EVALUATION OF SUBSURFACE DRAINAGE SYSTEM IN ISLAMPUR PILOT PROJECT AREA UNDER UPPER KRISHNA PROJECT COMMAND

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Date
2001-08-13
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
A study was conducted to evaluate the subsurface pipe drainage system that has been installed during 1991-'96 at Islampur village, Gulbarga district in Upper Krishna Project Command area by the University of Agricultural Sciences, Dharwad with the funding by the UK? CADA (Command Area Development Authority). The subsurface drains were executed in 26 ha of black soil (Vertisol) area using the spacings of 20, 30, 40 and 60 m along with shallow open drains. The brief results of the present study undertaken during 1997-'98 are presented below. The weighted average discharge of the subsurface drainage system were 7.0 and 6.9 m/d during kharif and rabi/summer respectively. The overall weighted average discharge of project area was 6.9 m/d which was nearly 3.5 times that of the design drainage coefficient (DC). The spacing and the drainage materials had influence on drain discharge; generally, the discharge was inversely related to the spacing and the PVC perforated corrugated pipe with nylon filter combination was found to be best of the lot among the drainage materials. The PVC perforated corrugated pipes without any filter also was found to work satisfactorily. However, this needs to be tried in few more areas for confirmation and large scale adoption. The average hydraulic conductivity by the auger hole method was 0.096 m/d whereas the areal hydraulic conductivity by the drain outflow method was 0.351 m/d which was eight times higher than that obtained by the earlier method. The EC and ESP decreased with soil depth for all the spacings before sowing and vice-versa after harvest of the crop. The ESPwas directly related to the drain spacing as the values increased with spacing for both the cases of before sowing and after harvest of the crop. However, the ESP values were slightly higher at deeper layers after harvest of the crop. The leachate (drain water) salinity decreased gradually from July 1997 to till March 1998 both in the laterals and the outlets of the mains indicating that the salts accumulated in summer months were leached during the period. The quality of leachate was found to be good and fit for reuse as irrigation water without any salinity and sodicity hazards as SAR, EC, pH, RSC and SSP were below the critical limits. The irrigation to various crops was found to have local influence on drain discharge. Similarly, the results indicated the effect of rainfall on increase in drain discharge. The cropping intensity in the study area increased (161.95%) and was more than 2 times that before the drainage system. There was significant increase in the productivity of crops after the drainage installation over the predrainage yield levels. Though paddy is a banned crop, its area is increasing at alarming rate which needs to be checked to minimise the problems of waterlogging and salinity.
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