PERFORMANCE OF UNLINED AND LINED MOLE DRAINS IN A SALINE CLAY LOAM FIELD

The performance of unlined and lined mole drains was studied in a saline, poorly drained, clay loam soil in southern Alberta. Both mole drains were operative throughout the 10-yr study and were effective in lowering the water table after each flooding. However, discharge from the unlined moles averaged 24% of that from the lined moles. Drain spacings were satisfactory for effectively lowering the water table, and were in satisfactory agreement with the spacing calculated at 29 h, using hydraulic conductivity (K) from drain discharge. The K value obtained by the shallow well pump-in method was 0. 02 cm/h. By the drain discharge method K was 0. 07 and 0. 22 cm/h for the unlined and lined mole drain areas, respectively, and by the water table recession method, it was 0. 17 and 0. 28 cm/h for the unlined and lined mole-drained areas. These data indicate vertical drainage was considerably greater than horizontal drainage, and that there was natural but slow internal horizontal drainage. Refs.