Investigation of water-table response to tile drains in comparison with theory

Abstract

An investigation of the performance of tile laterals, selected from farm drainage systems, is reported. Useful theories of water-table response to tile lines are briefly reviewed. The field procedure used for the investigation is described. Average hydraulic conductivity was determined from in-place measurements by the auger-hole and piezometer methods. The position of the impermeable layer was determined from textural examination of the soil and from piezometer measurements of hydraulic conductivity. The performance of laterals was investigated by simultaneous measurements of water-table height along lines at right angles to the tile and rate of discharge from the tile line. It is concluded that Hooghoudt's theory is adequately supported where flow boundaries can be sharply defined. The field data also support Kirkham's analysis, where the physical assumption underlying this analysis is reasonably met. Field data on the rate of lowering of the water table generally support Glover's analysis, although some caution appears to be necessary when using his analysis for design in cases where there is an impermeable layer at a small distance below the tiles. Comparison of the data with theory also shows that average values obtained of factors used in design and those indicating performance are satisfactory, though field variability is high. The adaptability of field data to theoretical simplifications is emphasized.