What Does Waterlogged Mean?
Wood becomes waterlogged when all its cells are filled with water. It can absorb water only up to about 30 percent its own weight. As it does so, the wood swells until it reaches “fibre saturation point” or its maximum volume. If further water is added, it will penetrate to the cavities of the cells, but no further swelling will take place. Waterlogged wood no longer floats because the air space within are filled with fluid making it too heavy.
Waterlogged wood is found in underwater or excavated archaeological sites. The wood artifacts have often endured in the ground sometimes for centuries. They are found in areas such as bogs, bottom of lakes, oceans, rivers and glaciers. Excavated wood is found buried in the ground in damp soil and in most cases retains a high percentage of moisture. This excavated wood can be treated the same way as waterlogged wood.
Since water soaks in and fills the cell walls of archaeological waterlogged wood, when removed from the water and dried, the tangential shrinkage can be 50-75% compared to 5-10% shrinkage in freshly cut wood. When left to dry on its own, this leads to radical shrinkage and degradation of the wood. Thus, a conservation treatment must be used to preserve the shape of these archaeological artifacts.
The word “waterlogged” is used to describe ships that have been flooded and sunk, or meadows and fields that are so wet that they must be drained before they are any use of growing food. A meadow becomes waterlogged in the same way as wood. The land can no longer absorb more water or drain it away. Many areas of land remain permanently in this condition unless they are reclaimed for farming.
Soil may be regarded as waterlogged when it is nearly saturated with water much of the time such that its air phase is restricted and anaerobic conditions prevail. In extreme cases of prolonged waterlogging, anaerobiosis occurs, the roots of mesophytes suffer, and the subsurface reducing atmosphere leads to such processes as denitrification, methanogenesis, and the reduction of iron and manganese oxides.
In agriculture, various crops need air (specifically, oxygen) to a greater or lesser depth in the soil. Waterlogging of the soil stops air getting in. How near the water table must be to the surface for the ground to be classed as waterlogged, varies with the purpose in view. A crop’s demand for freedom from waterlogging may vary between seasons of the year, as with the growing of rice (Oryza sativa).
In irrigated agricultural land, waterlogging is often accompanied by soil salinity as waterlogged soils prevent leaching of the saltsimported by the irrigation water. From a gardening point of view, waterlogging is the process whereby the soil blocks off all water and is so hard it stops air getting in and it stops oxygen from getting in.