Effects of the Time Period Length on the Determination of Long-Term Mean Annual Discharge

Poórová, Jana; Jeneiová, Katarína; Blaškovičová, Lotta; Danáčová, Zuzana; Kotríková, Katarína; Melová, Katarína; Paľušová, Zuzana

doi:10.3390/hydrology10040088

Cited by 4 publications

(5 citation statements)

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“…The results in Poórová et al (2023) indicated as well, that the use of the 30-year long period 1991-2020 is probably suitable, especially for mutual comparison between climatic and hydrological characteristics for climate change research. The period 1991-2020 is the one recommended by WMO as the reference period for current assessment of hydrological situation, to be comparable with climatic assessment based on the same reference period.…”

Section: Discussionmentioning

confidence: 83%

“…In the water management of Slovakia, the reference period 1961-2000 is currently valid in decision-making and hydrological regime evaluation (Šipikalová, 2005). However, various changes of hydrological regime were described in recent studies (Pekárová et al, 2017;Fendeková et al, 2018;Ďurigová and Hlavčová, 2020;Halmová et al, 2022;Poórová et al, 2023). Establishment of a new reference period is a sensitive topic, as the hydrological design values based on this reference period, are a vital part of many decisionmaking processes (e.g., flood protection, hydrological drought management, water use permits, etc.).…”

Section: Introductionmentioning

confidence: 99%

“…This study covers only one part of the evaluation, focused on long-term values analyses. More detailed analyses (the assessment of the data series of monthly discharges, yearly discharge analyses are partially published inPoórová et al, 2023, daily and extreme discharges, long term trends, precipitation, etc.) are needed to fully support the selection of the new reference period (or more of them for specific purposes) used for the water management and decision making needs.…”

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confidence: 99%

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Challenges in selecting the new reference period for long-term hydrological characteristics in Slovakia

Blaškovičová,

Jeneiová,

Kotríková

et al. 2023

AHS

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Establishment of a new reference period is an ongoing topic in Slovakia as the currently used reference period is 1961-2000. This contribution focuses on the assessment of spatial and temporal changes in the mean long-term yearly discharges and long-term mean monthly discharges at 140 water-gauging stations. The years 2021 and 2022 have been further evaluated at selected 13 water-gauging stations to assess the possible impacts of using different reference periods (1991-2020, 1981-2020, 1971-2020 and 1961-2000) on the water management. The analyses have confirmed that there are significant changes between long-term values, especially for the period 1991-2020 compared with the reference period 1961-2000, with the highest negative changes in monthly discharges being in April and highest positive changes being in January. Evaluation of mean monthly and annual discharges in 2021 and 2022 for 13 selected water-gauging stations, according to the four above mentioned reference periods, has identified changes especially in set categories of monthly discharges. The same average monthly but also annual flows in one station have fallen into different assessment categories, in several cases. For annual flows the changes have manifested in 6 water-gauging stations in the year 2021 and 2 stations in the year 2022. The number of stations with changes in categories between different reference periods used for particular months have varied from 2 to 8 water-gauging stations in 2021 (62 cases for the whole year) and from 2 to 6 watergauging stations in 2022 (40 cases for the whole year). The highest number of changes for both years were detected in June ( 14) and August and December (11). The selection of the reference period can therefore lead into different set of applied water management rules.

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Section: Discussionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Challenges in selecting the new reference period for long-term hydrological characteristics in Slovakia

Blaškovičová,

Jeneiová,

Kotríková

et al. 2023

AHS

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“…Several State Departments of Transportation (DOTs) in the U.S. have used the risk assessment tool HyRisk, incorporating available data of different lengths and periods in relation to hydrology, hydraulics, and structure [45]. In the current study, since the hydrological regimes are least affected by human activities, the adopted approach is also similar to the approach of using 'normal', 'quasi-periodicities', or 'potential' cycles for hydrologic analysis [46]. Quasi-periodicities or potential cycles imply specific periods for which the watersheds are least disturbed [46]; therefore, such periods can be different across watersheds.…”

Section: Selection Of Sitesmentioning

confidence: 99%

“…In the current study, since the hydrological regimes are least affected by human activities, the adopted approach is also similar to the approach of using 'normal', 'quasi-periodicities', or 'potential' cycles for hydrologic analysis [46]. Quasi-periodicities or potential cycles imply specific periods for which the watersheds are least disturbed [46]; therefore, such periods can be different across watersheds.…”

Section: Selection Of Sitesmentioning

confidence: 99%

Understanding the Challenges of Hydrological Analysis at Bridge Collapse Sites

Ashraf,

Islam

2023

Water

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There is a crucial need for modeling hydrological extremes in order to optimize hydraulic system safety. It is often perceived that the best-fitted distribution accurately captures the intricacies of the hydrological extremes, particularly for the least disturbed watersheds. Thirty collapse sites with the least disturbed watersheds within the Appalachian Highland region in the U.S. are identified and used to test this perception. Goodness-of-fit tests, time series analysis, and comparison of predictor variables are carried out to find out the best-fitted distribution, identify trends and seasonal variation, and assess site variability. The study results are found to be inconclusive and sometimes contradictory; sometimes even complex distribution models do not provide better results. For most sites, the historic peak flow data are best-fitted with multiple distributions, including heavy and light tails. For monthly flow data, seasonal variation and trend cannot be categorized since no definitive, distinct tendency can be identified. When comparing sites best-fitted with a single distribution to sites best-fitted with multiple distributions, significant differences in certain geospatial characteristics are identified. However, these characteristics at the watershed scale are claimed to be less important in predicting the behavior of a flood event. All of these results capture the difficulties and inconsistencies in interpreting the results of hydrologic analysis, potentially reducing the robustness of the hydrologic tools used in the design and risk assessment of bridges.

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Reliability and resilience of environmental flows under uncertainty: reconsidering water year types and inconsistent flow requirements in California

Facincani Dourado,

Viers

2024

Environ. Res. Lett.

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Environmental water allocation in California is a complex legal process involving various government agencies and stakeholders. E-flow requirements can be based on annual runoff typologies called water year types (WYTs), which dictate water volume, timing, and duration. In this study, we examined hydropower licensing documents of the major water and power projects in the Central Sierra Nevada to catalog e-flow requirements by WYT. In this study case, we identify how e-flow mitigation and allocation strategies vary across and within different basins. Additionally, we assessed the impacts of climate change on hydrology, the frequency of WYTs identified, and the reliability and resilience of e-flows using future projections (2031-2060) of 10 Global Circulation Models (GCMs). We then propose a potential adaptation strategy using a 30-year moving percentiles approach to recalculate WYTs. We identified that in most cases WYTs are not adopted, as e-flows generally include little to no variation across years, and limited seasonal fluctuations. Eight WYT classifications systems were identified, and their WYT distributions statistically significantly changes across all GCMs, even though most GCMs indicate no statistically significant change in hydrology. Disparities in future impacts are observed among and within hydropower projects, with some river reaches showing negative impacts on reliability and resilience. The adaptation strategy can generally boost resilience and improve reliability, but simply updating existing WYT thresholds without flexible regulatory frameworks reconsidering WYTs and e-flows thresholds, may not yield substantial improvements. Challenges in managing e-flows in California within regulatory and hydroclimatic contexts are intricate due to the lack of standardized approaches, leading to inconsistencies and potential conflicts among stakeholders, that will likely be exacerbated by climate change. Thus, we emphasize that targeted, site-specific, and adaptive management strategies are crucial, besides the need for a harmonized and consistent approach to defining and applying WYT categories and methods and/or e-flow assessments.

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Effects of the Time Period Length on the Determination of Long-Term Mean Annual Discharge

Cited by 4 publications

References 9 publications

Challenges in selecting the new reference period for long-term hydrological characteristics in Slovakia

Challenges in selecting the new reference period for long-term hydrological characteristics in Slovakia

Understanding the Challenges of Hydrological Analysis at Bridge Collapse Sites

Reliability and resilience of environmental flows under uncertainty: reconsidering water year types and inconsistent flow requirements in California

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