Performance Evaluation of Pipeless Drainage: A Case Study in the Central Plain of Thailand

Abstract

The productivity of acid sulphate heavy clayey soils of the Central Plain of Thailand is severely hampered by their poor drainage capability. A field-oriented study was conducted to assess the performance of a pipeless drainage system in terms of soil improvement. A total of eight pipeless drains were constructed at 1% slope having drainage base and drainage spacing of 55 cm and 2m, respectively. In addition to the hydraulic assessment of the drains, crack observation (staining test), in situ hydraulic conductivity measurement, and pertinent chemical analyses of drain-effluent were carried out. The individual drain-response time varied considerably among the drains themselves as well as among six observed irrigations. The drain-discharge hydrographs were found to be highly influenced by the surface cracks caused by long-term drying. These cracks enhanced the drain-discharge by about 15 to 20 times the normal draindischarge; such enhanced discharge is not desirable and hence should be avoided. The drainage system in general effectively regulated the water flow through the soil profile. The staining test further confirmed the presence of macropores (cracks/fissures) up to an appreciable depth in the drained plot. Consequently, its hydraulic conductivity increased by a factor of about 4.3. Additionally, the pipeless drainage system provided promising results concerning acidity and/or toxicity attenuation of Bangkok's acid sulphate soil.