Plynlimon research: The first two decades

In the course of a long-term scientific experiment, there is a continuous process of reassessment and revision. As the results come in, it is possible to make amendments to the instrument network, and to incorporate new. or additional instrumentation as it becomes available. Over the duration of the Plynlimon experiment, the technology of microelectronics has made dramatic progress, and the labour-intensive instrumentation installed at the start of the study has largely been replaced by solid-state devices, freeing staff for the more interpretive aspects of the project. As a stage in the review of the Plynlimon project, it was decided to assemble the data from the experiment, including both the catchment data and the results of process studies and water quality studies undertaken at Plynlimon, in an intemal report that could form the basis for planning future changes in the direction of work at Plynlimon. The preparation of that report was a valuable exercise that has been instrumental in the shaping of the Plynlimon station as it now exists. It was felt that the report, with some modification, could be of interest to a more general readership. Thus the long process leading to this document began. The Plynlimon report has many authors and draws on the expertise of many sections of the Istitute of Hydrology, at Plynlimon and at Wallingford. Research of the scale and duration of the Plynlimon project relies on the collaboration of several different groups. The consequent involvement of many different staff over the years has had the advantage of bringing new dimensions, new insights and new talents to bear. It also makes it difficult to decide upon the right time to draw conclusions as there is always the tantalising possibility that a little more data will add a new dimension. In presenting this report, therefore, it has been decided to focus on the Plynlimon results as they stood at the end of 1985, but also to incorporate some of the more recent, exciting developments. A fuller scientific account of the Plynlimon results is to be found in the many journal papers, books and other publications, most of them referred to in this report.