Hydrological simulation of the international catchment of Guadiana River

The intense and speed-up modification of the natural regime of the Guadiana River in the last four decades raised some concern about the effective wat er availability especially along the Portuguese-Spanish border. The beginni ng of the construction of Alqueva dam contributed to give more emphasis to this issue. The increase of the water storage in the Guadiana catchment, to satisfy the large water consumption from agricultural projects, caused mod ifications in the natural regime of the river. The Spanish storage capacity in the area increased from almost zero in 1954 to 4 000 hm(3) in 1963. Thi s value was kept almost constant until 1988, when a new increase almost dou bled the existing water storage capacity within three years. The coincidenc e of this increased storage capacity with drought periods felt in the early eighties and early nineties exposed the actual vulnerability of water reso urces in both southern Spain and Portugal. To characterize the vulnerabilit y of the water resources downstream of the Portuguese-Spanish border due to several upstream hydrological conditions and due to different sequences of humid and dry periods, a mathematical simulation model named IRAS (Interac tive River Aquifer Simulation) was used. This model allows to jointly simul ate surface runoff, water quality, underground flows and hydropower operati on. This paper discusses the procedures used to simulate time series of run off in the Portuguese part of the Guadiana catchment. Some of these time se ries reflect the influence of the schemes already installed others simulate d the hydraulic schemes to be installed. The scenarios of the Spanish Hydro logical Plan are considered as upstream boundary conditions. (C) 2000 Elsev ier Science Ltd. All rights reserved.