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Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrology".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 40152

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Special Issue Editors

Dr. Rajesh R. Shrestha

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Guest Editor

Research Scientist, Environment and Climate Change Canada, Watershed Hydrology and Ecology Research Division, University of Victoria, Victoria, BC V8P 5C2, Canada
Interests: climate change impacts; water resources; watershed hydrology; hydro-climatology; hydrologic modelling; hydrologic extremes; statistical and machine learning methods
Special Issues, Collections and Topics in MDPI journals

Dr. Mohammad Reza Najafi

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Guest Editor

Department of Civil and Environmental Engineering, Western University, Ontario, ON N6A 3K7, Canada
Interests: watershed hydrology; hydroclimatic extremes; climate change impact assessment; detection and attribution; infrastructure risk and resilience; regional frequency analysis; multi-modeling and uncertainty assessment; downscaling and bias correction
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Climate change induced intensification of the global water cycle is impacting the frequency and severity of hydrologic extremes, including floods and droughts. Future changes in the magnitude, intensity, frequency and seasonality of precipitation, increased evapotranspiration, and shifts from snow towards rainfall regimes can further exacerbate the flood and drought risks in many regions of the world. Furthermore, there are indications that rain-on-snow and atmospheric river driven flood events will intensify in the future climate. These climate induced changes coupled with direct human impacts, such as floodplain development and land use change, could lead to severe natural disasters. Thus, understanding the historical and future trajectories of hydrologic extremes is crucial for water-resources risk assessment and planning. In this context, the nonstationarity of hydrologic extremes is highly relevant, as it could significantly alter the frequency distribution of extreme events. However, the application of nonstationary methods pose a number of challenges, such as selecting an appropriate modelling strategy, handling uncertainties, and understanding and communicating the associated concepts and risks. This special issue will provide a platform for research that will assess the impacts of historical and projected climate change on hydrologic extremes. We seek both application studies and methodological studies that focus on hydrological extremes (peak- and low-flows) and associated risks (floods, droughts). The topics covered by this special Issue will include but not limited to the following:

Analysis of historical variability and trends in streamflow extremes (e.g., peak flow, low flow, timing) and teleconnections to hydroclimatic drivers
Model based studies on future changes in hydrologic extremes and the role of internal variability and anthropogenic forcings
Development and application of nonstationary methods for the evaluation of hydrologic extreme events
Evaluation of uncertainties of extreme value projections
Methods to quantify flood and drought risks
Implications of changes in hydrologic extreme events on water resources management

Dr. Rajesh R. Shrestha
Dr. Mohammad Reza Najafi
Guest Editors

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Keywords

Hydrologic trends
Peak flow
Low flow
Flood
Drought
Climate change
Nonstationarity
Uncertainty analysis
Extreme value analysis

Published Papers (12 papers)

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Editorial

Jump to: Research

5 pages, 188 KiB

Open AccessEditorial

Special Issue: Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts

by Rajesh R. Shrestha and Mohammad Reza Najafi

Water 2022, 14(10), 1658; https://doi.org/10.3390/w14101658 - 23 May 2022

Viewed by 2033

Abstract

The intensification of global water cycle, associated with anthropogenic climate change, is affecting the characteristics of hydrologic extreme events throughout the world [...] Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

Research

Jump to: Editorial

15 pages, 23241 KiB

Open AccessFeature PaperArticle

Contribution of Glacier Runoff during Heat Waves in the Nooksack River Basin USA

by Mauri S. Pelto, Mariama Dryak, Jill Pelto, Tom Matthews and L. Baker Perry

Water 2022, 14(7), 1145; https://doi.org/10.3390/w14071145 - 02 Apr 2022

Cited by 12 | Viewed by 3695

Abstract

The thirty-eight-year record (1984–2021) of glacier mass balance measurement indicates a significant glacier response to climate change in the North Cascades, Washington that has led to declining glacier runoff in the Nooksack Basin. Glacier runoff in the Nooksack Basin is a major source of streamflow during the summer low-flow season and mitigates both low flow and warm water temperatures; this is particularly true during summer heat waves. Synchronous observations of glacier ablation and stream discharge immediately below Sholes Glacier from 2013–2017, independently identify daily discharge during the ablation season. The identified ablation rate is applied to glaciers across the North Fork Nooksack watershed, providing daily glacier runoff discharge to the North Fork Nooksack River. This is compared to observed daily discharge and temperature data of the North Fork Nooksack River and the unglaciated South Fork Nooksack River from the USGS. The ameliorating role of glacier runoff on discharge and water temperature is examined during 24 late summer heat wave events from 2010–2021. The primary response to these events is increased discharge in the heavily glaciated North Fork, and increased stream temperature in the unglaciated South Fork. During the 24 heat events, the discharge increased an average of +24% (±17%) in the North Fork and decreased an average of 20% (±8%) in the South Fork. For water temperature the mean increase was 0.7 °C (±0.4 °C) in the North Fork and 2.1 °C (±1.2 °C) in the South Fork. For the North Fork glacier runoff production was equivalent to 34% of the total discharge during the 24 events. Ongoing climate change will likely cause further decreases in summer baseflow and summer baseflow, along with an increase in water temperature potentially exceeding tolerance levels of several Pacific salmonid species that would further stress this population. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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24 pages, 5033 KiB

Open AccessArticle

Nonstationary Design Flood Estimation in Response to Climate Change, Population Growth and Cascade Reservoir Regulation

by Yuzuo Xie, Shenglian Guo, Lihua Xiong, Jing Tian and Feng Xiong

Water 2021, 13(19), 2687; https://doi.org/10.3390/w13192687 - 28 Sep 2021

Cited by 4 | Viewed by 1779

Abstract

The hydrologic data series are nonstationary due to climate change and local anthropogenic activities. The existing nonstationary design flood estimation methods usually focus on the statistical nonstationarity of the flow data series in the catchment, which neglect the hydraulic approach, such as reservoir flood regulation. In this paper, a novel approach to comprehensively consider the driving factors of non-stationarities in design flood estimation is proposed, which involves three main steps: (1) implementation of the candidate predictors with trend tests and change point detection for preliminary analysis; (2) application of the nonstationary flood frequency analysis with the principle of Equivalent Reliability (ER) for design flood volumes; (3) development of a nonstationary most likely regional composition (NS-MLRC) method, and the estimation of a design flood hydrograph at downstream cascade reservoirs. The proposed framework is applied to the cascade reservoirs in the Han River, China. The results imply that: (1) the NS-MLRC method provides a much better explanation for the nonstationary spatial correlation of the flood events in Han River basin, and the multiple nonstationary driving forces can be precisely quantified by the proposed design flood estimation framework; (2) the impacts of climate change and population growth are long-lasting processes with significant risk of flood events compared with stationary distribution conditions; and (3) the swift effects of cascade reservoirs are reflected in design flood hydrographs with lower peaks and lesser volumes. This study can provide a more integrated template for downstream flood risk management under the impact of climate change and human activities. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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16 pages, 4905 KiB

Open AccessArticle

Multiple Indicators of Extreme Changes in Snow-Dominated Streamflow Regimes, Yakima River Basin Region, USA

by Anna M. Wagner, Katrina E. Bennett, Glen E. Liston, Christopher A. Hiemstra and Dan Cooley

Water 2021, 13(19), 2608; https://doi.org/10.3390/w13192608 - 22 Sep 2021

Cited by 8 | Viewed by 1936

Abstract

Snow plays a major role in the hydrological cycle. Variations in snow duration and timing can have a negative impact on water resources. Excluding predicted changes in snowmelt rates and amounts could result in deleterious infrastructure, military mission, and asset impacts at military bases across the US. A change in snowpack can also lead to water shortages, which in turn can affect the availability of irrigation water. We performed trend analyses of air temperature, snow water equivalent (SWE) at 22 SNOTEL stations, and streamflow extremes for selected rivers in the snow-dependent and heavily irrigated Yakima River Basin (YRB) located in the Pacific Northwest US. There was a clear trend of increasing air temperature in this study area over a 30 year period (water years 1991–2020). All stations indicated an increase in average air temperatures for December (0.97 °C/decade) and January (1.12 °C/decade). There was also an upward trend at most stations in February (0.28 °C/decade). In December–February, the average air temperatures were 0.82 °C/decade. From these trends, we estimate that, by 2060, the average air temperatures for December–February at most (82%) stations will be above freezing. Furthermore, analysis of SWE from selected SNOTEL stations indicated a decreasing trend in historical SWE, and a shift to an earlier peak SWE was also assumed to be occurring due of the shorter snow duration. Decreasing trends in snow duration, rain-on-snow, and snowmelt runoff also resulted from snow modeling simulations of the YRB and the nearby area. We also observed a shift in the timing of snowmelt-driven peak streamflow, as well as a statistically significant increase in winter maximum streamflow and decrease in summer maximum and minimum streamflow trends by 2099. From the streamflow trends and complementary GEV analysis, we show that the YRB basin is a system in transition with earlier peak flows, lower snow-driven maximum streamflow, and higher rainfall-driven summer streamflow. This study highlights the importance of looking at changes in snow across multiple indicators to develop future infrastructure and planning tools to better adapt and mitigate changes in extreme events. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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26 pages, 4300 KiB

Open AccessArticle

Uncertainties in Riverine and Coastal Flood Impacts under Climate Change

by Shuyi Wang, Mohammad Reza Najafi, Alex J. Cannon and Amir Ali Khan

Water 2021, 13(13), 1774; https://doi.org/10.3390/w13131774 - 27 Jun 2021

Cited by 11 | Viewed by 3435

Abstract

Climate change can affect different drivers of flooding in low-lying coastal areas of the world, challenging the design and planning of communities and infrastructure. The concurrent occurrence of multiple flood drivers such as high river flows and extreme sea levels can aggravate such impacts and result in catastrophic damages. In this study, the individual and compound effects of riverine and coastal flooding are investigated at Stephenville Crossing located in the coastal-estuarine region of Newfoundland and Labrador (NL), Canada. The impacts of climate change on flood extents and depths and the uncertainties associated with temporal patterns of storms, intensity–duration–frequency (IDF) projections, spatial resolution, and emission scenarios are assessed. A hydrologic model and a 2D hydraulic model are set up and calibrated to simulate the flood inundation for the historical (1976–2005) as well as the near future (2041–2070) and far future (2071–2100) periods under Representative Concentration Pathways (RCPs) 4.5 and 8.5. Future storm events are generated based on projected IDF curves from convection-permitting Weather Research and Forecasting (WRF) climate model simulations, using SCS, Huff, and alternating block design storm methods. The results are compared with simulations based on projected IDF curves derived from statistically downscaled Global Climate Models (GCMs). Both drivers of flooding are projected to intensify in the future, resulting in higher risks of flooding in the study area. Compound riverine and coastal flooding results in more severe inundation, affecting the communities on the coastline and the estuary area. Results show that the uncertainties associated with storm hyetographs are considerable, which indicate the importance of accurate representation of storm patterns. Further, simulations based on projected WRF-IDF curves show higher risks of flooding compared to the ones associated with GCM-IDFs. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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17 pages, 7497 KiB

Open AccessFeature PaperArticle

Assessing Climatic Drivers of Spring Mean and Annual Maximum Flows in Western Canadian River Basins

by Yonas B. Dibike, Rajesh R. Shrestha, Colin Johnson, Barrie Bonsal and Paulin Coulibaly

Water 2021, 13(12), 1617; https://doi.org/10.3390/w13121617 - 08 Jun 2021

Cited by 6 | Viewed by 2022

Abstract

Flows originating from cold and mountainous watersheds are highly dependent on temperature and precipitation patterns, and the resulting snow accumulation and melt conditions, affecting the magnitude and timing of annual peak flows. This study applied a multiple linear regression (MLR) modelling framework to investigate spatial variations and relative importance of hydroclimatic drivers of annual maximum flows (AMF) and mean spring flows (MAMJflow) in 25 river basins across western Canada. The results show that basin average maximum snow water equivalent (SWEmax), April 1st SWE and spring precipitation (MAMJprc) are the most important predictors of both AMF and MAMJflow, with the proportion of explained variance averaging 51.7%, 44.0% and 33.5%, respectively. The MLR models’ abilities to project future changes in AMF and MAMJflow in response to changes to the hydroclimatic controls are also examined using the Canadian Regional Climate Model (CanRCM4) output for RCP 4.5 and RCP8.5 scenarios. The results show considerable spatial variations depending on individual watershed characteristics with projected changes in AMF ranging from −69% to +126% and those of MAMJflow ranging from −48% to +81% by the end of this century. In general, the study demonstrates that the MLR framework is a useful approach for assessing the spatial variation in hydroclimatic controls of annual maximum and mean spring flows in the western Canadian river basins. However, there is a need to exercise caution in applying MLR models for projecting changes in future flows, especially for regulated basins. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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20 pages, 3466 KiB

Open AccessEditor’s ChoiceArticle

Hydrological Extremes and Responses to Climate Change in the Kelantan River Basin, Malaysia, Based on the CMIP6 HighResMIP Experiments

by Mou Leong Tan, Ju Liang, Narimah Samat, Ngai Weng Chan, James M. Haywood and Kevin Hodges

Water 2021, 13(11), 1472; https://doi.org/10.3390/w13111472 - 24 May 2021

Cited by 28 | Viewed by 5780

Abstract

This study introduces a hydro-climatic extremes assessment framework that combines the latest climate simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) HighResMIP with the Soil and Water Assessment (SWAT) model, and examines the influence of the different climate model resolutions. Sixty-six hydrological and environmental flow indicators from the Indicators of Hydrologic Alteration (IHA) were computed to assess future extreme flows in the Kelantan River Basin (KRB), Malaysia, which is particularly vulnerable to flooding. Results show that the annual precipitation, streamflow, maximum and minimum temperatures are projected to increase by 6.9%, 9.9%, 0.8 °C and 0.9 °C, respectively, by the 2021–2050 period relative to the 1985–2014 baseline. Monthly precipitation and streamflow are projected to increase especially for the Southwest Monsoon (June–September) and the early phase of the Northeast Monsoon (December) periods. The magnitudes of the 1-, 3-, 7-, 30- and 90-day minima flows are projected to increase by 7.2% to 8.2% and the maxima flows by 10.4% to 28.4%, respectively. Lastly, changes in future hydro-climatic extremes are frequently quite different between the high-resolution and low-resolution models, e.g., the high-resolution models projected an increase of 11.8% in mean monthly flow in November-December-January compared to 3.2% for the low-resolution models. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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25 pages, 4761 KiB

Open AccessArticle

The Impact of the Uncertain Input Data of Multi-Purpose Reservoir Volumes under Hydrological Extremes

by Stanislav Paseka and Daniel Marton

Water 2021, 13(10), 1389; https://doi.org/10.3390/w13101389 - 16 May 2021

Cited by 3 | Viewed by 2003

Abstract

The topic of uncertainties in water management tasks is a very extensive and highly discussed one. It is generally based on the theory that uncertainties comprise epistemic uncertainty and aleatoric uncertainty. This work deals with the comprehensive determination of the functional water volumes of a reservoir during extreme hydrological events under conditions of aleatoric uncertainty described as input data uncertainties. In this case, the input data uncertainties were constructed using the Monte Carlo method and applied to the data employed in the water management solution of the reservoir: (i) average monthly water inflows, (ii) hydrographs, (iii) bathygraphic curves and (iv) water losses by evaporation and dam seepage. To determine the storage volume of the reservoir, a simulation-optimization model of the reservoir was developed, which uses the balance equation of the reservoir to determine its optimal storage volume. For the second hydrological extreme, a simulation model for the transformation of flood discharges was developed, which works on the principle of the first order of the reservoir differential equation. By linking the two models, it is possible to comprehensively determine the functional volumes of the reservoir in terms of input data uncertainties. The practical application of the models was applied to a case study of the Vír reservoir in the Czech Republic, which fulfils the purpose of water storage and flood protection. The obtained results were analyzed in detail to verify whether the reservoir is sufficiently resistant to current hydrological extremes and also to suggest a redistribution of functional volumes of the reservoir under conditions of measurement uncertainty. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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19 pages, 56016 KiB

Open AccessFeature PaperArticle

Concurrent Changes in Extreme Hydroclimate Events in the Colorado River Basin

by Katrina E. Bennett, Carl Talsma and Riccardo Boero

Water 2021, 13(7), 978; https://doi.org/10.3390/w13070978 - 01 Apr 2021

Cited by 7 | Viewed by 5856

Abstract

Extreme events resulting in catastrophic damage have more than doubled in the last five years, costing hundreds of lives and thousands of homes, and heavily undermining regional economic stability. At present, most of these hydroclimatic extreme events are documented by the media as individual events; however, in scientific terms, many are better understood as concurrent events—concurrent extremes of both temperature and precipitation (e.g., drought, floods). This paper considers concurrent changes in hydroclimate extremes, including heatwaves, drought, flooding, and low flows, in six historical-to-future (1970–1999, 2070–2099) Earth System Model (ESM) climate scenarios for the Colorado River basin. Results indicate that temperature-driven Impacts (heatwaves, drought) have the strongest responses while precipitation-driven Impacts have weaker responses. All Impacts exhibit an increase in magnitude from synoptic to annual time scales, with heatwaves increasing in strength about three times at the annual time scale versus the synoptic, while low flows only increase slightly. Critical watersheds in the Colorado were identified, highlighting the Blue River basin, Uncompahgre, East Taylor, Salt/Verde watersheds, locations of important water infrastructures, water resources, and hydrological research. Our results indicate that concurrent extreme hydroclimate events are projected to increase in the future and intensify within critical regions of the Colorado River basin. Considering extreme hydroclimate events concurrently is an important step towards linking economic and social effects of these events and their associated instabilities on a regional scale. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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19 pages, 5870 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Climatic Controls on Mean and Extreme Streamflow Changes Across the Permafrost Region of Canada

by Rajesh R. Shrestha, Jennifer Pesklevits, Daqing Yang, Daniel L. Peters and Yonas B. Dibike

Water 2021, 13(5), 626; https://doi.org/10.3390/w13050626 - 27 Feb 2021

Cited by 7 | Viewed by 2619

Abstract

Climatic change is affecting streamflow regimes of the permafrost region, altering mean and extreme streamflow conditions. In this study, we analyzed historical trends in annual mean flow (Q_mean), minimum flow (Q_min), maximum flow (Q_max) and Q_max timing across 84 hydrometric stations in the permafrost region of Canada. Furthermore, we related streamflow trends with temperature and precipitation trends, and used a multiple linear regression (MLR) framework to evaluate climatic controls on streamflow components. The results revealed spatially varied trends across the region, with significantly increasing (at 10% level) Q_min for 43% of stations as the most prominent trend, and a relatively smaller number of stations with significant Q_mean, Q_max and Q_max timing trends. Temperatures over both the cold and warm seasons showed significant warming for >70% of basin areas upstream of the hydrometric stations, while precipitation exhibited increases for >15% of the basins. Comparisons of the 1976 to 2005 basin-averaged climatological means of streamflow variables with precipitation and temperature revealed a positive correlation between Q_mean and seasonal precipitation, and a negative correlation between Q_mean and seasonal temperature. The basin-averaged streamflow, precipitation and temperature trends showed weak correlations that included a positive correlation between Q_min and October to March precipitation trends, and negative correlations of Q_max timing with October to March and April to September temperature trends. The MLR-based variable importance analysis revealed the dominant controls of precipitation on Q_mean and Q_max, and temperature on Q_min. Overall, this study contributes towards an enhanced understanding of ongoing changes in streamflow regimes and their climatic controls across the Canadian permafrost region, which could be generalized for the broader pan-Arctic regions. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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27 pages, 6564 KiB

Open AccessEditor’s ChoiceArticle

Impact of Climate Change on Precipitation Extremes over Ho Chi Minh City, Vietnam

by Dao Nguyen Khoi, Nguyen Trong Quan, Pham Thi Thao Nhi and Van Thinh Nguyen

Water 2021, 13(2), 120; https://doi.org/10.3390/w13020120 - 07 Jan 2021

Cited by 9 | Viewed by 4511

Abstract

In the context of climate change, the impact of hydro-meteorological extremes, such as floods and droughts, has become one of the most severe issues for the governors of mega-cities. The main purpose of this study is to assess the spatiotemporal changes in extreme precipitation indices over Ho Chi Minh City, Vietnam, between the near (2021–2050) and intermediate (2051–2080) future periods with respect to the baseline period (1980–2009). The historical extreme indices were calculated through observed daily rainfall data at 11 selected meteorological stations across the study area. The future extreme indices were projected based on a stochastic weather generator, the Long Ashton Research Station Weather Generator (LARS-WG), which incorporates climate projections from the Coupled Model Intercomparison Project 5 (CMIP5) ensemble. Eight extreme precipitation indices, such as the consecutive dry days (CDDs), consecutive wet days (CWDs), number of very heavy precipitation days (R20mm), number of extremely heavy precipitation days (R25mm), maximum 1 d precipitation amount (RX1day), maximum 5 d precipitation amount (RX5day), very wet days (R95p), and simple daily intensity index (SDII) were selected to evaluate the multi-model ensemble mean changes of extreme indices in terms of intensity, duration, and frequency. The statistical significance, stability, and averaged magnitude of trends in these changes, thereby, were computed by the Mann-Kendall statistical techniques and Sen’s estimator, and applied to each extreme index. The results indicated a general increasing trend in most extreme indices for the future periods. In comparison with the near future period (2021–2050), the extreme intensity and frequency indices in the intermediate future period (2051–2080) present more statistically significant trends and higher growing rates. Furthermore, an increase in most extreme indices mainly occurs in some parts of the central and southern regions, while a decrease in those indices is often projected in the north of the study area. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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24 pages, 3434 KiB

Open AccessArticle

Investigation of Attributes for Identifying Homogeneous Flood Regions for Regional Flood Frequency Analysis in Canada

by Ziyang Zhang and Tricia A. Stadnyk

Water 2020, 12(9), 2570; https://doi.org/10.3390/w12092570 - 15 Sep 2020

Cited by 8 | Viewed by 2637

Abstract

The identification of homogeneous flood regions is essential for regional flood frequency analysis. Despite the type of regionalization framework considered (e.g., region of influence or hierarchical clustering), selecting flood-related attributes to reflect flood generating mechanisms is required to discriminate flood regimes among catchments. To understand how different attributes perform across Canada for identifying homogeneous regions, this study examines five distinctive attributes (i.e., geographical proximity, flood seasonality, physiographic variables, monthly precipitation pattern, and monthly temperature pattern) for their ability to identify homogeneous regions at 186 gauging sites with their annual maximum flow data. We propose a novel region revision procedure to complement the well-known region of influence and L-Moments techniques that automates the identification of homogeneous regions across continental domains. Results are presented spatially for Canada to assess patterning of homogeneous regions. Memberships of two selected regions are investigated to provide insight into membership characteristics. Sites in eastern Canada are highly likely to identify homogeneous flood regions, while the western prairie and mountainous regions are not. Overall, it is revealed that the success of identifying homogeneous regions depends on local hydrological complexities, whether the considered attribute(s) reflect primary flooding mechanism(s), and on whether catchment sites are clustered in a small geographic region. Formation of effective pooling groups affords the extension of record lengths across the Canadian domain (where gauges typically have <50 years of record), facilitating more comprehensive analysis of higher return period flood needs for climate change assessment. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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