Hydrological simulation of the international catchment of guadiana river

Abstract 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 water availability especially along the Portuguese -Spanish border. The beginning 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 modifications in the natural regime of the river. The Spanish storage capacity in the area increased from almost zero in 1954 to 4 000 hm3 in 1963. This value was kept almost constant until 1988, when a new increase almost doubled the existing water storage capacity within three years. The coincidence of this increased storage capacity with drought periods felt in the early eighties and early nineties exposed the actual vulnerability of water resources in both southern Spain and Portugal. To characterize the vulnerability 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 (Interactive River Aquifer Simulation) was used. This model allows to jointly simulate surface runoff, water quality, underground flows and hydropower operation. This paper discusses the procedures used to simulate time series of runoff in the Portuguese part of the Guadiana catchment. Some of these time series reflect the influence of the schemes already installed others simulated the hydraulic schemes to be installed. The scenarios of the Spanish Hydrological Plan are considered as upstream boundary conditions.