Concept of watershed

Watershed is a self-defended area, which does not allow any water from outside the catchment to enter into it and allow its excess water to discharge to a common point in a stream. The basic concept of watershed management is to conserve all the basic natural resources of the watershed and to plan for their optimal utilization, the approach and strategy are primarily based on the twin concepts of (i) integrated watershed management, and (ii) sustainable farming systems. A watershed consists of 3 physical sectors: (i) arable or cultivated lands, (ii) non-arable lands-village pastures and grazing ground, culturable wastelands and barren and uncultivable lands, and (iii) network of natural drainage lines. These sub-sectors are hydrologically interspersed. Watershed being a manageable hydrologic unit, conceptually and in practice, these subsectors should be treated as one geo-hydrological entity for project planning and implementation. Thus, sustainability of natural resources of land and water can be ensured. A watershed is defined as any spatial area from which rain or irrigation water is collected and drained through a common point. It is synonymous with a drainage basin or catchment area. Each watershed unit, however, is a well-defined topographically delineated area with a distinct boundary.

Role of watershed

The dry land or rainfed areas constitute 68% of the cultivable land (143.7million ha) contributing about 45% of the total foodgrains production in the country. It is estimated that at present around 45% of our food production is obtained from drylands and if estimated requirements are to be met, the productivity of drylands has to be increased by at least 72%. Hence, it is the need of the hour to develop suitable technology for increasing production of food, fibre and fuel to meet our increasing demands, since horizontal expansion of cultivable land is not possible, vertical increase in production is to be the only alternative. Watershed is a geographical unit that drains into a common point. Essentially, watershed-based natural resource development involves the optimum use of the watershed precipitation through improved water, soil and crop management and it is a complex long-term task and includes the integrated development of all types of lands – agricultural, grasslands, forest lands and uncultivated lands are integral part of the system.

India invested heavily in large-scale dams and irrigated agriculture. So much so, that currently, it leads the world in the development of irrigation facilities with an impressive record of engineering works. In 1995, there was a gross potential to irrigate over 80 million hectares. The availability of irrigation water has been a major factor for the success of the "Green Revolution;" it is therefore mainly confined to the irrigated lands. However, several concerns on the sustainability of irrigated agriculture have been raised. There was a slowdown in food production form irrigated agriculture due to smaller expansion of irrigated area and land fatigue. Many of the country’s irrigation development projects have been technically inadequate, economically unsatisfactory and environmentally disruptive. The actual performance of these projects has been far below their planned potential. The overuse of aquifers also threatens food supplies.

It suggests that in India, the Green Revolution-led growth in food production and the population increases have led to an unsustainable use of water. Nationwide withdrawals of groundwater are estimated to be double the rate of recharge and water tables are falling by one to three metres per year. The IWMI forecasts that as India’s aquifers get depleted, its grain harvest can fall by as much as one-fifth. The conservation of land and water resources in rainfed areas has been neglected for too long. The watershed was a hydrological land unit from where all the drain water emptied through one point. In other words, there was no specific physical limit for a watershed: it could vary from a few hectares to several thousand. This natural unit carved out through the interaction of rainwater with landmass and typically comprises arable and non-arable lands and natural drainage line.

The objectives of watershed developments are such as minimizing ecological degradation, reducing regional disparity and also opening up of greater opportunities for employment of the rural poor in the rainfed areas. The watershed framework thus provides the necessary inter-ecological linkages and is a logical unit for the integration of the sustainable use of land and water. It helps augment soil and groundwater resources. It also enjoins the biophysical, social and economic inputs, which if optimally managed, lead to diversified high agricultural production, control of environmental degradation and provide a mechanism for the recharge of groundwater aquifers. Watersheds thus ensure water adequacy to crops and reduce the risks of yield loss due to water related stresses.