Topographic effects on flow path and surface water chemistry of the Llyn Brianne catchments in Wales

Wolock, D.M.; Hornberger, G.M.; Musgrove, T.J.. 1990 Topographic effects on flow path and surface water chemistry of the Llyn Brianne catchments in Wales. Journal of Hydrology, 115 (1-4). 243-259.

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Topographic shape is a watershed attribute thought to influence the flow path followed by water as it traverses a catchment. Flow path, in turn, may affect the chemical composition of surface waters. Topography is quantified in the hydrological model TOPMODEL as the relative frequency distribution of the index , where a is the upslope area per unit contour that drains past a point and tanB is the local surface slope. Spatial distributions of were calculated for eight catchments in Wales on a 25 m × 25 m grid. Among the catchments, mean observed stream H+ concentration during high flow periods was highly correlated with the mean of the distribution. The steady-state gain of a transfer function (time series) model relating H+ to discharge was positively correlated with the mean of the distribution. These results suggest that during high flow periods, both the average stream acidity and the magnitude of fluctuations in H+ are conditioned by the topographic shape of the catchment. By performing a sensitivity analysis on TOPMODEL, we also show that as the mean of the distribution for a catchment increases, so does its theoretical likelihood to produce significant quantities of surface and near-surface runoff. Our observed results in the Llyn Brianne catchments are consistent with this theoretical expectation in that surface or near-surface runoff is often higher in acidity than are deeper sources of hillslope runoff.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Other
UKCEH and CEH Sections/Science Areas: _ Pre-2000 sections
ISSN: 0022-1694
Additional Keywords: Llyn Brianne, Wales
NORA Subject Terms: Hydrology
Date made live: 30 Nov 2010 16:02 +0 (UTC)

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