Current General Studies Magazine: "Geographical Based Article" September 2014

Current General Studies Magazine (September 2014)

Geographical Based Article

Lakes, Tanks and Ponds

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.

It is very unfortunate that such confusion in basic classification happened in the southern states that have a long history of documenting the tanks. Based on this incomplete understanding, the Atlas reports Tamil Nadu as having 4,369 “natural lakes” with a wetland water-spread area of 3.16 lakh ha. This amounts to more than a quarter of all wetlands in the state. However, Tamil Nadu is known to have not more than a handful of natural lakes.

The Atlas also reports Karnataka as having 27 natural lakes and Andhra Pradesh as having seven. This again tends to show that whatever was the definition that they adopted, it was not followed consistently across these three states, which have similar topography and wetland systems. It could also be the case with other Indian states in central and eastern areas, and needs to be verified. The existing definitions and classifications that are widely used by the irrigation and revenue departments would have helped the exercise provide its results in a meaningful manner.