Patterns of reservoir operation over a 20-years period in the Guadalquivir basin and implications for basin management

Water management in basins where natural flow regime is altered by the presence of reservoirs is a complex issue that often requires the development of modelling tools to support managers in their decision-making process. However, when it comes to large basins where it is necessary to satisfy the different demands of a vast and heterogeneous territory, in which the pressures on the basin water resources are increased due to the effects of climate change, it makes modelling a challenging matter. It is in these cases when it is possible to use long series of data on hydro-meteorological variables collected in the basin reservoirs and stations to analyse the behaviour of the basin and its management over the period for which data are available.

A series of 20-years of hydro-meteorological data has been used in more than 30 reservoirs in the Guadalquivir River basin, in southern Spain, in order to obtain patterns of inflow and outflow regimes in the reservoirs, and to relate them to the supply to the different water demands. To do this, a distinction has been made between dry, medium and wet years, based on the SPI-12 in the basin. In order to obtain the patterns related to the natural regime of the basin, the headwater reservoirs have been selected, which do not have the inflow regime altered by the action of another reservoir upstream.

The results of the analysis show 5 different types of inflow-outflow dynamics depending on their location in the basin, that is, depending on the influence of the Mediterranean-Alpine climate in the upper areas of the basin, or the Atlantic influence near the mouth of Guadalquivir River. In addition, changes in management patterns have been identified depending on the type of year. Our results will be the basis for the development of management tools in large basins for short and medium-term forecasting of resource availability and demand satisfaction.