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Detection of long-term regional hydrological change from reference hydrometric networks in the UK and Europe

Hannaford, Jamie. 2011 Detection of long-term regional hydrological change from reference hydrometric networks in the UK and Europe. [Keynote] In: American Geophysical Union Fall Meeting December 2011, San Francisco, USA, 5-9 December 2011.

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Abstract/Summary

Reference hydrometric networks, consisting of near-natural catchments gauged by stations with good hydrometric performance, are increasingly being used by researchers in order to discern natural, climate-driven trends from other, more direct, anthropogenic disturbances (e.g. water abstraction and reservoir influences). In the UK, a “Benchmark” network has been designated, and has formed the core of a number of assessments of hydrological change. The Benchmark network has also been integrated into a pan-European network of reference catchments which has recently been used to characterize hydrological trends on a European scale. Whilst reference networks provide a natural flow response, they have a number of limitations. Reference networks are dominated by small (<1000 km2) headwater catchments – a necessary response to the need for an undisturbed flow condition – which are sparsely distributed, particularly in Europe, where human impacts on flow regimes are pervasive and issues of data sharing limit coverage. Flow records from reference catchments are typically short (from the 1960s – present), as catchments with long streamflow records tend to be vulnerable to inhomogeneities (e.g. due to changing gauging practices over time). However, there is a danger that results from short, fixed study periods may not be representative of long-term variability. There is, therefore, a fundamental mismatch between the spatial scale and temporal coverage offered by reference networks, and the scales required by policymakers in formulating responses to climate-driven hydrological change This presentation draws upon a range of recent research to provide a synthesis of key findings from studies of reference networks in the UK and Europe, with a particular focus on how data from networks of distributed catchments can be used to examine large-scale hydrological changes. The presentation illustrates some of the key methodological challenges associated with the analysis of reference networks, and will consider methods for overcoming limited spatial and temporal domain coverage in order to infer long-term hydrological variability at the regional, national, and continental scales. In addressing spatial coverage, approaches for reconciling small-scale observations with larger scales are considered, e.g. using large-scale hydrological models to provide estimates of change in ungauged areas. In addressing temporal coverage, the emphasis will be on methods which dispense with fixed study periods and thereby allow inter-decadal variabilty to be characterized, whilst consideration will be given to reconciling results from reference catchments with longer (albeit less reliable) records which provide proxies of change over timescales of a century or greater. This presentation reinforces the importance of reference networks in facilitating the identification and attribution of climate-driven trends. The inherent limitations of spatial and temporal coverage, a function of the exacting requirements of such networks, requires novel methodologies to provide a wider context; which, in the long-term, should lead to greater reconciliation between observations of change and projections from models, and improved knowledge of the magnitude and pace of regional hydrological change.

Item Type: Publication - Conference Item (Keynote)
Programmes: CEH Topics & Objectives 2009 onwards > Water > WA Topic 1 - Variability and Change in Water Systems > WA - 1.2 - Quantify variability and departures from natural historical variability in water quality ...
CEH Topics & Objectives 2009 onwards > Water > WA Topic 1 - Variability and Change in Water Systems > WA - 1.4 - Management and dissemination of freshwaters data
CEH Sections: Boorman
NORA Subject Terms: Meteorology and Climatology
Hydrology
Related URLs:
Date made live: 30 Jan 2012 12:01
URI: http://nora.nerc.ac.uk/id/eprint/16512

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