Waterflow in the Paddy Field Installed with Sheetpipe Mole Drains

Abstract

Abstract Sheet-pipe is a sort of perforated mole drain placed horizontally between 30–50 cm below the land surface commonly having a water-logged problem. The sheet-pipe can be installed with a heavy machine mole drainer. The primary purpose of installing sheet-pipe is to maintain or control the expected water table in farmlands. Sheet-pipe having a diameter of 5 mm has been installed at a depth of 40 cm with a drain spacing of 4 m and length of 100 m covering a paddy field of 1 hectare located in Sukamandi District, Subang Regency, West Java, Indonesia. Field investigation and numerical studies were undertaken to figure out water head profiles surrounding the sheet-pipe. The paddy field installed with sheet-pipe can be drained faster (2 times), and in consequence, its water level can be managed easier. Right after an effective rainfall event (34 mm), the rainwater immediately infiltrates downward resulting in a parabolic curve of infiltration rate (maximum rate 0.94 cm/h) which differs with a standard infiltration curve (steady state 0.121 cm/h). Water level profile is horizontally flat except at the points closer to the sheet-pipe, which is showing the presence of outward gradients of the water head. The electrical conductivity was low (0.33 Ms/cm) due to the leaching effect.