General Characteristics of Regions

The north mountain and midland region is not prone to droughts. Only moderate droughts occur at some places in this region. Droughts rarely occur for consecutive years, except the droughts that occurred during the summer season of 1988 and 1989. The northeast part of this region is more prone to drought than the rest of the region. The Red River delta is relatively more drought prone, and severe droughts occurred there in 1960, 1961, 1963, and 1964.

The north-central region is a narrow belt of land by the East Sea and is covered with many forests and mountains. The geographical area of this region is about 5.1 millions ha, with nearly 1.3 millions ha being used for

Table 27.1 Regional distribution of harvested area and production of rice and maize crops in Vietnam for 1999

Agricultural

Harvested area (1000 ha)

Production (1000 tons)

Table 27.1 Regional distribution of harvested area and production of rice and maize crops in Vietnam for 1999

Agricultural

Harvested area (1000 ha)

Production (1000 tons)

Region

(1000 ha)

Rice

Maize

Rice

Maize

North mountain and midland

4467

669

267

2291

551

Red River delta

1479

1203

103

6354

319

North-central

5150

678

88

2653

202

South-central

4422

544

43

2236

95

Southeast

2339

390

91

1151

298

Central highland

5441

166

73

403

261

Mekong River delta

3987

3965

22

16549

50

agricultural production. This region is influenced by the eastern hot and dry winds (Laos wind) and is very hot during the dry season.

The south-central region runs along the coastline, and many streams and rivers that originate from the Truongson Mountain Range flow in this region. The geographical area of this region is about 4.4 million ha, with 640,000 ha being used for agricultural production. About 65% of the agricultural area is irrigated. Most of the population of this region (about 7 million) is engaged in agriculture or forest-related activities. During 195898, droughts occurred in this region during the summer season of 1962, 1969,1993, and 1998. Relatively severe droughts occurred during winterspring seasons of 1970 and 1984. In general, moderate and severe droughts occur in this region during the summer season.

The central highland region (Taynguyen plateau) is a mountainous plateau with average height ranging from 500 to 800 m above mean sea level. Its geographical area is 5.5 million ha, of which 112,000 ha is arable and very fertile. More than half a million hectares is hilly and is planted with commercial crops, such as coffee, tea, pepper, and fruits. Before 1980, droughts rarely occurred in consecutive seasons in this region, but since 1980, there have been cases of moderate droughts occurring for consecutive seasons.

The southeast region is an old alluvium area with a geographic area of 2.4 million ha, out of which 1.3 million ha is used for agriculture, 0.6 million ha for forestry, and about 1 million ha for commercial crops.

The Mekong River delta is the biggest rice basket of Vietnam. Its geographical area is about 4 million ha, including 2 million ha of rice and subsidiary areas. The vast majority of population of this region (16 million) lives on rice and fish production. The Tien and Hau rivers are the major irrigation sources. Water is transported to rice fields via a condensed canal network. The annual harvested area of rice is more than 1.26 million during the winter-spring season, 1.34 million ha during the summer-autumn season, and more than 0.5 million ha during other irregular periods. The

Table 27.2 Rice area (in 100 ha) lost due to droughts that occurred in different seasons and regions of Vietnam during 1980-98

North mountain and midland Red River delta North-central South-central Mekong River delta

Table 27.2 Rice area (in 100 ha) lost due to droughts that occurred in different seasons and regions of Vietnam during 1980-98

North mountain and midland Red River delta North-central South-central Mekong River delta

Winter-

Winter-

Winter-

Summer-

Winter-

Summer-

Winter-

Summer-

Year

spring

Summer

spring

Summer

spring

autumn

Summer

spring

autumn

Summer

spring

autumn

Summer

1980

945

75

30

5

7

417

279

1981

379

81

850

13

731

1713

585

461

150

11,054

4042

1982

410

48

542

1200

2342

2440

571

150

1305

1983

213

194

35

15

660

2464

6

1615

2060

1372

38,162

1984

690

71

470

615

659

1709

30

1998

11

200

2011

4693

1985

821

245

40

5

592

1386

2700

685

3385

4600

1986

200

25

1065

562

716

124

150

6300

109

1987

530

90

1995

1060

610

1437

1270

21,427

8357

1988

1542

2961

2036

162

680

1901

2452

450

6877

640

1989

783

112

25

12

598

162

88

5235

8340

280

1990

1542

1835

644

1200

294

105

10

277

314

524

18,103

631

1991

1676

9047

1035

685

1814

2173

264

15

257

15

50

21

1992

1538

1115

1545

620

1143

1988

3000

5

326

111

1250

39,062

7835

1993

1086

1196

752

4

2138

12,305

5500

15417

1834

7045

3180

8564

188

1994

1100

763

24

174

1222

1234

8

616

1223

771

4886

1074

1995

989

977

724

190

509

4092

2500

169

239

295

573

777

89

1996

2735

609

12

155

2815

2350

696

969

735

2735

527

1997

796

152

5

17

750

300

24

352

1067

111

14,217

1998

1507

858

160

31,018

12,900

758

5797

657

19,414

32,109

1999

19,482

20,454

11,282

6184

9658

62,650

37,683

16,449

23,995

16,451

32,343

182,524

71,248

weather in the Mekong River delta is moderately warm most of the year. Therefore rice can be cultivated at various times during the year, provided sufficient irrigation is available. In this region, severe drought occurred during April-June of 1983, 1992, and 1998, and during October-December of 1958 and 1992 (Bui, 2000).

Probability of Agricultural Drought

Table 27.3 presents the probability of monthly droughts in different regions of Vietnam. In general, probabilities are high during January-April, moderate during October-December, and low during June-September, except in north and south-central regions where drought probabilities are higher than other regions. In addition, drought probabilities are higher for southern regions than for northern regions.

In addition to monthly drought, studying dekadal (10-day) dry periods is important for better monitoring of crop conditions. If rainfall during a dekad is less than 30 mm, a dekadal dry period is considered to have occurred. Probability of dekadal dry periods was computed using a method proposed by Frere and Popov (1982). The probability distributions of second and third dekad dry periods for some major weather stations are shown in figure 27.2 (Nguyen, 1998, 2000, 2001).

Was this article helpful?

0 0

Post a comment