The present study deals with correlation between level of ground water table and water content of peat in peatlands drained for forestry. The results have been obtained partly from field studies and partly from experiments in the laboratory.
Both the field and laboratory experiments proved that a close rectilinear correlation exists between the level of the ground water table and the water content of surface peat. A given change in the level of the ground water table corresponds to a smaller change in the water content the deeper the peat layer examined is situated. The change in the water content in the surface layer (0–20 cm) in the cases studied was of such a magnitude that a change of 10 cm in the level of the ground water table corresponded to a change of about 5 volume per cent. In deeper layers the change was smaller. The state of equilibrium regulating the water content of the peat is relatively stable. It is possible that the so-called optimum drainage of a peatland for each tree species can be theoretically determined on the basis of the correlation between the water content of peat and the level of ground water table.
The method used in the study, the repeated weighing of peat samples in their original place, has proved to be very useful and decisively better than the method based on one-time samples. The experiment also indicate that the correlation can be determined with laboratory experiments.