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Evaluation of drain spacing equations in the Indira Gandhi Canal command area, India

The aim of the study was to evaluate the drain spacing equations at Lunkarnsar farm in Bikaner District of Rajasthan, India. In subsurface drainage, field drains are used to maintain the water table and the salinity level in the root zone by draining excess water. The area was facing severe drainage problem and under waterlogged condition. The subsurface drainage system was installed at a spacing of 125 m with an average depth of 1.6 m below the soil surface at Lunkarnsar farm. The hydraulic head and drain spacing were determined by using four drain equations: Glover-Dumm, Van Schilfgaarde, integrated Hooghoudt and modified Glover equations. The percentage deviation between predicted drain spacing and actual spacing is −37.36% to −36.64%, 2.77% to 10.06%, 5.05% to 13.50% and −0.33% to 7.68% for Glover-Dumm, Van Schilfgaarde, integrated Hooghoudt and modified Glover drain equations, respectively. The modified Glover equation has shown minimum deviation from the actual value for drain spacing and hydraulic head. Thus, simple analytical approximation of the subsurface drain spacing for sandy soil texture was effectively applied in the evaluation of drain space.