Paulo Alexandre Diogo (Portugal) 1; João Pedro Nunes (Portugal) 2; Pedro Bea (Portugal) 1; Anótnio Carmona Rodrigues (Portugal) 1; Cláudia Carvalho Dos Santos (Portugal) 3; João Rocha (Portugal) 4
1 - Faculty of Sciences and Technology, New University of Lisbon, MARE; 2 - Faculty of Sciences, University of Lisbon; 3 - CIBIO-InBIO - Universidade do Porto; 4 - Universidade de Aveiro
Climate change scenarios for the Mediterranean region point to a likely decrease in mean annual precipitation and more frequent extreme precipitation events. These changes represent significant challenges to water resources management, as existing reservoir storage capacity might not be able to cope with the larger disparity between wet and dry periods, and the longer duration of droughts. This problem is already affecting southern Portugal; in 2017, most reservoirs used both for urban supply and irrigation were unable to supply demands and had to depend on water transfers from the strategic water reserve in the Alqueva reservoir (Guadiana river; 3.1hm3 total storage capacity).
Aiming to evaluate climate change impacts on water quantity and quality, insure adequate water safety and optimize energy costs associated with reservoir water transfers, the GestAqua.AdaPT project was develop for the reservoirs of Monte Novo and Vigia, both used as water sources for the district of vora (90000 inhabitants) and irrigation. Climate change scenarios were determined using EURO-Cordex results. Multiple global climate models and regional models combinations were analyzed and the Soil and Water Assessment Tool (SWAT) eco-hydrological model was used to simulate runoff impacts and phosphorous inputs into both reservoirs. Once the water balance for both reservoirs was calculated, reservoir water quality was simulated using the model CE-Qual-W2. This is a vertical-longitudinal 2D model considered particularly accurate to simulate temperature and water quality in stratified and reservoirs.
By means of this cascade of modelling results approach, the GestAqua.AdaPT project led to the conclusions that climate change may a) increase eutrophication, thus representing a threat to water quality in both reservoirs and b) increase monthly and annual inflow irregularity, causing greater risks associated with water storage reliability. GestAqua.AdaPT was intended to provide a significant contribution to improve knowledge and water management routines, through a better understanding of climate change impacts on water resources, with emphasis on the effects of extreme phenomena such as droughts and floods. The study area is also representative of multi-purpose water supply systems, thus the methods and obtained results may be exported to similar systems, improving the development of adaptation strategies in the water sector in general. These factors establish valid contributions to a more sustainable use of water, through better planning and management of water resources in situations of scarcity, as well as the development of emergency response plans.
The GestAqua.AdaPT project has been supported by the Adapt Program.