Southeast Asia & the Pacific: Water surpluses forecast in Indonesia

Southeast Asia & the Pacific: Water surpluses forecast in Indonesia

21 July 2020

THE BIG PICTURE
The 12-month forecast through March 2021 indicates moderate to extreme deficits in much of western Thailand reaching across the border into southern Myanmar. Deficits of similar intensity are forecast for eastern Thailand spanning the Mekong River into Laos.

Surpluses of varying intensity are forecast west of the Irrawaddy River in Myanmar. Moderate surpluses are expected in eastern Cambodia and pockets of Vietnam from Da Nang to Ho Chi Minh City; a pocket in southeastern Thailand and pockets in the peninsular regions of Thailand and Myanmar; and northeastern Laos.

Surpluses are also forecast in many pockets of Indonesia. Anomalies will be intense in Aceh Province in northern Sumatra and in eastern Java and Flores Island. Other areas with a forecast of surplus include pockets of Borneo, southern Sumatra and western Java, northern and eastern Sulawesi, many small Indonesian islands, and the Bird’s Head Peninsula (Doberai Peninsula) and other areas in Papua, Indonesia.

In Papua New Guinea, intense deficits are expected around the Gulf of Papua, moderate deficits along the northern coast, and moderate surpluses in the central Highlands. Nearly normal conditions are forecast for the Philippines.

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

The forecast through September indicates that surpluses will shrink and downgrade overall but persist in many areas. In Southeast Asia, surpluses are forecast for western and northern Myanmar; pockets in the Malay Peninsula; southeastern Thailand south of the Mun River; from eastern Cambodia into southeastern Vietnam; and central Vietnam. Deficits ranging from moderate to exceptional will persist in west-central Thailand reaching into Myanmar’s Kayin State, and in northeastern Thailand. Nearby in central Laos, deficits will be moderate. A prior pocket of intense deficit in Cambodia north of Tonlé Sap will transition to surplus, but some pockets of exceptional deficit will emerge to the west near the coast.

Surpluses are forecast in many pockets of Malaysia and Indonesia. Anomalies will be intense at each end of Sumatra and Java and on Flores Island. Intense deficits will emerge on Timor Island. Deficits will shrink and downgrade on New Guinea but remain intense along the western shore of the Gulf of Papua in Papua New Guinea; surpluses are forecast for many other regions on the island. In the Philippines, surpluses will retreat from most of Luzon but increase in Mindanao with moderate anomalies in the east and mild surpluses emerging in the west in prior areas of deficit.

From October through December, water conditions in many parts of the region will normalize. Some generally mild deficits are expected in central Myanmar, western Thailand, and Vietnam’s northwestern corner. Moderate surpluses are forecast for Vietnam’s Central Highlands. Nearly normal conditions are expected in much of Malaysia, Indonesia, the Philippines, and Papua New Guinea, though pockets of surplus are forecast in the smaller islands of Indonesia and on New Guinea. Deficits will nearly disappear in Papua New Guinea.

The forecast for the final months – January through March 2021 – indicates that deficits, generally mild to moderate, will increase somewhat, particularly in Southeast Asia. Some scattered, small pockets of surpluses are forecast, primarily in the smaller islands of Indonesia.

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

IMPACTS
Heavy rainfall in Indonesia’s South Sulawesi province caused flooding that claimed 36 lives with 66 people missing. Three rivers in the region overflowed and nearly 15,000 people were evacuated.

Monsoon rains in Myanmar triggered a mountain landslide in Kachin state that buried at least 160 people at a jade mining site.

Drought in northwestern Thailand has turned the dry riverbed of the Yom River into a playing field for local youth after six months without sufficient rainfall, leaving rice farmers and fisherman in the region facing significant losses. In southern Thailand, reservoirs serving Pattaya’s 100,000 plus residents have dropped to minimum levels, prompting the water authority to reduce tap water distribution by 25 percent. And in peninsular Thailand, the Pran Buri reservoir in Prachaup Khiri Khan has fallen to 25 percent of capacity. With reservoir water being prioritized for human consumption, rice farms in the region may have to forgo irrigation and rely on rainfall.

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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