Ground water recharge techniques for the Deccan Trap Aquifer formations

The Deccan Trap terrain covers an area of about 200,000 sq. miles in Peninsular India. The geomorphological features of the terrain provide fewer number of sites for the surface storage of water, like dams, tanks etc. Hence most of the farm-lands of this terrain have to depend upon rains and ground water in trap rocks for their irrigation needs. The Trap rocks are not only poor producers of water but also have lesser water holding capacities when compared to the sand and gravel beds. The latter problem is further accentuated by their near horizontal dips and steeply eroded hill stopes. Wherever lateral truncation of the Trap flows due to crosion occur, ground water from these flows seeps out through the sides of their slopes into the gullies, streams and rivers, due to reduction in the length of path of movement of ground waters. The flows get drained so fast, that by summer, water tables recede faster and go deeper, thereby wells become useless for irrigation purposes. Thus, vast areas of the Trap terrain remain barren during summer months and are exposed to wind erosion. The rate at which the water levels of wells starts falling down along with the variations in quantity and distribution of rain fall make irrigation a problem even during winter months, especially for the high yielding varieties of crops. In order to solve this problem, water levels of wells have been measured prior to the construction of contour bunds in Nariaoli Mechanised farm near Nariaoli village, Sagar district, as an experimental measure, for which detailed soil and ground surveys were made. On the basis of soil characteristics of the land, the contour bunds are located in such a manner that the pools formed behind them acted as recharge areas. In addition, check dams across the nallahs are constructed such that some of the reservoirs, situated in the influent parts of the stream courses acted as recharge basins, while those situated in the effluent parts of the streams served to check the free flow of ground water into the streams. On this principle pratically all the villages around Sagar have been bunded, though not all the streams check-dammed. Sets of water table maps were prepared, once before the onset of rains and the second time immediately after the rains. As a result of these recharge methods, each dug well is now capable of irrigating eight to sixteen times more acreage during winter and two to four times more acreage during summer than what each well was capable of before. Streams, that were ephemeral, have become seasonal, and seasonal streams have become nearly perennial. The authors, therefore, conclude that vast areas of low ground farm-lands of the Trap terrains can be provided with adequate irrigation facilities even during summer months with the help of soil and water conservation practices. This may go a long way to meet the demands for food by the ever growing population of India, as the major part of Deccan Trap terrain involved is endowed with rich soils.