Southeast Asia & the Pacific: Gradual transition from water surplus to deficit

26 September 2017

The Big Picture
The 12-month map (below) indicates a large block of exceptional water deficit in western Cambodia. Exceptional surpluses are forecast in western Myanmar and along the northern stretches of the Salween River, eastern Thailand, Laos, and Southeast Sulawesi, Indonesia.

Moderate to extreme deficits are expected in central Papua New Guinea, and deficits of generally lesser severity are forecast for Malaysia, north and south Sumatra, Java, and Borneo’s southwestern coast. Surpluses of varying intensity are forecast for northern Vietnam, central Thailand, central Philippines, the northern arm of Sulawesi, the Maluku Islands (Moluccas), and western regions of Papua, Indonesia.

Impacts
Flooding in Laos last month killed 10 people, affected over 250,000, and caused property damage of 55.5 billion kip (US$6 million). Farming communities are struggling with poverty in the flood's aftermath, with loss of crops and livestock impacting debt repayment. The northern province of Oudomxay incurred some of the worst damage.

A tropical storm in mid-September caused flooding and landslides around Manila, Philippines that closed schools, financial markets, and government offices, and canceled or diverted 21 flights. At least four people were killed and six remain missing. Alabat in Quezon Province recorded 528 mm (20 inches) of rain in 24 hours.

The Thai government is considering a Bt200 billion (US$6 billion) water management plan devised by the National Water Resource Committee to prevent flooding and drought in the Chao Phraya River Basin. Tropical Storm Doksuri has left many parts of Thailand inundated by floodwaters, creating excessive capacity in some dams and forcing officials to order controlled discharges.

Farmers in Kampot Province, Cambodia are watching their seedlings and rice paddies dry up, with no rainfall in weeks, and are worried about the possibility of famine, loss of livelihood, and the disintegration of communities.

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

With the exception of western Cambodia which has experienced exceptional water deficits, the map progression above indicates a gradual transition in the region away from intense water surplus to deficits of varying severity.

The September through November map shows a significant retreat of water surplus. However, exceptional surpluses are forecast for western Myanmar and northwestern and southwestern Laos. Severe surpluses are forecast for northern Vietnam and the Central Highlands in the south, and eastern Myanmar. Scattered, primarily moderate surpluses are forecast for Indonesia. Near-normal water conditions are expected in the Philippines, Borneo, much of Sumatra, and central Papua. Primarily moderate deficits are forecast to emerge in Thailand, the Malay Peninsula, southern Sumatra, and Java. Exceptional deficits in Papua New Guinea will downgrade to moderate.

From December through February, surpluses in western Myanmar and in Laos will transition to conditions of both deficit and surplus as deficits emerge. The block of exceptional deficits in western Cambodia will diminish somewhat in extent but intense deficits will persist. Moderate deficits will continue to emerge in Thailand, the Malay Peninsula, Sumatra, and Java, and deficits will emerge throughout much of Borneo and Sulawesi, including small pockets of extreme deficits.

After February deficits in Malaysia and Indonesia are expected to become more intense.

(It should be noted that forecast skill declines with longer lead times.)

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.