All in all, for four years the performance has been stable without any temporal trend.doi:10.1002/aheh.19900180112Dr. sc. techn. R. MeissnerH. TaegerDr. agr. F. SchulzDr. agr. habil. D. KramerWILEY‐VCH Verlag GmbHActa Hydrochimica Et Hydrobiologica...