Abstract
AbstractChanges in water temperature can have important consequences for aquatic ecosystems, with some species being sensitive even to small shifts in temperature during some or all of their life cycle. While many studies report increasing regional and global air temperatures, evidence of changes in river water temperature has, thus far, been site specific and often from sites heavily influenced by human activities that themselves could lead to warming. Here we present a tiered assessment of changing river water temperature covering England and Wales with data from 2773 locations. We use novel statistical approaches to detect trends in irregularly sampled spot measurements taken between 1990 and 2006. During this 17‐year period, on average, mean water temperature increased by 0.03 °C per year (±0.002 °C), and positive changes in water temperature were observed at 2385 (86%) sites. Examination of catchments where there has been limited human influence on hydrological response shows that changes in river flow have had little influence on these water temperature trends. In the absence of other systematic influences on water temperature, it is inferred that anthropogenically driven climate change is driving some of this trend in water temperature. © 2014 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.
Highlights
Evidence for recent global warming comes mainly from observations of air temperature and near-surface sea temperature (Brohan et al, 2006; Hansen et al, 2006), but freshwater ecosystems are considered to be highly sensitive to temperature change (Bates et al, 2008; Yvon-Durocher et al, 2010)
Our models provide an estimate for the water temperature that could have been observed on any given day during the period of the time series
There may be some spatial structure to the distribution of warming and cooling sites, with apparent clustering of sites with cooling trends such as in Somerset in south-west England (Figure 1)
Summary
Evidence for recent global warming comes mainly from observations of air temperature and near-surface sea temperature (Brohan et al, 2006; Hansen et al, 2006), but freshwater ecosystems are considered to be highly sensitive to temperature change (Bates et al, 2008; Yvon-Durocher et al, 2010). Some aquatic species, such as salmonid fish, have thermal limits that determine the success of spawning, migration and survival (Hari et al, 2006; Wehrly et al, 2007). Water temperature regulates the amount of dissolved oxygen in rivers and the rate of biological and chemical processes with direct impacts on water quality and indirect impacts on biological responses (Whitehead et al, 2009)
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