Scales of hydroecological variability within a groundwater-dominated stream

This paper aims to show how hydrological, ecological and climatological dat a may be analysed to assess the temporal and spatial scales at which hydroc limatological variables influence instream ecology. A groundwater-dominated chalk stream (Little Stour River, Kent, UK), for which ecological data are available over 6 years (1992-1997), provides the focus for the testing and application of these techniques. Correlation and regression analyses are u ndertaken to highlight the dominant hydroclimatological factors influencing community abundance at a range of spatial scales encompassing: the entire river, upstream and downstream sectors, habitat type (riffle) and individua l riffle sites. To set these results in a longer-term context, temporal seq uencing of annual air temperature and discharge regimes is undertaken (base d upon 30 years of data, 1969-1999). A classification of annual discharge h ydrograph 'shape' and 'magnitude' identifies years with early, intermediate or late peaks, which may be assigned into three magnitude groups. Four ann ual air temperature 'magnitude' classes are apparent. The regime analysis c learly reveals inter-annual variability in both these key physical habitat parameters. Analysis of variance indicates a significant difference in macr oinvertebrate community abundance for the hydrograph 'shape', 'magnitude' a nd combined classes identified at all scales of analysis, although the infl uence of air temperature only varied significantly between riffle sites. Th e techniques used may be easily adapted to water resource management. Copyr ight (C) 2001 John Wiley & Sons, Ltd.