River temperature regimes of England and Wales: spatial patterns, inter‐annual variability and climatic sensitivity

Abstract

Abstract:Identification of the most sensitive hydrological regions to a changing climate is essential to target adaptive management strategies. This study presents a quantitative assessment of spatial patterns, inter-annual variability and climatic sensitivity of the shape (form) and magnitude (size) of annual river/stream water temperature regimes across England and Wales. Classification of long-term average (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006) annual river (air) temperature regime dynamics at 88 (38) stations within England and Wales identified spatially differentiable regions. Emergent river temperature regions were used to structure detailed hydroclimatological analyses of a subset of 38 paired river and air temperature stations. The shape and magnitude of air and water temperature regimes were classified for individual station-years; and a sensitivity index (SI, based on conditional probability) was used to quantify the strength of associations between river and air temperature regimes. The nature and strength of air-river temperature regime links differed between regions. River basin properties considered to be static over the timescale of the study were used to infer modification of air-river temperature links by basin hydrological processes. The strongest links were observed in regions where groundwater contributions to runoff (estimated by basin permeability) were smallest and water exposure time to the atmosphere (estimated by basin area) was greatest. These findings provide a new large-scale perspective on the hydroclimatological controls driving river thermal dynamics and, thus, yield a scientific basis for informed management and regulatory decisions concerning river temperature within England and Wales.

What causes cooling water temperature gradients in a forested stream reach?

“…Therefore, shading headwater reaches, where water is not in dynamic equilibrium with the atmosphere (e.g. Edinger et al, 1968;Hrachowitz et al, 2010;Kelleher et al, 2012;Garner et al, 2014b) and is thus cooler than the majority of locations lower in the basin (Poole and Berman, 2001), is anticipated to provide cool-water refugia for temperature-sensitive species and reduce temperatures further downstream.…”

“…Macdonald et al, 2003;Rutherford et al, 2004;Danehy et al, 2005;Moore et al, 2005; Published by Copernicus Publications on behalf of the European Geosciences Union. Gomi et al, 2006). Consequently, there is substantial interest from researchers and stream managers in the potential of riparian vegetation to mitigate against climate change impacts (e.g.…”

Changes in river water temperature between 1980 and 2012 in Yongan watershed, eastern China: Magnitude, drivers and models

“…Furthermore, lag times are positively correlated with the contribution of groundwater (Gu et al, 2014;Garner et al, 2014).…”

“…2). Higher percentage of developed area implies more impervious surfaces and yields more heated urban runoff to rivers (Kaushal et al, 2010;Lepori et al, 2014;Gu et al, 2014;Garner et al, 2014). The rapid runoff from impervious surfaces is also believed to partially contribute to a shorter lag time between changes in monthly air and river water temperature for the HG river segment (Fig.…”

“…Changes in the contribution of groundwater may also have a considerable influence on water temperature (Gu et al, 2014;Garner et al, 2014). It appears that the Yongan watershed had no significant change in groundwater contributions during the study period since there were no significant changes in the runoff coefficient (p > 0.05, Table 1) or water discharge (Fig.…”