Our purpose in this bulletin is to report, to analyze, and to use in problem solving, extensive model data of tile drainage of land.

The data were obtained with a glassbead-glycerol model (Grover et al., 1960; Grover and Kirkham, 1961) and inc1ude: (a) values of depths and of corresponding times of fall of the surface of saturation to these depths at various distances from the drain tubes and (b) values of the drain tube discharge rates. The zero reference time for the fall of the surface of saturation and also for the discharge rate is the instant at which the surface of saturation passes through the simulated soil surface from a ponded condition.

Models were made of 109 different combinations of drain depth, drain spacing and soil stratification. For each of these 109 model conditions, the surfaces of saturation were photographed at about eight different depths through the transparent front face of the model. Photographs were read under a magnifying glass to obtain distances and times of fall. Times were obtained from a clock that was started at the zero reference time and photographed with the water tables.