Current General Studies Magazine: "General Studies - I (Geography Based Article)" August 2014

Current General Studies Magazine (August 2014)

General Studies - I (Geography Based Article)

The National Wetland Atlas 20111 (hereafter the Atlas) had the objective to map all types of wetlands and to become a national database by bringing out state-wise detailed publications. The Atlas, apart from producing the maps, estimated the area, vegetation and turbidity levels of wetlands. The Atlas project used satellite images from the Linear Imaging Self-scanning Sensors-m (liss-iii) with a resolution of 23 metres and thereby able to view water bodies up to a size of 529 square metres. The project was led by the Space Applications Centre (sac) of the Indian Space Research Organisation (isro), and 25 other specialist institutions undertook the project in their respective states.

Though the Atlas is an earnest effort to use the advancements in earth observation technologies such as the remote sensing and geographic information system (gis) tools, it is riddled with definitional problems, inconsistency of method and a poor understanding of Indian wetlands. The review highlights some of these issues affecting “man-made tanks and ponds”, which constitute the largest chunk of the Indian wetlands. The Ramsar Convention3 defines wetlands as “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres”.

This classification is simple, straight forward and has regional specificity. However, the Atlas used a three-level hierarchical classification without any regional specificity. Level 1 classified the wetlands as inland or coastal; Level 11 further divided them into natural or man-made; and Level m grouped all wetlands into 19 different classes.5 Since India is a land of continental proportions with substantial variations in its tracts, regional specificity is very important.

The purpose of the natural and man-made classification is to evoke an interest in and monitor these wetlands. India is known for developing water sources aimed at serving agriculture, fishery and other domestic and cultural uses. For example, man-made tanks offer many uses and services and every tank has some history. By way of their engineering and design, all tanks deliver water to the fields through gravity. Further, these man-made tanks are part of a large number of inland bird sanctuaries in south India, and are home to hundreds of species of fishes and plants. They have been functioning with little or no modification for centuries and seem to be “natural”. Unfortunately, even in India, many among the scientists are not aware of this fact. The researchers of this Atlas seem to be no exception. It appears from the methods used and the results arrived at that the study presumed that many hundreds of these ancient man-made systems were natural lakes.

The Atlas reports that India has an unbelievable number of 11,740 lakes that are natural, with a water spread constituting an area of 7.3 lakh ha. Since there is lack of basic appreciation of what is man-made and natural in this exercise, the purpose of classification has gotten defeated. Hence, the first level of classification may not be useful for explaining the role of humans in creating and sustaining the wetlands.

Further, the Atlas also suggests the existence of an additional classification called small wetlands (less than 2.25 ha) numbering around 5.6 lakhs with an estimated area of 5.6 lakh ha. It is not known whether these are treated as man-made or natural. In all probability many of these would be man-made, with a very few being natural.

Definitional problems and anomalies exist in defining lakes and ponds around the world, and across the disciplines dealing with the study of wetlands. However, in the Indian context, distinguishing lakes and tanks should not be an issue, Well-established documentation is available with the irrigation and revenue departments in many of these states. The Atlas defines natural lakes as “Larger bodies of standing water occupying distinct basins (Reid et al, 1976). These wetlands occur in natural depressions and normally fed by streams/ rivers”; and a man-made tank/pond as “an artificial pond, pool or lake formed by building a mud wall across the valley of a small stream to retain the monsoon (Margarate et al, 1974).” These definitions are inadequate and incomplete.

Lakes and tanks are both formed in naturally occurring depressions, but what differentiates them being natural or artificial is the ability to facilitate a gravity flow to receive and discharge water. Lakes and tanks might both have their defined basins. They also might be fed by rivers, streams and canals. But, the differentiation lies in how they are fed with water. Most of the naturally occurring lakes get water from the naturally formed channels, but all tanks get water from trained rivers or channels. Lakes may or may not have an embankment on their boundaries, but tanks certainly will have an embankment to divide the water spread with the command area. Many large tanks draw water directly from rivers as well. For example, Veeranam tank in Tamil Nadu draws water from the mighty river Cauvery directly through a channel that is partly man-made and partly natural, and the river Vaigai ends up in a large man-made tank called Ramanathapuram Big Tank, leaving a small stream of the river touching the Indian Ocean.