Monitoring change in hydrological systems

Monitoring is the process by which we keep the behaviour of the environment in view, providing essential information on how systems are changing and how fast, and allows us to learn to adjust what we are doing to get the best out of the system. This paper reviews the ways in which long-term study of the natural environment can be achieved. Three hydrological examples are then presented: nitrate leaching in a small agricultural catchment in south west England; the impact of drought on the peat-covered headwaters of the River Tees in northern England; and the impact of clear-felling on forest hydrology and nutrient export in the southern Appalachians. Monitoring programmes, if well designed and properly maintained, can provide important evidence of environmental change, revealing unexpected patterns and stimulating experimental research. The existence of long, reliable data sets considerably increases our ability to make informed decisions about the way in which we manage our river catchments.