Identifying Spatial Patterns of Hydrologic Drought over the Southeast US Using Retrospective National Water Model Simulations

Dyer, Jamie; Mercer, Andrew E.; Raczyński, Krzysztof

doi:10.3390/w14101525

Cited by 10 publications

(5 citation statements)

References 28 publications

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“…This indicates good agreement of the model data to real conditions. Some studies suggest the inclusion of at least fourth-order nodes in the analysis, due to lower NWM performance in lower-order nodes (Dyer et al, 2022;; however, results from this work indicate that third-order nodes are not significantly different from higher order nodes in terms of spatial and temporal patterns. As indicated by , NWM data-driven approaches might not be highly accurate in terms of point-to-point data values, but perform well in highlighting the regions likely to be at risk of high magnitude streamflow event occurrence.…”

Section: Trendscontrasting

confidence: 59%

Quantifying patterns of streamflow peaks over the southeastern United States using a long‐term retrospective data set

Raczyński,

Dyer

2023

Hydrological Processes

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Utilizing simulated daily flow values for 61 948 stream nodes from the National Water Model (NWM) v.2.1 retrospective data set, which covers the period 1979–2020, streamflow peaks (SFP) were determined using an objective threshold method based on the Fisher‐Jenks breakpoint algorithm. This approach provides estimates of low probability, high in‐channel water level conditions. Strong spatial relations in temporal streamflow peak distribution were observed, with four main spatial clusters covering: (1) the central parts of Mississippi to South Carolina; (2) the south and north parts of Mississippi to South Carolina; (3) Florida, the Gulf Coast, and parts of North Carolina and Virginia; and (4) the Atlantic Coast and parts of the Gulf Coast. The first area is characterized by high multiannual SFP occurrence with long total durations, high contribution to total discharge, and occurrence throughout the year with peaks in February and March. Increasing annual peak trends are present locally. The second area is characterized by similar parameters with increased flash flooding potential. In the third area, lower occurrence and share in total discharge are observed, with two peaks of occurrence in the September–October and March periods. In the fourth region, the lowest occurrences and shortest durations are present, along with strong seasonality manifested in September–October occurrences that constitute over 80% of all SFP volumes. Decreasing trends in maximal monthly flows for the June–October period are also observed here. The results provide valuable regionalized information about historical high flow characteristics across the southeast United States, which can be used as a basis for improved long‐term flood prediction based on seasonality models and constitute a baseline for defining regional changes in high flow frequency and distribution.

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Section: Trendscontrasting

confidence: 59%

Quantifying patterns of streamflow peaks over the southeastern United States using a long‐term retrospective data set

Raczyński,

Dyer

2023

Hydrological Processes

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“…The maximal number of episodes increased from 200 for Q 10 to 300 for Q obj , which translates to an average of 8.4 days per episode for Q obj and 6.3 days per episode for Q 10 per year. The low flows identified by the objective method are longer, which allows for the inclusion of periods occurring in streamflow, even when additional criteria, of a minimal time of 7 days, are applied [12,38].…”

Section: Resultsmentioning

confidence: 99%

“…This sometimes leads to a large discretization of the flow values, i.e., the lowest flows can have repeated values in a dataset. If the data uniqueness is greater than 90%, then the use of the Q 10 as the threshold will represent statistical information; however, in some cases, for example with the National Water Model (NWM) retrospective data, minimum streamflow values are often repeated for extended periods [38]. In this case, the FDC flattens out on the lower flows, with the 10th percentile being equivalent to higher percentile values (i.e., 15th or 20th percentile).…”

Section: Introductionmentioning

confidence: 99%

Development of an Objective Low Flow Identification Method Using Breakpoint Analysis

Raczyński

Dyer

2022

Water

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Low flow events (a.k.a. streamflow drought) are described as episodes where stream flows are lower or equal to a specified minimum threshold level. This threshold is usually predefined at the methodological stage of a study and is generally applied as a chosen flow percentile, determined from a flow duration curve (FDC). Unfortunately, many available methods for choosing both the percentile and FDCs result in a large range of potential thresholds, which reduces the ability to statistically compare the results from the different methods while also losing the natural character of the phenomenon. The aim of this work is to introduce a new approach for low flow threshold calculation through the application of an objective approach using breakpoint analysis. This method allows for the identification of an environmental moment of river transition, from atmospheric feed flows to base flow, which characterizes the moment at the beginning of the hydrological drought. The method allows for not only the capture of the genesis of a low flow event but, above all, unifies the approach toward threshold levels and completely excludes the impact of the subjective researcher’s decisions, which occur at the methodological stage when selecting the threshold criteria or when choosing a respective percentile. In addition, the method can be successfully used in datasets characterized by a high level of discretization, such as numerical model data, where the subsurface runoff component is not described in sufficient detail. Results of this work show that the objective identification method is better able to capture the occurrence of a low flow event, improving the ability to identify hydrologic drought conditions. The proposed method is published together with the Python module objective_thresholds for broad use in other studies.

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“…On these, the US EPA 7Q10 approach was used to calculate the annual‐minimum 7‐day average flow discharge that occurs with a 10‐year recurrence interval (i.e. 7Q10) (Dyer et al, 2022). 7Q10 has been used in Australia, Europe and the United States (Petheram et al, 2008; Stanton et al, 2007).…”

Section: Regional Setting and Methodsmentioning

confidence: 99%

Detection of decadal time‐series changes in flow hydrology in eastern Australia: Considerations for river recovery and flood management

Arash,

Fryirs,

Ralph

2023

Earth Surf Processes Landf

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Since European colonisation, many coastal rivers of New South Wales (NSW) have been highly modified by channelisation, flow regulation, sediment mining, intensive grazing and agriculture, deforestation, and riparian vegetation and wood removal. Since the late 1980s, nearly 55% of these rivers have undergone a significant ‘re‐greening’ and geomorphic recovery with changes to instream and riparian roughness. However, little research has been undertaken to quantify if there have been any coeval changes in flow hydrology. Approximately 7000 flow hydrographs with one‐hour time‐steps from 117 gauges on 45 study rivers (17 of 20 coastal catchments of NSW) were used to assess changes to in‐channel and overbank hydrology over decadal timeframes. Hydrograph shape and attenuation characteristics for three morphologically defined flow stages were analysed: in‐channel fresh, high flow and overbank flood. Time‐series analysis was used to quantify changes in flow hydrology from the early‐20th century to present and identify trends occurring between known degradation phases (1910s–1940s and 1940s–1980s) and a recovery phase (1990s to present) for these rivers. Our findings indicate that, on average, and for some key examples, changes in flow hydrology are occurring. Flows are slowing and attenuating as indicated by decreases in flood wave celerity and hydrograph kurtosis, skewness and rate of rise and increases in peak‐to‐peak travel time, flood peak attenuation and flood wave attenuation index. The most significant changes have occurred since the 1980s with the most noticeable effects on the behaviour of high flows (around the bankfull stage). However, there is not a consistent direction change in these indicators in all places. We use these findings to categorise the flow mitigation signal of the study regions and catchments and discuss the implication for river and flood management.

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Identifying Spatial Patterns of Hydrologic Drought over the Southeast US Using Retrospective National Water Model Simulations

Cited by 10 publications

References 28 publications

Quantifying patterns of streamflow peaks over the southeastern United States using a long‐term retrospective data set

Quantifying patterns of streamflow peaks over the southeastern United States using a long‐term retrospective data set

Development of an Objective Low Flow Identification Method Using Breakpoint Analysis

Detection of decadal time‐series changes in flow hydrology in eastern Australia: Considerations for river recovery and flood management

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