National-scale analysis of low flow frequency: historical trends and potential future changes

Abstract

Article (refereed) -postprint Kay, A.L.; Bell, V.A.; Guillod, B.P.; Jones, R.G.; Rudd, A.C. 2018. Nationalscale analysis of low flow frequency: historical trends and potential future changes. Climatic Change, 147 (3-4). 585-599. AbstractThe potential impact of climate change on hydrological extremes is of increasing concern across the globe. Here a national-scale grid-based hydrological model is used to investigate historical trends and potential future changes in low flow frequency across Great Britain. The historical analyses use both observational data and ensemble data from a regional climate model . The results show relatively few significant trends in historical low flows (2-or 20-year return period), whether based on 7-day or 30-day annual minima. Significant negative trends seen in some limited parts of the country when using observational data are generally not seen when using climate model data. The future analyses use climate model ensemble data for both near-future and far-future timeperiods (2020-2049 and 2070-2099 respectively), which are compared to a baseline sub-period from the historical ensemble . The results show future reductions in low flows, which are generally larger in the south of the country, at the higher (20-year) return period, and for the later time-period. Reductions are more limited if the estimates of future potential evaporation include the effect of increased carbon dioxide concentrations on stomatal resistance. Such reductions in river flow could have significant impacts on the aquatic environment and on agriculture, and present a challenge for water managers, especially as reductions in water supply are likely to occur alongside increases in demand.

An assessment of the potential for natural flood management to offset climate change impacts

“…NFM planning should also consider potential effects on low flows/droughts, which are themselves expected to worsen under climate change (e.g. Kay et al 2018). While there are limitations to the evidence presented here, this paper presents a novel method for evaluating the potential of NFM to offset the impacts of climate change on peak flows, and when the evidence base is enhanced a more robust assessment will be possible.…”

Added Value of Large Ensemble Simulations for Assessing Extreme River Discharge in a 2 °C Warmer World

“…The lack of full water system closure may introduce biases in future projections of drought, most notably due to the off-line computation of potential 10.1029/2019GL081967 evapotranspiration (Kay et al, 2018;Milly & Dunne, 2017). The lack of full water system closure may introduce biases in future projections of drought, most notably due to the off-line computation of potential 10.1029/2019GL081967 evapotranspiration (Kay et al, 2018;Milly & Dunne, 2017).…”

A Probabilistic Risk Assessment of the National Economic Impacts of Regulatory Drought Management on Irrigated Agriculture

“…However, this reform might also enforce more restrictive low flow conditions during drought than those presented here, in which river flow triggers are based on a historical monthly varying threshold of the low river flow conditions from a baseline period. As highlighted in previous studies (Kay et al, ), reductions in river flows are expected in the future. In contrast to this conventional variable threshold approach in which the thresholds do not adjust to the hydrological consequences of a changing climate, Wanders et al () applied a nonstationary transient variable threshold in which the threshold is based on the river flow of the previous 30 years.…”

“…G2G has been shown to perform well for a wide variety of catchments across Britain (Bell et al, ) and has recently been shown to perform well specifically for low flows and for historical drought identification (Rudd et al, ). The weather@home2 hydrological data set has been used to analyze potential future changes in low flows and drought characteristics (Kay et al, ).…”