Historical underpinnings

Rapid growth in groundwater use is a central aspect of the world's water story, especially since 1950. Shallow wells and muscle-driven lifting devices have been in vogue in many parts of the world for millennia. In British India (which includes India, Pakistan and Bangladesh), these accounted for over 30% of irrigated land even in 1903 (http://dsal.uchicago.edu/statistics/1894_excel) when only 14% of cropped area was irrigated. With the rise of the tube well technology and modern pumps, groundwater use soared to previously unthinkable levels after 1950; as a result, by the mid-1990s, groundwater-irrigated areas in

Aquifer systems

Explanations

Yield potential (LPS)

Alluvium, extensive

>40

Alluvium and sandstones, discont.

10-40

Limestones

5-25

Crystalline rocks

1-40

Basalts

1-25

Aquifers in hilly areas

<1

Fig. 2.4. Major aquifer systems of India. (From CGWB, 1995, p. 145.)

30,000

25,000

30,000

25,000

Fig. 2.5. Groundwater-irrigated area in countries with intensive groundwater use in agriculture. (From Food and Agricultural Organization, 2003.)

CT

CO

TO

c

£

o

'c

TO

M

<c

£

1—

<D

N

o

D

(f)

CO CO CO o

Fig. 2.5. Groundwater-irrigated area in countries with intensive groundwater use in agriculture. (From Food and Agricultural Organization, 2003.)

India, Pakistan and Bangladesh together were much larger than anywhere else in the world (Fig. 2.5). Indeed, one might surmise that of the 270-300 million hectares of global irrigation economy, more than one-third - around 110 million hectares - likely comprises groundwater-irrigated areas in the Indian subcontinent alone. Other groundwater economies of the world seem small by South Asian standards. In Spain, groundwater use increased from 2 km3/year in 1960 to 6 km3/year in 2000 before it stabilized (Martinez-Cortina and Hernandez-Mora, 2003). In western USA, which is larger in geographic area than the Indian subcontinent, although growth in total agricultural water use has tapered off, groundwater's share in irrigation has increased from 23% in 1950 to 42% in 2000, and has stabilized at around 107 km3 (http://water.usgs.gov/pubs/ circ/2004/circ1268/). In the Indian subcontinent, groundwater use soared from around 10-12 km3 before 1950 to 240-260 km3 in 2000 (Shah, 2005). Despite its growing pre-eminence, data on groundwater use are hard to find; however, Fig. 2.6 uses patchy data available from several countries to backcast the probable trajectories of growth in groundwater use in selected countries. While in the USA, Spain, Mexico, and African countries like Morocco and Tunisia total groundwater use peaked during the 1980s, in South Asia and the North China Plain, the upward trend began during the 1970s and is still growing (see Wang et a/., Chapter 3, this volume).

The striking aspect of South Asia's (and China's) groundwater boom is that it has acquired its present prominence only after 1970. Figure 2.7 shows the growth in the number of irrigation pumps in India during 1951-1993 and projects these to 2005. Figure 2.8 shows the corresponding change in the relative

CO CD

^200

B 150

13 S

1 100

B 150

13 S

1 100

1940

1950

1960

1970

1980

1990

2000

2010

1940

1950

1960

1970

West Europe Spain Mexico China

1980

India Pakistan Bangladesh Sri Lanka

1990

2000

2010

Vietnam Ghana South Africa Tunisia

Fig. 2.6. Growth in groundwater use in selected countries. (From authors' estimates.)

Fig. 2.6. Growth in groundwater use in selected countries. (From authors' estimates.)

<> Oil engines

Electric pumps

Total irrigation pumps

- Polynomial (total irrigation pumps)

Fig. 2.7. Growth of irrigation pumps in India. (From World Bank and Ministry of Water Resources, 1998.)

' Surface water --Polynomial (net irrigated area)

Groundwater Net irrigated area

Polynomial (groundwater) Polynomial (surface water)

Fig. 2.8. Changing share of different sources in India's irrigated area: 1951-1998-2020.

' Surface water --Polynomial (net irrigated area)

Groundwater Net irrigated area

Polynomial (groundwater) Polynomial (surface water)

Fig. 2.8. Changing share of different sources in India's irrigated area: 1951-1998-2020.

share of different sources of irrigation in total irrigated area in India, indicating clearly that groundwater wells that irrigated just around 10 million hectares in 1970 are now serving over 35 million hectares of net irrigated area in India. Surface irrigation sources - tanks and canals - that had dominated irrigated agriculture in India for decades now gave way to groundwater irrigation. How did this role reversal affect the economics of South Asian agriculture?

0 0

Post a comment