Effect of head loss to envelope material on drain performance

The study was conducted at Central Soil Salinity Research Institute, on pre-installed subsurface drainage system at Mundlana in Sonepat district to determine the head loss due to envelope materials around the drain. The observed hydraulic head varied inversely with time since operation of drainage system but directly with the distance from the tile drain centre. The loss of head due to envelop materials, h (E) is normally considered negligible but in reality envelope materials also cause loss of head. At E(K), the expected value of hydraulic conductivity of 0.80 m/day, consideration of h (E) of 40 cm represented actual water table recession under field condition. The accuracy of predicted) hydraulic heads, from numerical solution of Bossinesq equation, in representing actual water table recession increased directly with the increase in head losses due to envelope materials.