Base flow characteristics of a subsurface-drained watershed.

摘要

An estimate of base flow composition of total flow volume was obtained by a mass balance of channel flow performed on a 189.75 m section of drainage channel, in the subsurface-drained Upper Little Vermilion River watershed (ULVR), in Champaign County, Illinois, USA. Total flow volume was measured at 15-minute intervals, with two V-notch weirs, at an upstream and a downstream section of the channel. Due to channel geometry, base flow was the only source for flow addition between the two weirs. A unit base flow volume estimate was calibrated by least square error estimates, for dry-weather periods, from October 1999 through August 2000. An average wet-weather period was found to contain 86% base flow by volume (20% S.D.), producing a range of 66 to 100% base flow composition. A relationship between base flow and channel flow was derived. Base flow was also correlated with contributing rainfall volume to create a model that could be applied to watersheds with similar hydrologic characteristic. A rational hydrograph separation technique was established to partition base flow from tile flow, based upon the correlation between rainfall volume and base flow volume..