Southeast Asia & the Pacific: Water surpluses will downgrade

Southeast Asia & the Pacific: Water surpluses will downgrade

25 October 2021

THE BIG PICTURE
The 12-month forecast through June 2022 indicates water surpluses of varying intensity in many regions of Southeast Asia. Anomalies will be extreme to exceptional in the Mekong River Watershed through southern Laos, Cambodia, and Vietnam, and widespread though less intense elsewhere in those nations.

Surpluses will also be widespread in Myanmar, extreme in the southwestern states and extreme to exceptional in the southeast leading into Thailand. Surpluses in central and southern Thailand will be moderate overall.

Moderate surpluses are forecast in many pockets in the Philippines.

In Indonesia, Banda Aceh at the northern tip of Sumatra can expect intense surpluses. Surpluses of varying intensity are forecast in Western Indonesian Borneo and in the north. Moderate to severe anomalies are forecast for Sulawesi’s northern arm and southeastern leg, the Maluku Islands, the Lesser Sunda Islands, and the Bird’s Head Peninsula (Doberai) of New Guinea. Widespread surpluses are forecast throughout southern Papua, Indonesia, the Highlands region of Papua New Guinea, and scattered pockets along the coast of the Papuan Peninsula.

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

The forecast through December indicates that surpluses will shrink slightly but remain widespread, though the extent of intense anomalies will shrink. In Myanmar, surpluses will shrink in the north and east but persist elsewhere, particularly in the west where anomalies will be extreme, while transitional conditions are forecast in parts of the Middle Irrawaddy River and between the Myittha and Chidwin Rivers. Deficits will retreat from Thailand and surpluses will persist, primarily in central regions. Extreme to exceptional surpluses will persist from southern Laos through eastern Cambodia in the Mekong River region, and severe anomalies are expected in Vietnam’s Central Highlands. Surpluses of generally lesser intensity are forecast in many other regions of Vietnam and Laos.

In the Philippines, mild to moderate surpluses are forecast in central and southern regions. Surpluses will shrink and downgrade in Malaysia and Sumatra, but remain widespread in much of Indonesian Borneo, Sulawesi, and the Maluku Islands. A pocket of deficit will persist on Peninsular Malaysia’s northeastern coast. Moderate surpluses are forecast at either end of Java, and severe to exceptional surpluses in the Lesser Sunda Islands. Deficits will nearly disappear in New Guinea while surpluses in the Bird’s Head Peninsula elevate to severe and surpluses from southern Papua, New Guinea into the center of the island moderate. 

From January through March 2022, transitional conditions will increase in Myanmar as surpluses shrink, but many areas of surplus will persist elsewhere in Southeast Asia and anomalies will remain extreme to exceptional from southern Laos into Cambodia in the Mekong region. In the Philippines, some pockets of moderate surplus are forecast in the central islands and Mindanao. Surpluses will retreat from Malaysia, Indonesian Borneo, Sumatra, and Java as some mild deficits emerge. Surpluses will also retreat from southern Sulawesi while anomalies in its northern arm shrink and downgrade. Surpluses will shrink and moderate in the Lesser Sunda Islands, the Malukus, and New Guinea.

The forecast for the final months – April through June 2022 – indicates that surpluses will re-emerge in western and southern Myanmar and moderate surpluses will linger in central Thailand, from the Central Highlands of Vietnam into Cambodia, the central Philippines, northern Sulawesi, the Lesser Sunda Islands, and pockets along New Guinea’s southern coast. Mild to moderate deficits are forecast for pockets of Malaysia, Sumatra, Java, and western Borneo.

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

IMPACTS
Mid-September brought heavy rainfall to Vietnam, triggering floods that resulted in at least two deaths. The storm unleased 908 mm (35.7 inches) of precipitation on Quang Ngai Province. Torrential rain pounded the nation’s central region in October, killing one person and prompting evacuation of 4,500.

The Batusitanduk River in South Sulawesi, Indonesia overflowed in early October after heavy rains. The downpour caused flooding and landslides that claimed four lives in the region. Damage was reported to homes, schools, and public buildings in Kalimantan, Borneo as well.

Since late September, 18 people have drowned in Thailand due to flooding, including one motorcyclist who was swept into the powerful current of a flooded underpass in Nakhon Ratchasima. Rail travel was suspended in the central province of Saraburi. In Sukhothai province, flooding forced closure of the local hospital’s emergency room for three days as floodwaters reached over a meter (39 inches) deep.

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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