets in northern Southeast Asia. Surpluses are forecast in central Vietnam, the Philippines, coastal Indonesian Borneo, Java, the Lesser Sunda Islands, Sulawesi, the Malukus, and New Guinea. Deficits will shrink in the Bismarck Archipelago and Solomons.

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

IMPACTS
Late April rainfall brought flooding to several provinces in southwestern Mindanao, Philippines. Residential areas of Talayan, Maguindanao were submerged, power outages reported, and motorists stranded as a provincial road was inundated. In Sultan Kudarat Province, the downpour turned a major motorway into a river.

In early May, flooding in southern Thailand resulted in one death and damages to 350 homes as well as many roads and bridges. Mid-May torrential rainfall triggered flooding in six provinces in the north while in the south Bangkok recorded 125.8 mm (~5 inches) of rainfall in just 24 hours. Flood conditions returned yet again to the nation’s northern regions later in the month bringing the total number of homes damaged during May to over 1,000. In Chaing Rai Province, the Mae Lao River overflowed, severing road access to neighboring Chaing Mai Province.

Several regions of Indonesia also incurred flood and landslide damage after heavy precipitation in May including Sumatra, Java, North and Central Kalimantan, and Gorontalo. Eight villages in South Aceh were swamped and over 11,400 homes damaged in Medan City in Sumatra. Four people died in a landslide in West Java.

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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