1. Towards a network of automatic lake water quality monitoring buoys in the UK Background Microbial growth and physical processes, such as mixing events, typically operate over short time scales that are not captured by standard weekly, fortnightly or monthly sampling. Relatively recent advances in computer and sensor technology increasingly makes it possible to collect relevant data at minute time scales which match the time scales of important lake processes. Future applications A possible powerful future application is the coupling of process- based water quality models, such as PROTECH (Jones & Elliott, 2007), with current lake status measurements from monitoring buoys and forecasts of future weather. This may give lake and reservoir managers warning about possible future events that could be ameliorated by timely action. Figure 3: The difference between surface and bottom temperature for two neighbouring lakes in summer and autumn 2006. The black line is for a temperature difference of 1 o C and thus indicates when overturn occurs in the lakes. Management potential One use of the buoy data is for driving, calibrating and validating numerical models. An example is shown in Fig. 4, for Esthwaite Water using the ‘PROBE’ lake model of the Swedish Met. Office. Once such models are validated they can be used for many purposes, including to predict how lakes will respond to future climate change. The PROBE model, for example, showed an expected increase in stratification for Esthwaite Water of 25 days by 2070 (Persson et al., 2005). Figure 1: The deployment of buoys in the UK; those in red are operated by CEH, those in orange by partner organisations. Figure 2: An automatic water quality monitoring buoy. Figure 4. Observed (symbols) and modelled (lines) surface and deep water temperatures for Esthwaite Water, 1997–1998. Scientific potential Fig. 3 shows the temperature difference between the top and bottom of two neighbouring lakes, during the summer and autumn of 2006. Despite being subject to the same weather, morphological differences between the lakes – in this case surface area – caused the strength of temperature stratification to be very different. As a consequence the larger lake overturned 2.5 weeks before the smaller lake (Jones & Maberly, 2008). Such differences can have dramatic effects on hypolimnetic anoxia, fish habitat, and internal nutrient loading, but can only be effectively understood by continuous high resolution monitoring on the lakes. The buoys Each of the buoys (Fig. 2) carries a range of meteorological instruments, including air temperature, solar radiation, wind speed and relative humidity sensors and a chain of 12 in-lake temperature sensors. Additional instrumentation, to measure turbidity, pH, chlorophyll or oxygen have been fitted to some of the buoys, allowing high resolution physical and ecological interactions to be explored. The data can be telemetered back to the laboratory allowing the condition of a lake or reservoir to be checked in real-time. References Jones I.D. & Elliott J.A. (2007) Modelling the effects of changing retention time on abundance and composition of phytoplankton species in a small lake. Freshwat. Biol., 52, 988–997. Jones I. & Maberly S.C. (2008) Automatic in-lake modelling in the English Lake District. Verh. Internat. Verein.Limnol, 30, 70–72. Persson I., Jones I. Sahlberg J., Dokulil M., Hewitt D., Lepparanta M. & Blenckner T. (2005) Modelled thermal response of three European lakes to a probable future climate. Verh. Internat. Verein. Limnol., 29, 667–671. I.D. Jones & S.C. Maberly Centre for Ecology & Hydrology, CEH Lancaster, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP ianj@ceh.ac.uk, scm@ceh.ac.ukianj@ceh.ac.ukscm@ceh.ac.uk The network Within the UK, seven buoys are maintained by CEH: five in Cumbria, one in Scotland and one in Wales and a further four are maintained by colleagues in other organisations (Fig. 1). A spatial network not only provides detailed information about functions within a lake but also produces information on the extent of coherent behaviour across lakes and their comparative sensitivity to weather patterns. This will in turn provide valuable evidence for the response of lakes to climate change.