Ghabour, Th. K. Soils & Water Use Dept., National Research Centre, Dokki, Cairo, Egypt.

The wetlands are important ecosystems. They are among the world's most productive environments and provide a wide array of benefits. They have ecological, economical, and/or social values. These values are society's perception of the functioning of wetlands, and generally are desirable or useful to humans. Unfortunately, in spite of their significant importance, wetlands continue to be among the world's most threatened ecosystems, mainly because they are exposed to pollution or the over-exploitation of their resources. However, the most effective damage of all lays in their conversion to other land-uses which historically has been a problem and has continued to be till the present day. The current study aims to map and classify the wetlands in the northern middle portion of the Nile Delta of Egypt based upon the remotely sensed data. The Cowardin classification has been used in an inventory of wetlands and deepwater habitats. The structure of this classification is hierarchical processing from systems and sub-systems at the most general levels to classes and dominance types. The term system refers to a complex of wetlands and deepwater habitats that share the influence of similar hydrologic geomorphologic chemical or biological factors. The systems are further subdivided into more specific categories called sub-systems. The five major systems are marine, estuarine, riverine, lacustrine and palustrine. The studied wetlands are mainly estuarine and lacustrine fringes. These wetlands are exposed to high levels of pollution from industrial, domestic, and agricultural sources. Furthermore large parts of these wetlands are converted into other land uses. The estuarine system consists of deepwater tidal habitats and adjacent tidal wetlands that are usually semi-enclosed by land but have open, partly obstructed, or sporadic access to the open ocean or sea and in which sea water is at least occasionally diluted by fresh water runoff from the land. It includes both estuaries and lagoons. The lacustrine system includes permanently flooded lakes and reservoirs, intermittent lakes and tidal lakes with sea derived salinities below 0.5%. Water saturation largely determines how the soil develops and the types of plant and animal communities living in and on the soil. Wetlands may support both aquatic and terrestrial plant species. The prolonged presence of water creates conditions that favor the growth of specially adapted plants and promote the development of characteristic wetlands soils. The primary objective of this classification is to impose boundaries on natural ecosystems for the purpose of inventory, evaluation and management processes. Thus the outputs of this study are ready to be used for further wetland investigations.