Assessment of Climate Change Impacts on Extreme High and Low Flows: An Improved Bottom-Up Approach

Abstract

A quantitative assessment of the likelihood of all possible future states is lacking in both the traditional top-down and the alternative bottom-up approaches to the assessment of climate change impacts. The issue is tackled herein by generating a large number of representative climate projections using weather generators calibrated with the outputs of regional climate models. A case study was performed on the South Nation River Watershed located in Eastern Ontario, Canada, using climate projections generated by four climate models and forced with medium- to high-emission scenarios (RCP4.5 and RCP8.5) for the future 30-year period (2071–2100). These raw projections were corrected using two downscaling techniques. Large ensembles of future series were created by perturbing downscaled data with a stochastic weather generator, then used as inputs to a hydrological model that was calibrated using observed data. Risk indices calculated with the simulated streamflow data were converted into probability distributions using Kernel Density Estimations. The results are dimensional joint probability distributions of risk-relevant indices that provide estimates of the likelihood of unwanted events under a given watershed configuration and management policy. The proposed approach offers a more complete vision of the impacts of climate change and opens the door to a more objective assessment of adaptation strategies.

Climate Change Impacts on Extreme Flows Under IPCC RCP Scenarios in the Mountainous Kaidu Watershed, Tarim River Basin

“…Previous studies have shown that, hydrological processes of several main basins in Tianshan and Kunlun Mountains have been significantly influenced by climate change [4]. Extreme precipitation events have the potential to aggravate floods and droughts [5][6][7], while the continuous rise in air/surface temperature may lead to the increasing snow melting and evapotranspiration (ET) in such mountainous river basins [8]. Understanding variations in historical discharge extremes and evaluating future changes will greatly contribute to flood hazard control and water resource management in inland river basins [9,10].…”

Extreme Floods and Droughts under Future Climate Scenarios

“…Papers [13,14] reported research on droughts. Future droughts under a range of climate scenarios were examined in [13].…”

“…This research identified the season, direction, and magnitude of changes in the length of dry spells for different parts of the Southeast United States. The effects of droughts on both low flows and floods were reported in [14]. This paper presented a novel method to create a super-ensemble of future climate series, which was then used to derive flooding and drought indices.…”

An open workflow for the study of unseen weather extremes

“…Instrumental records are typically only a few decades long and are not available everywhere (e.g. Alexander, 2016). Reanalysis products are increasingly employed to estimate extremes, as they blend observational datasets with model simulations into spatially and temporally coherent outputs, i.e., 'maps without gaps ' (e.g.…”