Southeast Asia & the Pacific: Widespread surpluses throughout

30 November 2022

THE BIG PICTURE
The 12-month forecast through July 2023 indicates widespread, intense water surpluses in much of Southeast Asia, exceptional in many regions. Surpluses are also expected in the Philippines and a number of regions in Indonesia.

In Southeast Asia, surpluses are forecast from Myanmar through Vietnam with widespread exceptional anomalies in eastern Myanmar and eastern Thailand through central Cambodia. The Mekong Delta can expect surpluses of varying intensity and extreme surpluses are forecast in Vietnam’s Central Highlands.

In the Philippines, surpluses of varying intensity are forecast with exceptional anomalies in the Visayas and near Manila.

Surpluses will be moderate to severe in Sumatra but will reach exceptional intensity in West Kalimantan, Indonesian Borneo. Surpluses ranging from severe to exceptional are forecast in Flores Island, Sulawesi’s northern arm, and Seram Island in the Malukus. In Papua, Indonesia, surpluses of varying intensity are predicted for the Bird’s Head Peninsula (Doberai), Farfak Peninsula, and southern Papua.

In Papua New Guinea, a few areas of surplus are expected in the Southern Highlands and southern coastal areas, and a pocket of deficit on the north coast and in nearby small islands.

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

The forecast through January 2023 indicates that widespread surpluses will continue in many areas, but the extent of intense surplus will shrink. In Southeast Asia, surpluses are forecast in Myanmar’s southwest, southeast, and far north but transitional conditions and deficits are expected in the center of the nation. From Thailand through Vietnam surpluses will be widespread, moderate to severe overall but exceptional in the Chi River Basin in Thailand and from eastern Thailand through north-central Cambodia. Moderate deficits will emerge in far northern Laos. In the Philippines, surpluses will be widespread, moderate overall but with severe pockets. Surpluses of varying intensity are predicted throughout Indonesia with intense anomalies in coastal West Kalimantan (Borneo), Sulawesi’s northern arm, eastern Java and pockets in the Lesser Sunda Islands, Seram Island in the Malukus, and southern Papua. In Papua New Guinea, surpluses are forecast in the central Highlands and the Bird’s Tail Peninsula (Papuan Peninsula).

From February through April, normal conditions will return to much of Indonesia and Papua New Guinea, but surpluses will remain widespread in many regions of Southeast Asia and the Philippines. Mixed conditions are forecast for southern and western Myanmar. Surpluses are forecast in southeastern Myanmar, Thailand, Cambodia, several areas in Vietnam (particularly the Central Highlands), and pockets in Laos. Anomalies will be exceptional in the Chi River Basin and from eastern Thailand through north-central Cambodia, intense in southeastern Myanmar, and generally moderate in the Philippines. A few pockets of moderate surplus are forecast in central Indonesia and coastal New Guinea, and small pockets of deficit will emerge in Java and Sulawesi.

The forecast for the final months – May through July – indicates near-normal conditions overall with lingering surpluses in southeastern Myanmar, the Upper Chi River, Vietnam’s Central Highlands, and a few much smaller pockets in the Philippines and Indonesia. Small pockets of deficits are also forecast in Indonesia.

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

IMPACTS
Due to extreme land subsidence from groundwater extraction, the Indonesian government plans to move its capital from Jakarta, located on Java, to Nusantara, on Borneo. More than 60 percent of Jakarta is estimated to be below sea level, with some areas of northern Jakarta experiencing land subsidence from 15 to 25 cm a year (5.9 to 9.8 inches). According to the World Bank, if continued, these areas would sink to 4 to 5 meters below sea level by 2025.

A recent study in Thailand observed increased seedling mortality in tropical forests that are seasonally dry, as a result of severe and prolonged drought. These studies were conducted by scientists from Osaka Metropolitan University for over seven years, and focused on seedlings in a national park in northern Thailand. The study’s findings suggest that future climate change may further affect seedlings thought to be more drought tolerant, as the seedlings studied are historically more resilient to drought than ones found in rainforests.

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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