Drainage of ponded land through irrigation well in a leaky aquifer

Unsteady flow through an irrigation well installed in an inundated leaky aquifer underlying a semi-pervious soil layer has been analysed. Solutions for unsteady piezometric head distribution and rate of recharge into the aquifer under constant and variable surface ponding conditions have been developed for two cases, namely, flow from gravity well and constant rate injection well using approximate method of Laplace inversion technique [Schapery, R.A., 1961. Approximate methods of transform inversion for viscoelastic stress analysis. Proc. IV: US National Congress of Applied Mechanics, pp. 1075–1085]. The developed solutions for constant surface ponding condition have been verified with the field data at Tabageria village of Shaldahari watershed near Indian Institute of Technology, Kharagpur, West Bengal, India. The daily runoff depth, drainage depth and proceeding ponding depth have been analysed using solutions for variable surface ponding for Tabageria village in the monsoon year 1978. The Total volume and duration of water drained into aquifer through irrigation-cum-drainage well from a given command area of the watershed were computed. The analysis indicates that the gravity-cum-injection well is the best feasible solution for reclaiming surface impounding before sowing of winter season crop.