Two sides of a canal

Indira Gandhi Canal's salubrious effect on the Thar has been overlooked

The Indira Gandhi Canal, also called the Rajasthan canal, which ferries water from the Harike Barrage in Punjab to the distant Thar Desert in Rajasthan, has been much maligned for its adverse environmental consequences, especially waterlogging of areas around it. What has escaped notice is the salubrious effect of the canal water-based intensive farming on the inherently barren desert soil. A recent comprehensive study of the changes in the soil properties indicates that irrigated agriculture has propped up the carbon content of the soils and improved their overall physical and chemical health. The study report, in fact, commends irrigated farming as a management option for restraining desertification in the Thar and other similar deserts in the hot tropical regions.

This is a significant policy suggestion given that the sprawling Thar desert spans some 2,00,000 sq km in Rajasthan and its adjoining states. A typical feature that sets the Thar apart from the world's other great deserts is the exceptionally large population of humans and livestock that it has to support, notwithstanding its innately low carrying capacity. The average population density in this arid belt is 84 to 90 people per sq km, against just three to six people in other deserts. The livestock count, which constitute the mainstay of the livelihood of people here, too, is very high and is growing rapidly. This is adversely affecting the grazing lands and local vegetation which, in any case, are sparse. The rainfall in the Thar Desert is extremely low and sporadic. On an average, there are just 16 rainy days in a year.

Much of the land in the desert has traditionally been covered with sands and sand dunes, some of which even tended to shift from one locale to another. Many of these dunes have since been stabilised or leveled to facilitate farming in the canal command areas. It is true that waterlogging had occurred on quite a substantial scale, especially in the initial stages of the expansion of the canal network, but that was largely because adequate stress was not simultaneously laid on provision of proper drainage. This issue has since been addressed to a considerable extent, mitigating the waterlogging menace.

On the upside, the irrigation, and also the cotton and wheat-based cropping systems that have sprung up in the canal command area due to availability of water, have had several positive effects on the sandy and loamy desert soils. These have been quantified and documented in this study carried out by an inter-institutional group of scientists led by S K Singh of the Kolkata-based regional centre of the National Bureau of Soil Survey and Land Use Planning.

The report maintains that irrigation and regular cropping have led to a perceptible improvement in the physical, chemical and biological characteristics of the soils in the Thar Desert, enhancing their water holding capacity and augmenting their fertility. This qualitative upswing is attributed partly to the sediments (clay and silt) brought in by the canal that are rich in nitrogen, phosphorus, potassium and carbon components, and partly to the addition of organic matter (manures) to the soil as part of the routine agronomic practices for crop cultivation. The presence of microbes in the soils, which is critical for its long-term health, too, has tended to look up due to increase in its organic carbon content. In the past 47 years, canal water irrigation has helped push up the silt content of the soils by 7.2 per cent and clay content by 5.4 per cent even while simultaneously reducing the proportion of sand by 12.5 per cent. Besides, it has moderated soil temperature in both summers and winters to create better ambience for the growth of roots and micro-organisms.

"These observations suggest that irrigation and cropping sequences together may be one of the management options for greater sequestration of organic carbon to improve physical and chemical conditions of the soil and reduce desertification in the Thar desert," the report concludes. This unambiguous inference should serve as an eye-opener for the anti-water development lobby that has been resisting construction of dams and other projects for conveying water to water-stressed areas to irrigate crops and meet drinking water and other needs of people.

surinder.sud@gmail.com