Southeast Asia & the Pacific: Widespread water surpluses will persist

23 September 2022

THE BIG PICTURE
The 12-month forecast through May 2023 indicates widespread surpluses of varying intensity in many regions of Southeast Asia. Surpluses are also expected in the Philippines and central and eastern Indonesia.

In Myanmar, surpluses of varying intensity are forecast throughout much of the nation with a few pockets of transitional conditions (pink/purple). Though most of northwestern Thailand will see near-normal conditions, surpluses are expected in many remaining areas and will include severe to exceptional surpluses in the Chi River Basin in the east and the Lower Ping River region in the west. Cambodia can expect widespread extreme to exceptional surpluses that will reach well into southern Laos and Vietnam. Surpluses of lesser intensity are forecast in northern regions of Laos and Vietnam.

In the Philippines, surpluses will be intense in the central islands, moderate to severe in northern Mindanao, and moderate in eastern Luzon.

Surpluses will be widespread and intense in West Kalimantan, Indonesian Borneo, and moderate along several rivers elsewhere in Borneo. Surpluses of varying intensity are forecast in Sulawesi, the Lesser Sunda Islands, pockets of Java and Sumatra, the Maluku Islands, and the Bird’s Head Peninsula (Doberai Peninsula), nearby Fakfak Peninsula, and southern extreme of Papua, Indonesia. Anomalies will be especially intense in the Bird’s Head, Fakfak Peninsula, and nearby small islands.

In Papua New Guinea, surpluses are expected in Southern Highlands Province in the center of the nation. Pockets of deficit are forecast on New Guinea’s north coast and nearby small islands.

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

The forecast through November indicates that surpluses will persist in many regions of Southeast Asia and the Pacific. Widespread, severe to exceptional anomalies are forecast from Cambodia into southern Vietnam and Laos. Moderate surpluses are forecast in Thailand’s eastern half and the Lower Ping River region of the west, and in northeastern Laos. Transitional conditions are predicted for central Myanmar and surpluses of varying intensity in many other regions of the nation. In the Philippines, surpluses are forecast in the Visayas and Mindanao. While conditions in Sumatra’s northern half will be primarily normal, surpluses are expected along coastal regions in its southern half and surpluses of varying intensity throughout much of Indonesia, Malaysian Borneo, and Papua New Guinea. Anomalies will be extreme to exceptional in some pockets including from Bali into Flores Island in the Lesser Sundas, and the southern Bird’s Head and nearby Fakfak Peninsulas in Indonesian Papua. Deficits are forecast on New Guinea’s north coast and the nearby islands in the Bismarck Archipelago and Solomon Islands, provinces near the capital region in the Bird’s Tail Peninsula, and the western shore of the Gulf of Papua.

From December through February 2023, surpluses will shrink and downgrade considerably. Surpluses are forecast from Cambodia into Vietnam and Laos, and in southeastern Myanmar, the Visayas (Philippines), pockets in Sulawesi, the Lesser Sundas, Malukus, and Bird’s Head, Tail, and southern shore of New Guinea. Surpluses will begin to emerge in the Bismarck Archipelago and Solomon Islands as deficits recede. Moderate deficits are forecast in Sumatra, pockets in the Malay Peninsula and West Kalimantan, and northernmost areas of Laos and Vietnam.

The forecast for the final months – March through May 2023 – indicates widespread moderate to severe surpluses from eastern Cambodia through much of southern Vietnam. Exceptional deficits will emerge in southern Myanmar. Isolated small pockets of moderate deficit and moderate surplus are expected in the Philippines and Indonesia.

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

IMPACTS
The monsoon season continued in Southeast Asia and the Pacific, triggering flooding in many regions.

August flooding in Cambodia claimed nine lives and displaced 83,000 people. The worst-hit areas were Kandal, Takeo, Svay Rieng, Prey Veng, and Phnom Penh.

Parts of Thailand’s capital and largest city, Bangkok, were designated disaster areas after heavy rainfall produced flooding that covered roads, damaged farmland, and affected at least 20,000 people. Military vehicles were dispatched to help evacuate and deliver flood pumps, and the governor of Bangkok was seen knee-deep in floodwater pushing cars out of the flow. Some routes to the resort town of Pattaya were flooded and impassable, submerged in 30 centimeters (nearly a foot) of water, and officials warned residents to be on the alert for snakes seeking shelter.

August flooding and landslides in West Papua, Indonesia killed three people in Sarong City and damaged over 1,000 homes. In Sumatra, 35,000 people were affected in Bengkulu and North Sumatra Provinces.

Tropical Storm Ma-On (Florita) stuck the Philippines in late August, leaving three people dead as flooding and landslides were reported in many provinces, damaging roads, bridges, crops, homes, and power infrastructure.

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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