Plot and small-watershed scale runoff from two reclaimed surface-mined watersheds in Alberta

Infiltration excess overland flow has been identified as the dominant flow pathway in recently reclaimed surface mined watersheds as a result of compaction and sorting during the reclamation procedure. Therefore, there could be a fairly direct relationship between runoff generated from the hillslopes to that measured at the watershed outlet. A 3-year study was initiated in 1993 to determine how well surface runoff at a watershed scale could be predicted from 1-m(2) runoff frames placed on hillslopes in two reclaimed surface-mined watersheds in central Alberta. Runoff from the hillslope frames suggests outlet discharge should be high from the 3.4-ha Sandy Subsoil Watershed and much less for the 9.8-ha West Watershed, but the opposite occurred. Most of the hillslope runoff from the Sandy Subsoil Watershed infiltrated once it reached the channel and depression storage played an insignificant role in determining runoff. In contrast, most of the runoff from the West Watershed originated from rain falling directly on the saturated channel (depression storage) or near-channel saturated areas, rather than the hillslopes. Neither watershed runoff magnitude nor timing could be predicted from the same parameters for hillslope runoff frames for either reclaimed watershed. Copyright (C) 2000 John Wiley & Sons, Ltd.