Long term water temperature behaviour and trends in a Devon, UK, river system

Abstract

Abstract Data collected over a 14 year period (1977–1990) at three river stations have been used to study long term behaviour, trends and possible future changes of water temperature in the Exe Basin, Devon, UK. Long term mean temperatures are influenced by site elevation and catchment land use. Seasonal variation approximates a simple sine-generated curve and diurnal fluctuation is greater in spring than in autumn months. Significant rising trends were evident for the majority of water temperature parameters investigated and were related to air temperature changes and land use effects. Coupling of possible scenarios for future air temperature change with relationships between mean air and water temperatures and between extreme and mean water temperatures, suggests that significant increases in stream temperatures may occur by the middle of the next century, especially in small upland catchments during summer months.