COMPARISON OF AGRICULTURAL DRAINAGE DESIGN TECHNIQUES

Abstract

Drainage forms to be a crucial universal problem as about 70 percent of the irrigated global area is either affected with this problem or prone to it. In this study different available surface and subsurface drainage design techniques are compared using the data of KAL irrigation project command area located in West Coast Konkan region of Maharashtra State (India). Field data of rainfall, cropping pattern, soil characteristics and ground water table were used to compute various design parameters Iike runoff, drainage coefficient, and evapotranspiration etc. using appropriate methods, and surface and subsurface drainage systems designed for the study area. The time distribution method that computes runoff for design of surface drainage was more suitable for the study area than the rational and Curve Number (CN) methods. The runoff rate of 3.24 m3/sec computed from the time distribution method is recommended for use in design of surface drainage in the study area. The Manning's equation was found to be superior to regime theory for design of drainage channel, for it resulted into non-silting and non-erosive velocity of the flow through channel. The velocities of flow in channel design by regime theory were very low (0.30 to 0.39 m/sec), and therefore, these were not considered for the study area. For subsurface drainage design, the drainage coefficient of 0.60 cm/day computed by USDA empirical formula was appropriate compared to 0.28 cm/day by the Netherlands equation. For design of drain spacing in surface drainage, the Hooghoudt's equation. computed the highest drain spacing of 51 m from the Hooghoudt equation was adopted..