The Distirbution of Tensiometric Moisture Potential in Relation toSeasonal Rainfalls for a Tile Drained Clayey Soil

The objective of this study was to investigate the effectiveness of tile drainage system, tile flow rates in relation tosoil matric potential ranges and water table levels based on seasonal rainfalls in a heavy clayey alluvial soil profile. In order to observe water potential, drain flows, water table levels, climatic parameters, Gardner’s field type irrometers/ tensiometers, a weather station, digital water flow meters, automated moisture probes, and piezometers were established in Tarla 49 station with heavy clay alluvial soils, Üçgedik, the Amik Plain. Tensiometric moisture potentials in the 0-30, 30-60, and 60-90 cm layers varied from 3.8 to 16, from 12 to 16, and from 15 to 20 kPa, respectively. Drain flows of 3873 and 15561l occurred according to the given moisture potentials 5 to 7 days after rainfalls. Water levels in piezometer battery (7-8-9), parallel to the flow channel of outlet, varied from high to low; 54-132, 72-122, and 117-152 cm, respectively. The piezometer battery (4-5-6), installed between laterals, registered very rarely high water table levels greater than drain depth of 100 cm. On the other hand, the piezometers (1-2-3) farthest from the drain outlet registered the highest water table levels varying from 133 to 96, 103 to 73, and 119 to 77 cm, respectively. The rains and infiltration were effective in 0-45 cm depth. The tensiometers in deeper depths responded to the rains between 4 and 6 days. Water table fluctuations were more effective than rains on the 90 cm depth tensiometers. Piezometer heads ranged from 44 to 157 cm in the spring and early summer and 0 to 44 cm for at least 24 days in the early spring. In conclusion, tile drainage system was operable effectively while runoff flow was ponding in the field. Therefore, a combined drainage systemcould remedy drainage hazard in the study area.