EVALUATION OF DRAINMOD FOR SOUTHERN ONTARIO CONDITIONS

Abstract

DRAINMOD, a well-known water table management model, was evaluated with field measurements made in a subsurface-drained corn field in southern Ontario, Canada. Four test plots were monitored from July to October 1991 and from May to September 1992 for midspan water table levels and drain outflows under two water table management practices, i.e. subsurface drainage and subirrigation in 1991 with two replicates each and subsurface drainage and controlled drainage in 1992, also with two replicates each, under conventional (fall mouldboard plough) tillage treatment.The average absolute deviations between the average measured midspan water table depths and the predicted values ranged from 24 to 100 mm for conventional drainage, and 82 to 353 mm for controlled drainage/subirrigation. The corresponding standard errors ranged from 32 to 118 mm for conventionally drained and 98 to 435 mm for controlled drained/subirrigated plots. The average absolute deviation between the measured and predicted drain outflows and the corresponding standard errors ranged from 0.28 to 0.36 mm/d and 0.76 to 0.90 mm/d, respectively, for the conventionally drained plots.The above values for the statistical parameters are comparable to the values obtained elsewhere in similar studies. From the two years of evaluations, therefore, it appears that DRAINMOD holds a lot of promise for designing and/or evaluating water table management systems in southern Ontario. However, the model should be evaluated at other sites in southern Ontario before any concrete conclusions are drawn.