The thermal characteristics and related hydrology of a pennine stream

Abstract

2An experimental catchment of 1 km(^2) was established at Lanehead in Upper Weardale to study the effects of atmospheric conditions upon stream water temperature. Discharge from the catchment was measured by a prefabricated wooden flat vee veir which was installed during the summer of 1968. Precipitation was measured at two sites in the catchment; standard and ground totaliser gauges, together with a Dines recorder gauge were installed at each site. Air, stream and ground water temperatures were recorded with thermographs at various sites within the catchment. Because the volume of discharge would have a modifying effect upon the relationship between the stream water temperature and the atmospheric conditions the rainfall/runoff relations in the catchment were studied. During the summer period this relationship varied according to the antecedent soil moisture condition. In the winter, when the precipitation was in the form of snow the release of discharge was controlled by other factors such as air temperature, humidity and solar radiation. The release of snow melt as discharge had a dominating effect upon the temperature of the stream water. The thermal characteristics of the stream water were found to vary in a three dimensional sense of time and- space. The water temperature at any point in the stream varied within the context of the diurnal air temperature cycle, the magnitude of this fluctuation differed with distance from the stream source, and finally the scale of both of these varied with the differing overall atmospheric environment which occurred from season to season. The stream channel exerted a strong influence upon the water temperature by virtue of the fact that it modified the influence of factors such as ear temperature and solar radiation.