Defining high-flow seasons using temporal streamflow patterns from a global model
TL;DR: In this paper, a novel approach to defining high-flow seasons (3-month) globally is presented by identifying temporal patterns of streamflow using a volume-based threshold technique and the PCR-GLOBWB model.
Abstract: Globally, flood catastrophes lead all natural hazards in terms of impacts on society, causing billions of dollars of damages annually. Here, a novel approach to defining high-flow seasons (3-month) globally is presented by identifying temporal patterns of streamflow. The main high-flow season is identified using a volume-based threshold technique and the PCR-GLOBWB model. In comparison with observations, 40 % (50 %) of locations at a station (sub-basin) scale have identical peak months and 81 % (89 %) are within 1 month, indicating fair agreement between modeled and observed high-flow seasons. Minor high-flow seasons are also defined for bi-modal flow regimes. Identified major and minor high-flow seasons together are found to well represent actual flood records from the Dartmouth Flood Observatory, further substantiating the model's ability to reproduce the appropriate high-flow season. These high-spatial-resolution high-flow seasons and associated performance metrics allow for an improved understanding of temporal characterization of streamflow and flood potential, causation, and management. This is especially attractive for regions with limited observations and/or little capacity to develop early warning flood systems.
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TL;DR: In this article, the authors examine trends in streamflow events using 2776 stations from the Global Runoff Data Center, with events chosen to isolate the impact of changes to their respective rainfall and antecedent soil moisture.
60 citations
TL;DR: In this article, the authors investigate both the center timing of streamflow and the day of maximum flow using a local water year for each station, defined as the month of lowest average monthly streamflow This definition of water year prevents ambiguity in the direction of computed trends and enables flood and streamflow timing to be described by a normal distribution.
Abstract: Analysis of flood and streamflow timing has recently gained prominence as a tool for attribution of climatic changes to flooding Such studies generally apply circular statistics to the day of maximum flow in a calendar year and use nonparametric linear trend tests to investigate changes in flooding on a local or regional scale Here we investigate both the center timing of streamflow and the day of maximum flow using a local water year For each station, the start of the water year is defined as the month of lowest average monthly streamflow This definition of water year prevents ambiguity in the direction of computed trends and enables flood and streamflow timing to be described by a normal distribution Using the assumption of normality, we calculate the historical trend in both flood and streamflow timing using linear regression While shifts in flood and streamflow timing are consistent with climate change and are shifting in a similar direction, shifts in the timing of the annual maxima flood are approximately three times that of streamflow timing The results here have implications for water resources and environmental management where streamflow and flood timing are critical to planning The applicability of the normal approximation to flood and streamflow timing will enable future analyses to use parametric statistics
44 citations
Cites background or methods from "Defining high-flow seasons using te..."
...Mean flood timing calculated using the arithmetic mean of the ordinal day based on local water year (Equations 3 and 4) is presented in Figure 3b. Themean flood timing resembles similar global studies of high flow season (Lee et al., 2015) and peak flowmonth (Dettinger & Diaz, 2000)....
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...Data and Water Year Definition Daily streamflow from the Global Runoff Data Centre (GRDC, 2015) as successfully used in other global studies (Do et al., 2017; Lee et al., 2015; Milly et al., 2018; Wasko & Sharma, 2017; Wasko et al., 2019) was adopted here....
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...Although alternative definitions of streamflow timing exist (e.g., Lee et al., 2015), using the above center timing definition is attractive, as it provides an ordinal day, which is easily compared to the flood timing....
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38 citations
Cites background or methods or result from "Defining high-flow seasons using te..."
...To our knowledge, Lee et al. (2015) is the onlymodel‐based study to produce a global map of the peak flow season (defined as the consecutive 3‐month period with the highest number of events above a threshold of streamflow volume), whereas model‐based studies of timing of annual maximum streamflow…...
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...The prediction of flood timing not only has consistency with flood timing based on regional observational studies in Europe and North America but also has high consistency with the spatial patterns of the main high‐flow season obtained from a global hydrological model (Lee et al., 2015)....
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...The spatial pattern of flood seasons obtained from this analysis compares favorably to the high‐flow seasonal data obtained from a global hydrological model (Lee et al., 2015) and streamflow peak month obtained from 1,345 sites globally (Dettinger & Diaz, 2000) or the...
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...One possibility is to simulate runoff and extract information of flood timing through the use of global hydrological models (Lee et al., 2015) forced with global reanalysis climate....
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...…pattern of flood seasons obtained from this analysis compares favorably to the high‐flow seasonal data obtained from a global hydrological model (Lee et al., 2015) and streamflow peak month obtained from 1,345 sites globally (Dettinger & Diaz, 2000) or the recently published gridded runoff…...
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TL;DR: This article examined the influence of the Indian Ocean Dipole (IOD) and El Nino Southern Oscillation (ENSO) across sub-Saharan Africa, finding significant changes in flood timing between positive and negative phases of both IOD and ENSO.
Abstract: Modes of climate variability are known to influence rainy season onset, but there is less understanding of how they impact flood timing. We use streamflow reanalysis and gauged observation datasets to examine the influence of the Indian Ocean Dipole (IOD) and El Nino Southern Oscillation (ENSO) across sub-Saharan Africa. We find significant changes in flood timing between positive and negative phases of both IOD and ENSO; in some cases the difference in the timing of annual flood events is more than 3 months. Sensitivity to one or other mode of variability differs regionally. Changes in flood timing are larger than variability in rainy season onset reported in the literature, highlighting the need to understand how the hydrological system alters climate variability signals seen in rainy season onset, length and rainfall totals. Our insights into flood timing could support communities who rely on flood-based farming systems to adapt to climate variability.
34 citations
TL;DR: In this article, the authors attribute seasonal peak-flow to large-scale climate patterns, including the El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillations (PDO), North Atlantic Oscillant (NAO), and Atlantic Multidecadal Onto-Oscillation, using streamflow station observations and simulations from PCR-GLOBWB, a global-scale hydrologic model.
Abstract: Flood-related fatalities and impacts on society surpass those from all other natural disasters globally. While the inclusion of large-scale climate drivers in streamflow (or high-flow) prediction has been widely studied, an explicit link to global-scale long-lead prediction is lacking, which can lead to an improved understanding of potential flood propensity. Here we attribute seasonal peak-flow to large-scale climate patterns, including the El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), and Atlantic Multidecadal Oscillation (AMO), using streamflow station observations and simulations from PCR-GLOBWB, a global-scale hydrologic model. Statistically significantly correlated climate patterns and streamflow autocorrelation are subsequently applied as predictors to build a global-scale season-ahead prediction model, with prediction performance evaluated by the mean squared error skill score (MSESS) and the categorical Gerrity skill score (GSS). Globally, fair-to-good prediction skill (20% ≤ MSESS and 0.2 ≤ GSS) is evident for a number of locations (28% of stations and 29% of land area), most notably in data-poor regions (e.g., West and Central Africa). The persistence of such relevant climate patterns can improve understanding of the propensity for floods at the seasonal scale. The prediction approach developed here lays the groundwork for further improving local-scale seasonal peak-flow prediction by identifying relevant global-scale climate patterns. This is especially attractive for regions with limited observations and or little capacity to develop flood early warning systems.
30 citations
Cites methods from "Defining high-flow seasons using te..."
...Using PCR-GLOBWB streamflow time series globally, we follow an identical approach as with the GRDC observations to construct seasonal peak-flow, averaging streamflow in the predefined peak season (Lee et al., 2015) for each grid globally....
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...Peak-flow season defined using the volume-based threshold method with streamflow simulations from the PCR-GLOBWB model (Lee et al., 2015)....
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References
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European Centre for Medium-Range Weather Forecasts1, Lawrence Livermore National Laboratory2, Chinese Academy of Sciences3, Japan Meteorological Agency4, Met Office5, University of Reading6, Max Planck Society7, Royal Netherlands Meteorological Institute8, National Center for Atmospheric Research9, National Oceanic and Atmospheric Administration10
TL;DR: ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions as mentioned in this paper.
Abstract: ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instruments from the 1970s onwards, supplemented by increasing numbers of observations from aircraft, ocean-buoys and other surface platforms, but with a declining number of radiosonde ascents since the late 1980s. The observations used in ERA-40 were accumulated from many sources. The first part of this paper describes the data acquisition and the principal changes in data type and coverage over the period. It also describes the data assimilation system used for ERA-40. This benefited from many of the changes introduced into operational forecasting since the mid-1990s, when the systems used for the 15-year ECMWF re-analysis (ERA-15) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis were implemented. Several of the improvements are discussed. General aspects of the production of the analyses are also summarized.
A number of results indicative of the overall performance of the data assimilation system, and implicitly of the observing system, are presented and discussed. The comparison of background (short-range) forecasts and analyses with observations, the consistency of the global mass budget, the magnitude of differences between analysis and background fields and the accuracy of medium-range forecasts run from the ERA-40 analyses are illustrated. Several results demonstrate the marked improvement that was made to the observing system for the southern hemisphere in the 1970s, particularly towards the end of the decade. In contrast, the synoptic quality of the analysis for the northern hemisphere is sufficient to provide forecasts that remain skilful well into the medium range for all years. Two particular problems are also examined: excessive precipitation over tropical oceans and a too strong Brewer-Dobson circulation, both of which are pronounced in later years. Several other aspects of the quality of the re-analyses revealed by monitoring and validation studies are summarized. Expectations that the ‘second-generation’ ERA-40 re-analysis would provide products that are better than those from the firstgeneration ERA-15 and NCEP/NCAR re-analyses are found to have been met in most cases. © Royal Meteorological Society, 2005. The contributions of N. A. Rayner and R. W. Saunders are Crown copyright.
7,110 citations
TL;DR: This work shows that an ensemble of 12 climate models exhibits qualitative and statistically significant skill in simulating observed regional patterns of twentieth-century multidecadal changes in streamflow, and projects changes in sustainable water availability by the year 2050.
Abstract: Water availability on the continents is important for human health, economic activity, ecosystem function and geophysical processes. Because the saturation vapour pressure of water in air is highly sensitive to temperature, perturbations in the global water cycle are expected to accompany climate warming. Regional patterns of warming-induced changes in surface hydroclimate are complex and less certain than those in temperature, however, with both regional increases and decreases expected in precipitation and runoff. Here we show that an ensemble of 12 climate models exhibits qualitative and statistically significant skill in simulating observed regional patterns of twentieth-century multidecadal changes in streamflow. These models project 10-40% increases in runoff in eastern equatorial Africa, the La Plata basin and high-latitude North America and Eurasia, and 10-30% decreases in runoff in southern Africa, southern Europe, the Middle East and mid-latitude western North America by the year 2050. Such changes in sustainable water availability would have considerable regional-scale consequences for economies as well as ecosystems.
2,059 citations
"Defining high-flow seasons using te..." refers background in this paper
..., 2006; Probst and Tardy, 1987) and modeled streamflow from global hydrological models (Beck et al., 2015; van Dijk et al., 2013; McCabe and Wolock, 2008; Milly et al., 2005; Ward et al., 2013, 2014) to investigate ungauged and poorly gauged basins (Fekete and Vörösmarty, 2007)....
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...…2004; Poff et al., 2006; Probst and Tardy, 1987) and modeled streamflow from global hydrological models (Beck et al., 2015; van Dijk et al., 2013; McCabe and Wolock, 2008; Milly et al., 2005; Ward et al., 2013, 2014) to investigate ungauged and poorly gauged basins (Fekete and Vörösmarty, 2007)....
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McGill University1, University of Washington2, The Nature Conservancy3, City University of New York4, European Environment Agency5, Goethe University Frankfurt6, Food and Agriculture Organization7, University of Yamanashi8, Umeå University9, University of Greifswald10, World Wide Fund for Nature11, University of New Hampshire12
TL;DR: Despite the recognized importance of reservoirs and dams, global datasets describing their characteristics and geographical distribution are largely incomplete as mentioned in this paper, which makes it difficult to perform advanced assessments of dams and reservoirs.
Abstract: Despite the recognized importance of reservoirs and dams, global datasets describing their characteristics and geographical distribution are largely incomplete. To enable advanced assessments of th ...
1,493 citations
TL;DR: In this article, the Mann-Kendall nonparametric test was used to detect trends in hydrologic variables and a permutation approach to estimate the test distribution, and accounts for the correlation structure in the data in determining the significance level of the test results.
1,019 citations
TL;DR: The WATCH Forcing Data for 1958-2001 based on the 40-yr ECMWF Re-Analysis (ERA-40) and for 1901-57 based on reordered reanalysis data as mentioned in this paper.
Abstract: The Water and Global Change (WATCH) project evaluation of the terrestrial water cycle involves using land surface models and general hydrological models to assess hydrologically important variables including evaporation, soil moisture, and runoff. Such models require meteorological forcing data, and this paper describes the creation of the WATCH Forcing Data for 1958–2001 based on the 40-yr ECMWF Re-Analysis (ERA-40) and for 1901–57 based on reordered reanalysis data. It also discusses and analyses model-independent estimates of reference crop evaporation. Global average annual cumulative reference crop evaporation was selected as a widely adopted measure of potential evapotranspiration. It exhibits no significant trend from 1979 to 2001 although there are significant long-term increases in global average vapor pressure deficit and concurrent significant decreases in global average net radiation and wind speed. The near-constant global average of annual reference crop evaporation in the late twentieth century masks significant decreases in some regions (e.g., the Murray–Darling basin) with significant increases in others.
797 citations