2. Materials andmethods
2.1. Site description and sampling procedures
The Alqueva reservoir is located in southern Portugal, along 83 km of the main course of the Guadiana River Basin. The hydrologic regime of
the Alqueva reservoir reflects the regional expression of the Mediterranean
climate (Morales, 1993). During the study period, the climate was
characterised by a mean atmospheric temperature of 16 °C, ranging
from 3 °C in January to 33 °C in August (www.snirh.pt, 2010/2011;
2011/2012). The average monthly precipitation for the hydrologic year
2010/2011 was 46.5 mm (www.snirh.pt, 2010/2011) and 20.3 mm for
the hydrologic year 2011/2012 (www.snirh.pt, 2011/2012). Thus, the
precipitation values in the hydrologic year 2011/2012 were extremely
low compared to the previous year. The land uses obtained from the
Coordination of Information on the Environment (CORINE) land cover
classes (2006) identify agricultural activities as being the most ubiquitous
in the Alentejo region (68.8%), followed by semi-natural areas
(28.1%)