Acta Geologica 43. (2000)

2. szám - E. Custodio: Groundwater-dependent wetlands

Acta Geologien Hungarica, Vol. 43/2, pp. 173-202 (2000) Groundwater-dependent wetlands Emilio Custodio Geological Survey of Spain, Madrid From the biological point of view wetlands are highly productive areas. They are of growing interest not only for wildlife, scenic landscape and recreation, but as a source of income and as a bioreserve. The times when wetlands were considered unhealthy and undesirable areas are fortunately over. However, in Europe and other regions many of them have already been desiccated, often by public initiative. Many wetlands or parts of them depend on groundwater contribution. This means less fluctuating situations than when they depend only on surface water, and physico­chemical characteristics are more stable. Associated vegetation is resistant to drought conditions when there is groundwater available at shallow depth. Not only is groundwater discharge to land surface important, but underground discharge as well, since this plays an important role in the water balance and especially in salinity and solute concentrations of local water. Groundwater-dependent wetlands can vary from small spots to large, elongated areas, from vegetation-rich areas to impoundings of spring water, and they may contain water from fresh to briny and with precipitated salts. Aquifer development may interfere (and often does) with groundwater availability to wetlands. Then there is an environmental conflict. Its solution means a trade-off between development and conservation, which is often a difficult one. This requires compromises by initially very diverse interests, as well as overcoming deeply entrenched myths. Obtaining reliable data and adequate monitoring is a necessary step. Key words: groundwater, wetlands, impact of development, role of groundwater, quality effects, delayed effects Introduction Wetlands are landscape features which can be found in almost all regions of the Earth. Surface areas vary from less than one hectare to many km2. They are more frequent in flat areas, coastal zones and lowlands, especially if rainfall is relatively important and the terrain is poorly permeable, but they also appear in arid areas, where their relative importance is increased. Wetlands may develop along valleys, in the central areas of geologic basins, in deltaic areas at places where foothills grade into low permeability flatlands, and in may other situations ( Cowardin et al. 1979; González-Bernáldez 1988; Brinson 1993). The Ramsar Convention on wildlife and waterfowl classifies wetlands into marine, estuarine, lacustrine, riparian, paludial and artificial. Wetlands have been defined as surface features which conform to some of the following conditions: Address: E. Custodio: Department of Ground Engineering. Pol. Univ. of Catalonia, Gran Capita s/n, Ed. D-2, 08034 Barcelona, Spain. On leave to the Geological Survey of Spain (Instituto Tecnológico Geominero de Espana), Rios Rosas, 23, 28003 Madrid, Spain. Received: 14 September, 1999 0236-5278/2000/$ 5.00 © 2000 Akadémiai Kiadó, Budapest

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