EVALUATION OF 2 WATER-TABLE MANAGEMENT MODELS FOR ATLANTIC CANADA

Two water-table management models, DRAINMOD and SWACROP, were compared and contrasted using the field measurements made at a 5.4 ha experime ntal site in Atlantic Canada. Three drainage treatments, consisting of 3, 6 and 12 m drain spacing, were used to measure the subsurface drai n outflows and the corresponding midspan water-table depths during the summer months of 1990 and 1991. Several statistical parameters, i.e. the average mean of differences, the average absolute deviations, the standard errors of estimate and the standard deviation of the differen ces, were used to compare the measured values with the values simulate d by the two models. Both models did a comparable job by yielding valu es close to the measured ones. They were quite sensitive to the rainfa ll events; the simulated drain outflow rates were usually higher than the measured values during and right after the rainfall events. The di fferences between the two models were quite obvious after the rainfall events, especially the ones after dry spells. On the whole, the two m odels were simulating water-table depths and drain outflow rates quite close to each other. Therefore, it can be stated that both DRAINMOD a nd SWACROP can be used to design subsurface drainage system in Atlanti c Canada. However, improvements are needed in both models to simulate better under rainfall events, especially those following a prolonged d ry spell.