Drought and unusually high temperatures are now pervasive throughout Vietnam. A senior expert told Tuoi Tre that the proximate cause is El Ninõ.

Canals and streams are drying up. n the photo, Kenh Cha Va (Soc Trang 0)

The rainy season ended very early last year. There was little rain at the end of July and from August onward, hardly any at all. The midsummer downpours (mÆ°a ngâu) just didn’t happen. On top of that, El Ninõ’s influence continues to be strongly felt. The average temperature in recent months has been considerably higher than average. In the north, the winter cold waves have also been unusual. Typically there are four or five cold spells each month of roughly equal intensity and duration, but not this year.

There have been as many cold spells as usual, three or four each month, but their intensity and duration have been irregular. Some have been quite sharp, with prolonged chill, but between these, there haven’t been less intense cold waves, but instead extended periods of warm weather – in particular the eleven day warm spell before Tet, something extremely rare in the north of Vietnam according to the annals, and never seen since systematic weather measurements began.

That hot spell lifted the temperature in Hanoi to 7ºC above normal; the lowest reading all month was 21ºC though the average temperature in February is 17.5-18 degrees! After that, there was a cold spell that persisted all through the Tet holiday. Then came another warm spell, 2-3ºC above normal. The sudden shifts, especially, make everyone sense that the weather’s become odd. February 2009 was hot, too; the temperature averaged 4-5 ºC above normal. That year, however, the changes were gradual, so no one thought it odd.

Then there is the extraordinary drought. Water levels in the northern rivers have fallen way below forecasts. At the place where the depth of the Red River is charted in Hanoi, it has fallen through the previous low, 70 centimeters, to almost dry — a wholly unimagined low of ten centimeters!

The base temperature for the last three months is also the highest recorded in our era, and that high level is typical of El Ninõ cycles. 1997-98 was also an El Ninõ period, and the temperature was elevated then too.

Tuoi Tre: This year, the entire country is suffering from drought. Besides lack of rain, are there other causes?

Le Thanh Hai: Rain’s not scarce just in Vietnam; all of Southeast Asia and southern China are suffering. In Laos and Thailand, the flow in the Mekong is at an historic low. The rainy season usually lasts through October, but by October last year, it had ended all throughout mainland Southeast Asia. Because rainfall was inadequate, the hydropower plants made extra effort to store up water behind the dams. When they produce power, water is released from the dams but not enough to restore the flow in the rivers to normal levels.

Tuoi Tre: What’s your view of the salt water infiltration situation in the south?

The condition of the Mekong river is will improve only slowly, so the outlook is less optimistic than in the north. The salt water infiltration in the Delta provinces won’t subside until the rains start. We’re seeing salt water infiltration up to 40 kilometers inland, and it could penetrate even further up to the first part of April.

Tuoi Tre: With all these changes, should we expect this summer to be as hot as last summer?

Hai: What we can see most clearly is that this March and April will average one or two degrees hotter than normal, and there may be some really hot spells, more like summertime. Rainfall will be twenty to fifty percent below normal – and these are the dryest months of the year in the Central Highlands and the south. Possibly there will be a few unseasonable showers in April there, but not enough to relieve the drought conditions. [Typically the southwest monsoon does not begin until mid-May – ed.] In the north, we hope some heavy rains and thunderstorms at the end of March will break the drought. And if El Ninõ returns to normal, as is forecast now, then it isn’t certain that this summer will be hotter than average.