Southeast Asia & the Pacific: Persistent water surplus in Indonesia

Southeast Asia & the Pacific: Persistent water surplus in Indonesia

23 September 2021

THE BIG PICTURE
The 12-month forecast through May 2022 indicates water surpluses of varying intensity in many regions of Myanmar, extreme in the southwestern states. Surpluses in the nation’s long southern extent will reach into pockets of Thailand while northeastern Thailand can expect moderate deficits.

Moderate surpluses are forecast in northeastern Laos, but anomalies in the south will be exceptional. Extreme surpluses are expected in Cambodia east of the Mekong River, downgrading as they reach through Vietnam’s Central Highlands but intense approaching the Mekong Delta.

In Indonesia, surpluses in Banda Aceh at the northern tip of Sumatra will be intense, but deficits are forecast in a pocket around the metropolis of Medan. Western Indonesian Borneo will see moderate surpluses, and moderate to severe anomalies are forecast for Sulawesi’s northern arm, the Maluku Islands, and the Bird’s Head Peninsula (Doberai) of New Guinea. Surpluses will reach extreme intensity in the Lesser Sunda Islands. Widespread surpluses are forecast throughout southern Papua, Indonesia and the central New Guinea Highlands, extreme in south Papua and a pocket in the Highlands.

Some pockets of surplus, primarily moderate are expected in the Philippines.

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

The forecast through November indicates that surpluses will shrink and downgrade in Southeast Asia and the Philippines. Surpluses will linger in Myanmar, particularly in the west where anomalies will be severe to extreme, while transitional conditions are forecast for the center of the country. Some moderate deficits will persist in northeastern Thailand. Moderate to severe surpluses will persist in southern Laos, eastern Cambodia, and central and southern Vietnam.

Surpluses, primarily moderate will be widespread in Borneo, Sulawesi, and the Maluku Islands, and moderate surpluses are expected in pockets of Sumatra and Java. Extreme to exceptional surpluses are forecast for the Lesser Sunda Islands. New Guinea can also expect surpluses, moderate overall but extreme in southern Papua, Indonesia. Intense deficits are forecast in a pocket of Papua New Guinea south of the Fly River.

From December 2021 through February 2022, surpluses will continue to shrink in Southeast Asia, persisting from eastern Cambodia into Vietnam and southern Laos, as some mild deficits emerge. Transitional conditions (pink/purple) are forecast in Myanmar. Surpluses will shrink considerably in Pacific regions. Anomalies, primarily moderate are forecast for Sulawesi’s northern arm, the Maluku Islands, the Lesser Sunda Island, and pockets of New Guinea. Mild deficits will emerge in Sumatra. Deficits in Papua New Guinea near the Fly River will retreat.

The forecast for the final months – March through May 2022 – indicates that surpluses will persist from eastern Cambodia into Vietnam and will re-emerge in pockets of Myanmar. Surpluses will shrink in the Pacific, lingering though downgrading in Sulawesi’s northern arm, the Lesser Sundas, and along New Guinea’s southern coast. Mild to moderate deficits are forecast for pockets of Malaysia, Sumatra, Java, central Sulawesi, and western Borneo.

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

IMPACTS
In late August, heavy rainfall caused landslides and mudflows that claimed five lives in North Sumatra Province, Indonesia.

In September, two deaths were reported after flash floods struck Indonesia’s East Nusa Tenggara Province in the Lesser Sunda Islands. Flooding hit several regions of Borneo as well, affecting 14,000 people and damaging homes, schools, businesses, and health facilities. Floodwaters reached 1.2 meters (nearly 4 feet) in Lamandau Regency.

Monsoon rains caused flooding in central Thailand that affected 320,000 people, though overall damage was relatively minor. In Bangkok, however, floodwaters reached nearly a meter at the nation’s oldest industrial park, temporarily shuttering three factories and two warehouses at an electronics exporter whose losses could total 900 million baht (~USD$26 million). Retention ponds built to absorb rainwater in the flood-prone industrial region are no longer adequate after years of groundwater extraction have caused the factory-dense complex to sink below sea level.

Thailand’s Pattaya Bay resort region also experienced flooding after heavy rains submerged local roads under 30 to 70 centimeters (12 to 27.5 inches) of water, causing a portion of one to sink 5 meters (16 feet), dragging trees and traffic lights into the depths.

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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