Acta Geologica 43. (2000)
2. szám - E. Custodio: Groundwater-dependent wetlands
174 E. Custodio a) areas with still water not forming lakes. That is, with a shallow water depth allowing waterfowl to feed and breed at least in a large part of them, b) areas with a shallow water table which can be used most of the time by plant roots to get water from the aquifer or the capillary fringe, c) areas in which évapotranspiration is greater than precipitation. These definitions are not accepted by all scientists and water managers but they are useful to decide what a wetland is. Wetlands may grade into lakes and into rivers. They can be more or less permanent or seasonal, or even something that fully develops only during and after wet years. Fluctuation is for some wetlands an important characteristic. Generally they contain fresh water, but saline water is found in coastal areas as well as in some continental situations in which salinity may grade from brackish to briny with associated precipitated salts. Wetlands have been historically - and in some cases they still are - regarded as wasteland and unhealthy areas, a source of malaria and other water-borne diseases, a nuisance to human life and much wanted flatland for cultivation and human establishments. Thus, since old times they have been the subject of destruction by infilling and by drainage. In Europe and other developed regions a large fraction of existing surface area has already been destroyed and irreversibly transformed, up to 80% according to some figures. Regulations fostering this behavior still persist in some countries, especially in developing nations and in tropical areas, where health concerns are still real. Lay people are generally predisposed against wetlands. This is to some extent rooted in legends and myths, and derives from a poor understanding of the environment. In fact large surface areas of wetlands were destroyed and still continue to be in many areas of the world. The situation is being redressed, however, mostly in developed countries, where environmental concern is now part of daily life and where the economic value of wetlands begins to be widely recognized (Llamas et al. 1992; Barbier et al. 1997). Wetland study and evaluation is a current issue in many countries, such as the USA (Adams et al. 1991) and the European Union. In Spain wetlands are now protected (at least in theory) by the Water Act. The River Basin Water Authorities, in charge of water management, have the duty of inventorying, monitoring and protecting wetlands, with objectives that must be included in the Plans for River Basin's Water Management. Wetlands are important areas. This is because of the benefits they bring, from the natural, economic, and aesthetic points of view, and which are related to the: a) very high organic matter production, b) large diversity of plant and animal species, c) beneficial effects on the water cycle, since they contribute significantly to regulate variability (e.g., smoothing floods), to retain nutrients, to foster water quality improvement and regularization, and to shape local climate and mitigate its fluctuation, Acta Geologica Hungarica 43, 2000