The water table of the Great Dismal Swamp changes with the seasons primarily because of the temperature and amount of rainfall and associated with the different seasons. During the summer months when the temperatures are high, more evaporation occurs and usually less rain falls. Also, transpiration plays a large part since plants are more active during the warm months, and so water is lost. This causes the water table to drop.

When the weather becomes cooler during the fall and winter months, the water table raises (on the average) to three to five inches above ground level. After these cooler months have passed, warmer weather returns in the spring. Gradually the water table drops back down below the surface. My data indicates that the drop starts somewhere between March and April.

This past summer (summer of 1997) the water table dropped extremely low due to the high temperatures and the long periods without any rainfall. At points in time, the water table dropped twenty inches below the ground's surface.