Southeast Asia & the Pacific: Water deficits in Cambodia to abate after April

28 February 2018

THE BIG PICTURE
The 12-month map (below) indicates water surplus of varying intensity in western Myanmar, Laos, much of Vietnam, southern Thailand, Philippines, Brunei, and scattered pockets in Indonesia.

Severe water deficit is forecast for western Cambodia, central and southern Sumatra, a small pocket in western Malaysian Borneo, and south-central Papua New Guinea.

Mild deficits are expected in Thailand and pockets of Myanmar.

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

In the near-term forecast through April Cambodia continues to stand out with exceptional water deficit in the west. Moderate to extreme deficits are expected to emerge in central and southern Sumatra and Java, and milder deficits in western Borneo. Deficits around the Gulf of Papua in Papua New Guinea will intensify, reaching exceptional severity, while deficits farther north and in the central Highlands retreat.

Surplus conditions are expected to remain intense in western and eastern Myanmar, northern Laos, along the Mekong River until it reaches Cambodia, and central Philippines. Surpluses of varying intensity are forecast for much of Vietnam, pockets of Thailand, Brunei and northeastern Borneo, and isolated pockets in Indonesia.

From May through July surpluses will retreat considerably, leaving primarily moderate conditions in northern Vietnam, Philippines, and scattered pockets in New Guinea and nearby islands. Notably, Cambodia will transition away from long-term exceptional water deficits in the west to near-normal conditions. Moderate to severe deficits will emerge in much of Malaysia, and will continue to emerge in Sumatra, but will shrink in Java. Deficits of lesser severity will continue to emerge nearby in western Borneo. Some primarily mild deficits will begin to emerge in Southeast Asia.

After July, moderate deficits are forecast throughout Southeast Asia with more severe deficits in the southern Malay Peninsula, Sumatra, and Timor-Leste. Scattered surpluses are forecast for the remainder of Indonesia and for New Guinea.

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

IMPACTS
Heavy downpours hit the Malay Archipelago in early February, causing flooding, landslides, and evacuations across the region. Officials evacuated 6,500 Indonesians from Jakarta, where floodwaters reached 2 meters (6.6 feet) in some areas, and landslides in satellite cities killed at least three people. In the Malaysian state of Sarawak, 5,500 people were evacuated to 31 temporary relief centers, and 55 schools were closed as firemen carried schoolchildren to safety. In Brunei, several floods and landslides inundated shops and residences, and choked roadways.

The Malaysian government has launched a RM572 million (US $147 million) river basin development project which includes a flood mitigation plan for the northern state of Kelantan. Kelantan is vulnerable to flooding during the monsoon season from October to January. The project is intended to relieve 100,000 state residents of some effects of monsoon flooding by dredging the mouth of the Kelantan River, and constructing flood walls and control doors.

In late January, heavy rainfall in Bangkok, Thailand caused flooding and halted traffic in the metropolis of 8 million. The city has not yet completed construction of five planned underground "water banks" to help alleviate chronic flooding, with official assurances that three will be completed by the onset of the rainy season and the remainder by the end of the year. With a combined holding capacity of 27,030 cubic meters of water, the banks were designed to accommodate excessive precipitation formerly absorbed by natural aquifers that have since been rendered useless by non-permeable surfaces such as pavement.

In a related project costing 273.6 million baht (US$8.7 million), Bangkok will also move ahead on development of five rainwater retention ponds with a combined capacity of 141,100 cubic meters.

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