Temporal variations in near surface soil moisture at two contrasting sites in the Wye catchment and their control on storm streamflow generation G. Roberts1 and S. B. Crane2 1Institute of Hydrology, Wallingford OX10 8BB, UK 2Institute of Hydrology (Plynlimon), Staylittle, Llanbrynmair, Powys, SY19 7DB, UK
Abstract. Near surface soil moisture measurements were recorded
at hourly intervals at two contrasting sites within the Cyff sub-catchment using a prototype
capacitance probe system. In a mire area within a valley bottom, over the twelve month
recording period, very little change in moisture content occurred. At the other site, a
well drained area on a steeply sloping hillside, major variations occurred with significant
soil moisture deficits being generated during a particularly dry summer.
Soil moisture on the slope responded rapidly to rainfall inputs during wet periods,
with little response during particularly dry periods. A number of rainfall events
was analysed to determine whether changes in soil moisture could be used to characterise
storm hydrographs for the Cyff and the Gwy, two sub-catchments being composed of differing
percentages of mire area and steep slopes. It was found that percentage runoff for the
Cyff was correlated with antecedent soil moisture on the slope, though the agreements for
peak flow and lag time were poorer. For the Gwy, poor agreements were obtained for all
three hydrograph characteristics. A simple formulation, based on storm rainfall and
antecedent soil moisture deficits in the slope and mire areas, gave good agreement with
storm streamflow volumes.
Citation: Roberts, G. and Crane, S. B.: Temporal variations in near surface soil moisture at two contrasting sites in the Wye catchment and their control on storm streamflow generation, Hydrol. Earth Syst. Sci., 1, 453-461, doi:10.5194/hess-1-453-1997, 1997.