. .



Land, water resources and glaciers

Our land resource is subjected to a great threat from salinity and waterlogging

Dr. S.M. ALAM, Dr. R. ANSARI and M.A. KHAN
Nuclear Institute of Agriculture, Tandojam
Nov 27 - Dec 03, 2000

The land resources of Pakistan and their use have a great impact on economy. Only 26% of Pakistan's land is used for agricultural purposes, about 4% is used by the government for forestry, and 12% is culturable waste.

Land resources of Pakistan
Area ( Mha )

Geographic area

79.61

Reported area

58.00

Cultivated area

21.69

Irrigated area

16.50

Rainfed area

4.75

Forest land

4.06

Not available for Cultivation

Culturable waste

8.51

Water deficits and salinity: The two central dilemmas facing agriculture in Pakistan are limited amounts of water for irrigation, and increased salinity. The water budget shows that of the 135 million acre feet of water which flows annually in Pakistan's rivers, only 12 million acre feet reach the farmer's fields. This figure is supplemented by a further 14 million acre feet of effective rainfall, and 45 million acre feet from tubewells. Leakage of canals and inappropriate irrigation practices have resulted in large increase in water-tables in many areas of Pakistan. As a result of this, the Indus plain now has 6.3 million hectares of salt affected land. Both salinity and waterlogging are the twin menace for the agricultural productivity of the country.

Salt affected lands in Pakistan ( Mha )

Province

Area
Cultivated

Saline

Saline-sodic

Sodic

Total saline
/sodic

. . .

Perm-
eable

Imper-
meable

. .

Punjab

11.85

0.504

1.225

0.856

-

2.586

% salinity

21.82

19.5

47.4

33.1

-

100.00

Sindh

5.40

1.342

0.673

0.277

0.028

2.321

% salinity

42.43

57.8

29.0

12.0

1.2

100.00

NWFP

1.89

0.502

0.005

0.009

-

0.516

% salinity

27.30

97.2

1.0

1.8

-

100.00

Balochistan

1.48

0.175

0.125

0.004

-

0.304

% salinity

20.54

57.7

41.1

1.4

-

100.00

Pakistan

20.69

2.523

2.028

1.148

0.028

5.728

% salinity

27.68

44.1

35.4

20.0

0.5

100.00

The area under water logging ( 0.3 meter ) is about 54% of the total surveyed area.

 


 

Extent of Waterlogging in Indus Basin.
Water logged area ( m.ha).

Province

Area surveyed

0-1.5 m

1.5-3 m

Total water logged

% of surveyed areas

Punjab

9.964

0.998

3.1888

4.184

41.0

Sindh

5.852

1.061

3.405

4.464

76.3

NWFP

0.538

0.043

0.140

0.183

34.0

Balochistan

0.036

0.005

0.031

0.036

100.0

Pakistan

16.390

2.115

6.764

8.869

54.1

The magnitude of the problem can be guaged from the fact that the area of productive lands was being damaged by salinity at a rate of about 40,000 ha/year at one stage. However, according to WAPDA authorities, it has not only been checked but also reversed and at present the reclamation rate is 80,000 ha per annum. On one hand, our land resource is subjected to a great threat from salinity and waterlogging, while on the other, our population is increasing at a very fast rate of 3.1% per annum. It is expected that our population will grow to 148.1 million in the year 2000 and we shall need at least 40-80% more wheat, edible oil, sugar, milk and wood products at the present rate of consumption.

Water budget for Indus Basin
( million acre feet )

Average annual flow in rivers

145

Flows to Arabian sea

35

Diversion into irrigation system

110

Losses from irrigation system

98

Conveyance losses

28

Delivery losses

51

Field application losses

19

Net available water for irrigation

12

Water pumped from tubewells

45

Effective rainfall

14

Net water available for use by crops

71

Availability of water through efficient water management is the main right path for crop production. The Indus basin irrigation system encompasses the Indus river and its three major water storage reservoirs, 19 barrages/headworks, 12 link canals, and 43 canal commands covering about 90,000 villages/chaks. It covers about 39,000 miles. The three major reservoirs, Mangla, Tarbela and Chashma were built by Pakistan on signing the World Bank sponsored Indus water basin treaty between India and Pakistan. Irrigation in this country, depends on both surface and underground water resources. The quantum of water entering the rivers aggregates to about 145 million acres feet per year. Of this about 110 million acre feet is transferred to canals for irrigation annually (72 per cent) and remaining 35 million acre feet flows down into the sea because of lack of storing facilities. The quantum of water entering irrigation water courses from the canals amounts to 98 million acre feet per annum. Water obtained from 480,000 public and private tubewells for irrigation purposes has been estimated at 45 million acre feet annually. Thus, the total quantum of water entering the water courses both from canals and tubewells aggregates to 122 million acre feet annually. Of the 145 million acre feet water entering the canals each year, about 28 million acre feet (i.e. one fourth) is lost in transit due to a number of factors. Besides, about 40 million acre feet (i.e. 40 per cent lost within the water courses themselves). Thus, only 73 million acre feet water reaches the field. Also, about 18 million acre feet water is wasted in the fields. Taking into account all the losses as indicated above, only 55 MAF water is normally left for the irrigation of crops. While, 90 MAF water annually goes waste. Thus, the wastage comes to about 62 per cent. The farmers normally need 3.5 MAF water per acre for cultivation, our crops get only 1.5 MAF water per acre.

Projected population and requirement of different Agricultural commodities

Year

Population

 

      Requirements
   

wheat

oil edible

sugar

milk Wood product
 

Million

( m.tons )

   

m.cu.meters

1947

31.3

4.6

0.27

0.30

3.01

28.80

1985

94.7

13.0

1.17

1.20

9.11

85.65

2000

148.1

20.2

1.83

1.67

14.25

189.57

Water is the earth's most distinctive constituent and is an essential ingredient of all life. Its deficit is one of the most common environmental factors limit crop productivity. Most of the water in the hydrosphere is salty and much of the fresh water is frozen. It has been estimated that oceans all over the world contain about 97% of the planet's water, seven continent of about 2.8%, and the atmosphere about 0.001%. Similarly, about 77% of the associated with land is found in ice caps and glaciers and about 22% is found in ground waters, much of which is uneconomical to retrieve. This scenario leaves only percentage of readily manageable fresh water as a resource of the water supply for the population. Plants transpire about 100-300 times more water during the assimilation of CO2 than is required for their growth and the production of a usable yield. It has been estimated that 600 kg of water is transpired to produce 1 kg of dry maize, and to produce 1 kg dry biomass, normally 225 kg of water is transpired. It was further reported that to produce 1 kg of sucrose, sugar beet plants transpire 465 kg of water, and to produce 1 kg dried biomass, they transpire 230 kg water. The world's land surface occupies about 13.2x109 ha, of which 7 x 109 ha is arable; only 1.5 x 109 ha of which is cultivated land. The cultivated lands, about 0.3 x 109 ha (23%) is saline and another 0.56 x 109 ha (37%) is sodic. Although, the data are tenuous, it has been estimated that one-half of all irrigated lands (about 2.5 x 108 ha) are seriously affected by salinity or waterlogging.

The northern regions of Pakistan is full of world's largest glaciers. They are almost at the height of 4720 meters above the sea level. They form the biggest function of glaciers on earth giving birth to a pool of snow lake, in the surrounding of mountains. The Himalayas, the Karakorams the Hindu Kush and the Pamirs in the north of Pakistan gave birth to the thickness of and the most amazing duster of the highest peaks and largest glaciers in the world away from the Polar regions. The valleys of mighty Karakorams to the west of Himalayas is more than 1500 square miles. About 37 per cent of the surface area of Karakoram is under glaciers as compared to 17 per cent of the Himalayas in Nepal, India and China put together and 22 per cent of the European Alps. There are also about 3000 small glaciers and tributaries. The hundred miles of cool, rush, splashing and scintillating winnowing torrents gushing out of the shorts of these glaciers mingle together to form about 3180 kilometers long Indus river, which flows the plains of Pakistan into Arabian sea near Karachi. Some of the important glaciers located in the mountainous regions of Pakistan are mentioned below:

 

Name of some important glaciers of Pakistan

Name

Area covered in square kilometers

length in kilometers

Siachin

685

71

Baltoro

529

62

Biafo

383

65

Hispar

343

49

Panmah

258

42

Chorgo lugma

238

44

Batura

220

56

Khurdoin and Yukshin

135

37

Braldu

123

36

Barpu

123

33

Yaqlil

114

31

Virjerab

112

38

Mohmil

68

26

Gasherbrum

67

25

Malanguthi

53

22

All these glaciers are the sources of water, which after melting in the summer season enters into river Indus, travelling distances of about 1800 miles and finally enters into Arabian sea near Karachi.