Long-Term and Seasonal Changes in Chemical Composition of Surface Waters in Latvia

The changes of the chemical composition in Latvianinland waters over the last twenty years weredetermined, based on data of the National MonitoringProgramme. Relationships between the water compositionwere studied. The chemical composition and seasonalchange pattern depend a lot on hydrological factorswhich differed between eastern and western Latvia.Different pattern of long-term changes is found forsubstances which have different sources andsinks, at first for nutrients (decrease only in the lastfew years) and inorganic ingredients (commonlyincreasing trend). An attempt was made to identify themain sources of the major water ingredients and linkchanges of their concentrations with changes inloading to waters.