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The macrophytic vegetation of the Friedberger Ach, a tributary to the River Danube, and of three bordering ground water ditches was mapped six times within the period from 1972 to 1996 using the same method. Different characteristic features have been calculated by means of quantitative evaluation methods using the data available from this long-term study. The temporal dynamics of the macrophytic vegetation based on these studies over a 24 years period could be analysed using the "Relative Plant Quantity" (RPM) and the distribution pattern of five floristic-ecological river zones. Additionally, the recolonization of a formerly devastated macrophyte zone could be investigated by means of distribution diagrams and the "Mean Mass Indices" (MMT, MMO). From this analysis it took almost fifteen years for the macrophytic vegetation to reflect an improvement in the nutrient status of the water. In the ground water ditches examined there has been a tendency for siltation, especially in recent years. This is expressed mainly in the increasing dominance of amphiphytes and the almost total disappearance of hydrophytes. The waters of the Friedberger Au show a surprising consistency in their macrophytic vegetation over the past 24 years.

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