Innovative methodologies for the forecasting of ecological quality in reservoirs (Alqueva, south of Portugal)

Abstract

In the 21st century water scarcity is a reality that poses a threat to the biosphere and humanity. This situation represents an important limiting factor for socioeconomic development with frequent observation of transgressions. To exacerbate this scenario, future projections predict that the Mediterranean will become a sensitive region, with increased temperature and decreased precipitation and runoff.Atmosphere is a central component of the Climate System, playing a crucial role in the variability of its subsystems. The ecological conditions of the reservoirs clearly illustrate the high sensitivity and vulnerability of these systems, dependent on precipitation, air temperature and radiative parameters. The use of meteorological data combinedwith FLake models allows prediction of the evolution of water temperature and its quality in lakes and reservoirs.Alqueva is located on the Guadiana River in southern Portugal and is the largest reservoir in Europe. During the summer of 2014 (June to September) monthly campaigns (in same cases biweekly) were held on three platforms located in the lacustrinezone.In situ measurements (temperature, dissolved oxygen, pH, conductivity and oxidation-reduction potential) were obtained and water samples were collected for laboratory analysis of chemical (nitrogen and phosphorus) and biological parameters (phytoplankton). The obtained data were statistically tested, being also used to compare with the simulations of the Flake model.The results point to a dynamic system with an evolution over the summer, although dominated by cyanobacteria. The simulations with the FLake model demonstrated a good ft to real data, which shows the robustness of this methodology in the prediction of the evolution of the water temperature, important for the defnition of a warning system to support the decision in the scope of the integrated management of multi-uses aquatic systems.

Keywords: water reservoirs;ecological quality; prediction of the water temperature.