A large-sample investigation into uncertain climate change impacts on high flows across Great Britain

[摘要] Climate change may significantly increase flood risk globally, but there arelarge uncertainties in both future climatic changes and how these propagateinto changing river flows. Here, the impact of climate change on themagnitude and frequency of high flows is analysed for Great Britain (GB) toprovide the first spatially consistent GB projections to include bothclimate ensembles and hydrological model parameter uncertainties. We use thelatest high-resolution (12 km) regional climate model ensemble from the UKClimate Projections (UKCP18). These projections are based on aperturbed-physics ensemble of 12 regional climate model simulations andallow exploration of climate model uncertainty beyond the variability causedby the use of different models. We model 346 larger ( > 144  km 2 ) catchments across GB using the DECIPHeR hydrological modellingframework. Generally, results indicated an increase in the magnitude andfrequency of high flows (Q10, Q1, and annual maximum) along the western coast of GB in the future (2050–2075), with increases in annual maximum flows of upto 65 % for western Scotland. In contrast, median flows (Q50) were projected to decrease across GB. Even when using an ensemble based on a single regional climate model (RCM) structure, all flow projections contained large uncertainties. While the RCMparameters were the largest source of uncertainty overall, hydrologicalmodelling uncertainties were considerable in eastern and south-eastern England. Regional variations in flow projections were found to relate to (i)differences in climatic change and (ii) catchment conditions during thebaseline period as characterised by the runoff coefficient (mean dischargedivided by mean precipitation). Importantly, increased heavy-precipitationevents (defined by an increase in 99th percentile precipitation) did notalways result in increased flood flows for catchments with low runoffcoefficients, highlighting the varying factors leading to changes in highflows. These results provide a national overview of climate change impactson high flows across GB, which will inform climate change adaptation, andhighlight the impact of hydrological model parameter uncertainties whenmodelling climate change impact on high flows.

[学科分类] 妇产科学