|
southwest Iberian Peninsula Associated Investigators: Related Web Sites: Related Time Series: The Guadiana Lower Estuary sampling site is located between 37 13' 15.03" N, 007 24' 49.86" W and 37 07' 44.04" N, 007 24' 06.36" W, and includes two sampling stations, in the estuary mouth and in the plume (stations G1 and G2, respectively), in a water depth ranging from 5 to 30 m (Figure 1). The Guadiana site is a mesotidal estuary with an average amplitude of 2 m ranging from partially stratified to well-mixed, an average depth of 6,5 m and an area of 22 km2. It can be divided into three sub-areas: upper, middle and lower estuary (Chicharo et al., 2001). The lower estuarine area is influenced by extensive saltmarshes areas and the salinity is usually very close to that of seawater (>20). The Guadiana estuary is located in the Northeastern Atlantic but under the influence of the Mediterranean climate, natural river inflows typically vary markedly, within and between years, as a result of seasonal and annual fluctuations in rainfall. In addition to this natural variation in freshwater discharge into the estuary, extensive urban and agricultural development in the Guadiana River basin (fourth largest river basin in the Iberian Peninsula (67480 km2), mainly since the 1950s, such demanding conditions lead to the construction of hundreds of dams. Recent construction of the large Alqueva dam, built in the upper estuary in 1999 and completed in 2002, further increased freshwater flow regulation, and according to international agreement made between Portugal and Spain, the average daily flow in lower riverine areas cannot be lower than 2m3 s-1 (Chicharo et al. 2006). As a consequence, the Guadiana estuary shifts between being freshwater dominated during winter and flood periods, and registering a marine influence during most of the year. The Guadiana estuary is also influenced by weak upwelling events (Morais et al. 2009). REFERENCES: Bunn S, Arthington A (2002) Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30(4): 492-507 Chicharo M. A., L. Chicharo, H. Galvao, A. Barbosa, H. Marques, J.P. Andrade, E. Esteves, C. Miguel, C. Gouveia (2001) Status of the Guadiana estuary (South Portugal) during 1996-1998: an ecohydrological approach. Aquatic Ecosystem Health and Management, 4, 73-90. Chicharo L., M.A. Chicharo, R. Ben-Hamadou (2006) Use of a hydrotechnical infrastructure (Alqueva Dam) to regulate planktonic assemblages in the Guadiana estuary: basis for sustainable water and ecosystem services management. Estuarine Coastal and Shelf Science,70, 1-2: 3-18. Molinero, J. C., Ibanez, F., Nival, P., Buecher, E., and Souissi, S. (2005). The North Atlantic climate and the northwestern Mediterranean plankton variability. Limnology and Oceanography, 50: 1213-1220 Morais P, M.A. Chicharo, L. Chicharo (2009) Changes in a temperate estuary during the filling of the biggest European dam, Sci Total Environ, 407: 2245 - 2259 |