Simulations of phytoplankton dynamics in El Gergal Reservoir, Southern Spain (PROTECH)

The Mediterranean region is characterised by a variable climate with most of the rain falling during the winter and frequent summer droughts. Such warm, dry periods are ideal for the growth of large algal blooms that often consist of potentially toxic Cyanobacteria. This makes the management of water for human use particularly challenging in such a climate and it is important to understand how such blooms can be avoided or at least be reduced in size. PROTECH (Phytoplankton RespOnses To Environmental CHange) is a model that simulates the dynamics of different species of phytoplankton populations in lakes and reservoirs. Its distinct advantage over similar models is its ability to simulate the relative composition of the algal flora, allowing both quantitative and qualitative conclusions to be drawn e.g. whether Cyanobacteria could be a potential problem. PROTECH has been applied primarily to lakes and reservoirs in northern Europe. Recently, however, the model has been applied to water bodies in lower latitudes, including Australia to a water supply reservoir in the south of Spain, El Gergal. El Gergal is the last in a chain of reservoirs that supply water to the city of Seville. It was brought into service in April 1979 and has a maximum storage volume of 35 000 000 m3. This article summarises the application of PROTECH in order to simulate the following problems: • the effect of a large influx of Ceratium biomass into El Gergal from another reservoir • the effect of using alternative water sources instead of the Guadalquivir River (used occasionally to raise water levels in El Gergal) • the effect of installing tertiary sewage treatment on the Cala River • the effect of simulated drought conditions on phytoplankton in the reservoir