Measurements of tritium specific activity levels and of temperatures in waters of the Torrejo´neTagus
reservoir (Spain) showed that their radioactive characteristics were basically influenced by the radioactive
liquid effluent from the Almaraz Nuclear Power Plant. This enters the Torrejo´neTagus reservoir via the
Arrocampo cooling reservoir, which exchanges water with the first. We studied the temporal and spatial
(in two dimensions) evolution of the mentioned parameters for years 1997 and 1998. The tritium levels
were found to be significantly correlated with temperature. Two numerical models were constructed for
a quantitative study of the tritium levels along Torrejo´n reservoir: a 1D model was used for the dispersion
of tritium along the whole length of the reservoir, and a 2D depth-averaged model was used for a detailed
study of the area where tritium is released into the reservoir. Both models solve the hydrodynamic equa tions, to obtain the currents induced by the exchanges of water between the reservoirs in the River Tagus
and Arrocampo, and the advection/diffusion equation to calculate the dispersion of tritium. In general, the
model results were in agreement with the experimental observationsJunta de Extremadura 2PR02A02
