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

Grace Garner,Jonathan P Sadler,David M Hannah,Harriet G Orr

doi:10.1002/hyp.9992

Grace Garner, Jonathan P Sadler + Show 2 more

Open Access

https://doi.org/10.1002/hyp.9992

Copy DOI

Abstract

AbstractIdentification 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 (1989–2006) 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. © 2013 The Authors. Hydrological Processes published by John Wiley & Sons, Ltd.

Highlights

In recent years, there has been an upsurge in river and stream temperature research (Hannah et al, 2008a) as temperature is increasingly recognized as an important and highly sensitive variable affecting biological, chemical and physical processes in flowing waters (Caissie, 2006)
Results are presented in three sections: (1) regionalization of long-term shape and magnitude regimes for river and air temperatures, to explore spatial patterns and identify regions that structure further analyses, (2) inter-annual river and air temperature shape and magnitude regimes, to assess between-region and within-region regime dynamics and air–river temperature sensitivity and (3) analysis of the influence of basin properties on air–water temperature regime sensitivity between and within regions
River temperature regimes peaked in July with minima in January; air temperature regimes exhibited an extended July–August maxima and January–February minima (Figure 3)

Summary

Introduction

There has been an upsurge in river and stream temperature research (Hannah et al, 2008a) as temperature is increasingly recognized as an important and highly sensitive variable affecting biological, chemical and physical processes in flowing waters (Caissie, 2006). Primary research challenges in the field of river temperature include improving understanding of thermal heterogeneity at different spatial and temporal scales, the nature of past variability and likely future trends (Webb et al, 2008). The analysis of spatial and temporal variability in river temperature regimes is vital to (1) elucidate key controls and processes, (2) assess sensitivity to a changing climate and (3) inform management of land use, water resources and freshwater ecosystems (Moore et al, 2005). River temperature has attracted growing attention because water thermal. Drivers of river temperature dynamics are complex, with multivariate controls and process interactions spatially nested at macro (latitude, altitude and continentality), meso (basin climate and hydrology) and micro (micro-meteorology, channel geometry, riparian shading and substratum conditions) scales (Webb, 1996).

Objectives

Methods

Results

Discussion

Conclusion