We revisit the serial discontinuity concept (SDC), which predicts river eco
system responses to stream regulation in the context of recovery with dista
nce downstream from the dam (discontinuity distance). Many studies have des
cribed pervasive interruptions of natural biophysical gradients of dams by
comparing conditions in tailwaters to reference or pre-impoundment conditio
ns. But only a few studies provide data or interpretations that explicitly
test the SDC within entire stream corridors or along specifically defined r
eaches where recovery was expected in view of the predictions of the SDC. W
e present discontinuity distance measures for nine rivers around the world
where the predictions of the SDC were substantiated. In two cases, recovery
trajectories were overwhelmed by other human sources of disturbance. In on
e case, the SDC did not hold up, but only biotic measures were made. We con
clude that, in general, the SDC is a sound construct that in most cases can
be used to predict, or at least clearly articulate, the consequences of ne
w regulation. The next step is to develop better empirical models of the SD
C and to validate them experimentally through re-regulation of entire river
corridors. Copyright (C) 2001 John Wiley & Sons, Ltd.