Ecological assessment of Mediterranean reservoirs: Alqueva reservoir as a case study (Alentejo, Southern Portugal)

Ecological assessment of Mediterranean reservoirs: Alqueva reservoir as a case study (Alentejo, Southern Portugal) Manuela Morais, Maria Helena Novais, Susana Nunes, Joana Rosado, Alexandra Penha, Amely Zavattieri, Miguel Potes & Rui Salgado Abstract The Mediterranean region, with almost 7% of the world population, has less than 3% of the world freshwater resources, and these are irregularly distributed, 72% in the northern countries (Spain; France; Monaco, Italy, Greece, Malta, Slovenia, Bosnia-Herzegovina, Croatia, Montenegro and Albania) 20 % in the eastern countries (Turkey, Syria, Lebanon, Israel, Palestinian Territories and Cyprus) and the remaining 8% in the Southern countries (Egypt, Libya, Tunisia, Algeria and Morocco) (Aquastat, 2011). Mediterranean Climate Regions occur between 30°- 45° North and South of the Equator, in the west side of continents of the Mediterranean Basin, Middle East California, central Chile, Western Cape in South Africa, and the South West in Western Australia. Correspond only to 2% of the Earth’s land surface. Also Jordan and the southern part of Portugal are included in the list, because lacking Mediterranean coast, they benefit from a similar climate and face analogous water scarcity and problems. The total population of the Mediterranean countries grew from around 300 million in 1970 to 466 million in 2010. The population is predicted to reach 500 million by 2025. This overgrowing population is increasing water resources pressure and requesting new water planning and management approaches. A Fresh Water Eco-region of Southern Iberia contains two of the largest rivers in the Iberian Peninsula: the Guadiana and the Guadalquivir. The Eco-region also include the largest manmade lake in Europe, the Alqueva Reservoir. Reservoirs are impoundments created by humans. They are being constructed on an unprecedented scale in response to the exponential water demands to human activities. Such alterations will result in major modifications in topography and regional climate that are not yet fully recognized or even partially understood. For this reason, recently the Water Laboratory participate in ALEX2014 (Alqueva Hidro-Meteriological-Experiment) in cooperation with ITC (Earth Science Institute) of University of Évora; and other Portuguese and International Institutions. The ALEX2014 campaign was planned in order to understand and predict the complex interactions between climate, hydrology, ecosystem processes, water quality and biodiversity for a future sustainable management of Mediterranean systems (Salgado et al., 2014). Between others, main results of the ALEX campaign are destined to improve the representations of lakes NWP models (to improve weather forecast and access climate impacts of man-made lakes; fulfill the requirements of the Water Framework Directive and improve the environmental and biological management of the reservoir. To go further on the understanding of the functioning of large and deep reservoirs during the summer period in the Mediterranean Region, Alqueva reservoir was studied from June until September 2014. To do so, vertical profiles of temperature, dissolved oxygen, pH, oxidation-reduction potential and conductivity were monthly taken. Simultaneously, water samples were collected for physical-chemical analyses and an integrated sample, representative of the euphotic zone, was collected for phytoplankton identification and quantification