Southeast Asia & the Pacific: Exceptional water surplus forecast on Lower Mekong

22 October 2020

THE BIG PICTURE
The 12-month forecast through June 2021 indicates some water deficits in western Thailand and in Cambodia from Tonlé Sap Lake to the coast.

Much of the rest of Southeast Asia can expect surpluses. In Myanmar, surpluses of varying intensity are forecast for nearly all the country and will be exceptional along the Salween River and extreme to exceptional from the Irrawaddy River to the west coast. Surpluses will also be intense from eastern Cambodia into southern Vietnam and southern Laos, and in northwestern Vietnam. Northern Laos can expect severe surpluses, and generally moderate surpluses are forecast for peninsular Myanmar, peninsula Thailand, and pockets in eastern Thailand.

ISciences_Southeast_Asia_Composite_Adjusted_202007-202106_12mo_twitter.png

Scattered surpluses are forecast throughout Indonesia including Sumatra’s northern tip, pockets of Borneo, Flores Island, and from northern Sulawesi through the western portion of the Bird’s Head Peninsula (Doberai Peninsula) in Papua, Indonesia and along Papua’s southern coast. In Papua New Guinea, surpluses are expected in a pocket of the central New Guinea Highlands and along parts of the southern coast including the Bird’s Tail Peninsula (Papuan Peninsula). Anomalies will be extreme in northern Sulawesi and the Bird’s Head Peninsula. Moderate deficits are forecast for the Baram River region in Malaysian Borneo and into Brunei. Surpluses are also forecast for the central Philippines and anomalies will be extreme on Negros Island.

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

The forecast through December indicates that deficits in Southeast Asia will nearly disappear with a few isolated pockets persisting in northwestern Thailand. A pocket of deficit will emerge on peninsular Malaysia’s central east coast. Surpluses are expected in nearly all of Vietnam and Laos and in eastern Cambodia. Anomalies will be exceptional on the Mekong River through Cambodia and Vietnam. Mixed conditions are forecast in Myanmar with intense surpluses west of the Irrawaddy River, surpluses of generally lesser intensity in the north and east, and transitional conditions (pink/purple) in the center of the nation and the Irrawaddy Delta.

ISciences_Southeast_Asia_Composite_Adjusted_202007-202106_3mo_twitter.png

In Indonesia, surpluses will shrink and downgrade overall but will remain widespread from southern Borneo into Papua, Indonesia and in the Lesser Sunda Islands. Anomalies will reach extreme intensity in some pockets. Deficits in New Guinea will nearly disappear. Moderate surpluses are forecast for the central Philippines.

From January through March 2021, widespread surpluses will persist in Laos, Vietnam, and eastern Cambodia. Exceptional surpluses will downgrade but anomalies will be extreme from eastern Cambodia into Vietnam. Nearly normal conditions are expected in Thailand with a few isolated pockets of surplus and of deficit. Transitional conditions are forecast for many regions of Myanmar along with lingering areas of surplus. Deficits, primarily moderate, will emerge in Malaysian Borneo and central Sulawesi. Surpluses will shrink considerably in Indonesia and Papua, Indonesia leaving pockets in northern Sulawesi, Flores Island, the Maluku Islands, and Papua. Moderate surpluses will emerge along parts of Papua New Guinea’s southern shore, and moderate surpluses are forecast for the central Philippines and pockets in the north.

The forecast for the final months – April through June 2021 – indicates surpluses in pockets of Vietnam, western Myanmar, the central Philippines, and New Guinea’s southern shore. Deficits will emerge in Malaysia, Sumatra, Java, and a few other isolated pockets in Indonesia.

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

IMPACTS
October brought destructive precipitation to many areas of Southeast Asia.

Flooding and landslides triggered by heavy rainfall claimed the lives of 111 people in central Vietnam with dozens still missing. Related damages include crop loss on 7,200 hectares of agricultural land and the death of 691,000 cattle and poultry. Many major highways as well as rural roads were compromised. An estimated 250,000 households were affected and many areas remain under 2 to 3 meters (6.6 to 9.8 feet) of water.

In Cambodia, at least 12 flood-related deaths have been reported as the country struggles with torrential rainfall that has affected 30,000 households. In an effort to mitigate anticipated damage, authorities planned releases from reservoirs in Sa Kaeo province, and 1,600 prisoners in Banteay Meanchey Province have been evacuated. An estimated 120,000 hectares of farmland are flooded including 80,000 hectares of rice.

Thailand’s Nakhon Ratchasima Province northeast of Bangkok suffered flooding in the Pak Chong District as runoff from a national park caused a canal to overflow, inundating roads, offices, houses, temples, and farmland.

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.

Subscribe to our monthly Water Watch List

Search blog categories

Search blog tags