DIURNAL-VARIATIONS IN STREAM DISCHARGE AND THROUGHFLOW DURING A PERIOD OF LOW FLOW

During the drought of 1976, the hydrological response of Bicknoller Combe, Somerset, England, was characterised by a marked diurnal oscillation of stream discharge. Observations of throughflow also showed a clear diurnal variation. Soil water potential data from tensiometer records indicated a flow reversal to occur with flow towards the soil surface during the day, in response to intense evapotranspiration, and at night, the resumption of downslope soil water movement. Diurnal oscillation of stream discharge is seen as the direct result of changes in the size of the saturated wedge which are produced by the periodic variation in the rate of evapotranspiration. Observations of diurnal variation in the solute concentration of stream water are also briefly described. © 1979.