“…A classification of the impacts listed with respect to their timescale was given by Lijk1ema et al (1989) and is illustrated in Figure 2 Acute pollution denotes pollution of the receiving water body which, after a discharge event, does not have effects anymore, but only consequences (Harremoes, 1989;Rauch and Harremoes, 1996e). This type of pollution is frequently described by simple criteria such as frequency or percentage of time or by statistical criteria based on terms such as return period and exposure time.…”