Temporal and small-scale spatial variations of dissolved oxygen in the Rivers Thames, Pang and Kennet, UK.

Small-scale spatial dissolved oxygen concentrations were measured on three rivers by taking a number of transects along a river reach. Temporal (diurnal) variations were measured by use of continuous (15-min) monitors located at the mid-transect of the spatial observations. Spatial variation of dissolved oxygen concentrations were found to be relatively small (approx. +/- 10% dissolved oxygen) and biologically insignificant compared to diurnal changes under conditions of high productivity (approx. +/- 60% dissolved oxygen). The diurnal curves were analysed in order to estimate values of reaeration, photosynthesis and respiration on a daily basis for almost 3 months using process-based analytical techniques (the Delta and Hornberger and Kelly methods). The River Kennet was shown to be the most productive river followed by the River Pang and then the River Thames. The patterns of reaeration, photosynthesis and respiration and the behaviour of the three rivers are discussed.