[en] Siting studies for SKB's programme of deep geological disposal of nuclear fuel waste currently involves the investigation of two locations, Forsmark and Simpevarp, on the eastern coast of Sweden to determine their geological, geochemical and hydrogeological characteristics. Present work completed has resulted in model version 1.1 which represents the first evaluation of the available Forsmark groundwater analytical data collected up to May 1, 2003 (i.e. the first 'data freeze'). The HAG group had access to a total of 456 water samples collected mostly from the surface and sub-surface environment (e.g. soil pipes in the overburden, streams and lakes); only a few samples were collected from drilled boreholes. The deepest samples reflected depths down to 200 m. Furthermore, most of the waters sampled (74%) lacked crucial analytical information that restricted the evaluation. Consequently, model version 1.1 focussed on the processes taking place in the uppermost part of the bedrock rather than at repository levels. The complex groundwater evolution and patterns at Forsmark are a result of many factors such as: a) the flat topography and closeness to the Baltic Sea resulting in relative small hydrogeological driving forces which can preserve old water types from being flushed out, b) the changes in hydrogeology related to glaciation/deglaciation and land uplift, c) repeated marine/lake water regressions/transgressions, and d) organic or inorganic alteration of the groundwater caused by microbial processes or water/rock interactions. The sampled groundwaters reflect to various degrees modern or ancient water/rock interactions and mixing processes. Based on the general geochemical character and the apparent age two major water types occur in Forsmark: fresh-meteoric waters with a bicarbonate imprint and low residence times (tritium values above detection limit), and brackish-marine waters with Cl contents up to 6,000 mg/L and longer residence times (tritium values below detection limit). The meteoric water is found at the surface and at shallow depths and the marine water is found closer to the coast and at depths affected by Baltic Sea water and probably old Litorina Sea water. The present state of knowledge of the reactive system is that the main water-rock interaction processes that affects the chemistry in the fresh meteoric waters are: 1) decomposition of organic matter, 2) calcite, plagioclase, biotite and sulphide dissolution, 3) Na-Ca ion exchange, and 4) phyllosilicate precipitation probably extremely slow in the present environment. For the brackish-saline groundwaters in contrast, the water/rock interaction processes seem to be less important although this has not been established because of a lack of data. At the moment multiple end-member mixing between marine water, glacial melt water and a deeper saline water seem to play a significant role. Based on presently available data, the groundwater sample at 115 m depth, i.e. not representative of repository depths, met the groundwater criterion established by SKB concerning the measured Eh, pH, TDS and Ca+Mg values. The redox system at this depth is controlled by the presence of iron oxides, hydroxides or by sulphide minerals. In this evaluation the post glacial groundwater scenario model has been updated, the salinity distribution, mixing processes and the major reactions altering the groundwaters have been modelled down to a depth of 200 m and a new Hydrogeochemical Site Descriptive Model version 1.1 has been produced. A 3D groundwater description of the site was not produced at this stage due to a lack of observations reflecting spatial variations. The possibilities to compare and integrate future hydrochemical modelling with hydrogeological modelling has improved due to major development in constructing hydrogeological site models. The salinity distribution in fractures and the rock matrix together with mixing proportions can be compared from two independent models