Título:
The combined use of hydrogeological and hydrochemical data to explain the observed groundwater compo
Resumo:
In the Campina de Faro, Algarve, agricultural practices have a large impact on the groundwater composition. Nitrate concentrations have risen profoundly due to the extensive application of fertilisers. Excess water originating from irrigation practices returns to the aquifer and mixes with water from the regional groundwater system. This irrigation return flow is strongly concentrated due to high evapotranspiration and flushing of fertilisers. The concentration increase induces calcite precipitation and cation exchange, whereby Ca on the soil exchanger is replaced by Na. With a geochemical model this hydrochemical evolution can be simulated. The mixing in the aquifer allows application of a mixing cell model, that may then be used to calculate transmissivities and the change of the Cl concentration in time from the Cl mass balance. Results from the calculations appear to be in good agreement with hydrochemical observations. Near the coast, large drawdowns cause sea water intrusion, which increases Cl concentrations and induces cation exchange.
Autores:
T. Y. Stigter, V. E. A. Post, S. P. J. Van Ooijen, C. A. J. Appelo, A. M. M. de Carvalho Dill