Wyniki wyszukiwania - Biblioteka Nauki

1

Initial Results of Nonhierarchical Cluster Methods Use for Low Flow Grouping

100%

Cupak A.

Journal of Ecological Engineering

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2017

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tom Vol. 18, nr 2

44--50

EN

In the paper the possibility of using statistical method for data agglomeration, i.e. nonhierarchical cluster analysis for low flow grouping was made. The study material included daily flows from the multi-year period of 1963–1983 collected for 19 catchments, located in the upper Vistula basin. Regions with the same flow were determined with the use of nonhierarchical cluster analysis (K-means). Groups were characterized by low flow and selected physiographic and meteorological features of the catchments. The procedure of catchments assigning to the clusters was started from two clusters and finished at five. The next moving and assigning of catchments into clusters resulted in a cluster in which there was only one catchment (for five clusters). Another objects’ delineation did not give an objective effects, based on which it was difficult to determine a clear criterion of assigning each catchments into the clusters. The last step involved development of the models reflecting correlation and regression relationships. The identified clusters comprised catchments similar in terms of unit runoff, watercourse length, mean precipitation, median altitude, mean catchment slope, watercourse staff gauge zero, area covered by coniferous forests, arable lands, and soils.

2

Classification of low flow and hydrological drought for a river basin

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Tokarczyk T.

Acta Geophysica

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2013

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tom Vol. 61, no. 2

404--421

EN

The occurrence of drought is one of the characteristic features of Polish climate. Drought usually lasts for many weeks and covers consid- erable area causing economic and social losses. Due to the influence which drought has on environment, economy and society, more and more research and implementation works are devoted to issues concerning its occurrence, risk assessment, monitoring, and forecasting. Literature indicates that hydrological droughts are most often associated with low flow periods on rivers. The paper presents analyses of hydrological drought periods on the basis of hydrological drought index (HDI) for selected Nysa Kłodzka study basin (SW part of Poland). Analyses were carried out in relation to the Maximum Credible Hydrological Drought (MCHD). In addition, attempts were taken to assess the hydrological drought based on atmospheric drought focused on application in ungauged basins in terms of hydrological monitoring.

3

Spatial variability of low-flows in the upper Warta River catchment

100%

Kozek M.

Acta Scientiarum Polonorum. Formatio Circumiectus

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2018

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tom 17

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nr 3

EN

Low-flows are an important component of the river regime. Their identification advances our knowledge about the formation of water resources in drought conditions. The analyses that we have carried out aimed to indicate the spatial structure of these flows. Our study area was the Warta River catchment up to the water-gauge at Sieradz. The input research material consisted of a sequence of daily discharge data for 12 gauging stations located in this catchment, in the period of 1971-2000, made available by IMGW-PIB. At the first stage, periodic flows based on flow time-duration curve and annual minimum flows were determined. Their values have been converted into specific flows, which facilitated the conduct of comparative analyses. On the basis of the obtained results, the spatial variability of low-flows in studied catchment was evaluated. The annual number of days with low-flows was identified for all gauge sections. The dynamics and distribution of low flow appearing in the multiannual period were evaluated. The analyses we have carried out made it possible to identify the factors, which determine the structure of low-flows. Research results have been illustrated with relevant maps and graphs.

PL

Przepływy niżówkowe stanowią ważny element reżimu rzecznego. Ich rozpoznanie poszerza wiedzę o kształtowaniu się zasobów wodnych w warunkach suszy. Przeprowadzone analizy miały na celu ocenę przestrzennej struktury tych przepływów. Obszarem badań była zlewnia Warty po wodowskaz w Sieradzu. Wejściowy materiał badawczy stanowiły serie przepływów dobowych z okresu 1971–2000 dla 12 wodowskazów zlokalizowanych w tej zlewni, udostępnione przez IMGW-PIB. W pierwszym etapie wyznaczono przepływy okresowe na bazie krzywej czasów trwania wraz z wyższymi oraz roczne przepływy minimalne. Ich wartości zostały przeliczone na odpływy jednostkowe, dzięki czemu możliwe były analizy porównawcze. Na podstawie uzyskanych wyników dokonano oceny przestrzennej zmienności przepływów niżówkowych w badanej zlewni. Dla wszystkich przekrojów zidentyfikowano roczną liczbę dni z przepływem niżówkowym. Ocenie poddano także dynamikę i rozkłady minimów przepływu, pojawiających się w okresie wieloletnim. Przeprowadzone analizy pozwoliły na wyodrębnienie czynników decydujących o strukturze przepływów niżówkowych. Wyniki badań zostały zilustrowane na stosownych mapach i wykresach.

4

Regionalisation of watersheds with respect to low flow

88%

Cupak A. , Michalec B.

Journal of Water and Land Development

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2022

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tom no. 55

47--55

EN

The aim of the study was to compare two grouping methods for regionalisation of watersheds, which are similar in respect of low flow and chosen catchments parameters (physiographic and meteorological). In the study, a residual pattern approach and cluster analysis, i.e. Ward’s method, were used. The analysis was conducted for specific low flow discharge q95 (dm3∙s-1∙km-2). In the analysis, 50 catchments, located in the area of the upper and central Vistula River basin, were taken. Daily flows used in the study were monitored from 1976 to 2016. Based on the residual pattern approach (RPA) method, the analysed catchments were classified into two groups, while using the cluster analysis method (Ward’s method) - into five. The predictive performance of the complete regional regression model checked by cross-validation R2cv was 47% and RMSEcv= 0.69 dm3∙s-1∙km-2. The cross validation procedure for the cluster analysis gives a predictive performance equal to 33% and RMSEcv= 0.81 dm3∙s-1∙km-2. Comparing both methods, based on the cross-validated coefficient of determination (R2cv), it was found that the residual pattern approach had a better fit between predicted and observed values. The analysis also showed, that in case of both methods, an overestimation of specific low flow discharge q95 was observed. For the cross-validation method and the RPA method, the PBIAS was -10%. A slightly higher value was obtained for the cross-validation method and models obtained using cluster analysis for which the PBIAS was -13.8%.

5

Hydrological responses to large-scale changes in land cover of river watershed: Review

88%

Muhammed H. H. , Mustafa A. M. , Kolerski T.

Journal of Water and Land Development

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2021

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tom no. 50

108--121

EN

Despite many studies on the hydrological responses to forest cover changes in micro and mesoscale watersheds, the hydrological responses to forest cover alterations and associated mechanisms through the large spatial scale of the river watershed have not been comprehensively perceived. This paper thus reviews a wide range of available scientific evidence concerning the impacts exerted by the forest removal on precipitation, water yield, stream flow, and flow regimes. It is concluded that there is no statistical correlation between forest cover and precipitation and water yield at the micro and mesoscale. In contrast, there is a relative correlation coefficient (r = 0.77, p < 0.05) between forest cover and water yield at large scales (>1000 km2). These findings help our understanding of the hydrological response to forest disturbance at large and regional scale and provide a scientific perception to future watershed management in the context of human activities and natural hazards.

6

Regionalization of catchments with use hierarchical cluster analysis methods

88%

Cupak A.

Teka Komisji Ochrony i Kształtowania Środowiska Przyrodniczego

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2013

|

tom 10

7

Projection of low flow conditions in Germany under climate change by combining three RCMs and a regional hydrological model

88%

Huang S. , Krysanova V. , Hattermann F. F.

Acta Geophysica

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2013

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tom Vol. 61, no. 1

151--193

EN

The present study is aimed to: (a) project future low flow conditions in the five largest river basins in Germany, and (b) to account for the projections uncertainties. The eco-hydrological model SWIM was driven by different regional climate models (REMO, CCLM, and Wettreg) to simulate daily river discharg es in each study basin. The 50-year low flow was estimated for the period 1961 to 2000, and its return period was assessed for two scenario periods, 2021-2060 and 2061-2100, using the generalized extreme value distribu tion. The 50-year low flow is likely to occur more frequently in western, southern, and parts of central Ger- many after 2061, as suggested by more than or equal to 80 per cent of the model runs. The current low flow period (from August to September) may be extended until late autumn at the end of this century. The return period of 50-year deficit volume shows a similar temporal and spatial pattern of change as for the low flow, indicating slightly less severe con- ditions with lower confidence. When compared with flood projections for the same area using the same models, the severer low flows projected in this study appear more pronounced, consistent, and have lower uncertainty.

8

Low-flow discharge deficits assessment, applying constant and variable low-flow threshold levels, as illustrated with the example of selected catchments in the Vistula River basin

88%

Tomaszewski E.

Acta Scientiarum Polonorum. Formatio Circumiectus

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2018

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tom 17

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nr 3

EN

In the present study, we have assessed low-flow discharge deficits, and the characteristics of the low flows at a constant and variable (monthly) low-flow threshold. The low-flow truncation level was identified based on the 70th percentile from the flow duration curve (Q70%). Q95% was assumed to be the threshold for the deep low-flow discharge. Thirteen catchments in the Vistula basin, varying in size, river regime, and physico-geographical conditions, were selected for the study. The input data was a series of daily discharge data sets from the period 1951–2016, made available by IMGW-PIB (Polish Institute of Meteorology and Water Management – National Research Institute). Analyses were conducted of drought flow discharge deficit volume in absolute and relative values, and low-flow duration and deficits contributing to severe low-flows were calculated for temporal scales of months and years. Comparison of the obtained results led us to the determination of the basic factors affecting the formation of low-flow deficits, and the indication of restrictions when applying fixed and variable criteria for identifying river low-flows.

PL

W opracowaniu dokonano oceny niedoborów odpływu niżówkowego i charakterystyk przepływów niżówkowych przy stałym i zmiennym (miesięcznie) przepływie granicznym niżówki. Niżówki całkowite identyfikowano w oparciu o 70. percentyl z krzywej czasów trwania przepływu wraz z wyższymi (Q70%). Za przepływ graniczny niżówki głębokiej przyjęto Q95%. Do badań wytypowano 13 zlewni leżących w dorzeczu Wisły, charakteryzujących się różną wielkością, reżimem rzecznym i warunkami fizycznogeograficznymi. Danymi wejściowymi były serie dobowych przepływów z okresu 1951–2016, udostępnione przez IMGW-PIB. Analizie poddano objętość niedoboru odpływu niżówkowego wyrażonego wartościami względnymi i bezwzględnymi, czas trwania przepływów niżówkowych oraz udział niedoborów odpływu pojawiających się podczas niżówek głębokich. Badania prowadzono w układzie rocznym i miesięcznym. Porównanie uzyskanych wyników doprowadziło do określenia podstawowych czynników wpływających na formowanie niedoborów odpływu niżówkowego oraz wskazania ograniczeń przy stosowaniu stałych i zmiennych kryteriów identyfikacji niżówki rzecznej.

9

The Vistula River low flows in Warsaw in the 21st century

75%

Kaznowska E. , Hejduk A. , Kempinski C.

Acta Scientiarum Polonorum. Formatio Circumiectus

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2018

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tom 17

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nr 1

EN

The aim of the paper is an analysis of low flows – a phenomenon of persistent low water levels and flows in the riverbed – of the Vistula River at the Warszawa-Nadwilanówka gauging station. The study concerned the beginning of the 21st century, against the 1951–2000 period. In order to determine the low flows on the daily flows hydrographs, they were cut-off by the threshold level method. According to the adopted criterion, low flows are rather rare on the Vistula in Warsaw. The longest and most severe drought in terms of outflow deficit occurred in 1951. In the last years of the studied period (2003, 2012, 2015), droughts have reached a considerable sizes, but were no greater than the low flow observed in 1951. Since 1985 no winter low flows have been recorded.

PL

Celem pracy jest ocena zjawiska niżówki, będącej okresem utrzymywania się niskich stanów wody i przepływów w korycie rzeki. Analiza ich występowania w profilu Warszawa-Nadwilanówka na Wiśle, dotyczy początku XXI wieku, została wykonana w odniesieniu do wielolecia 1951–2000. W celu wyznaczenia niżówek na hydrogramach dobowych przepływów odcięto je za pomocą przepływu granicznego. Według przyjętego kryterium niżówki na Wiśle w Warszawie występują rzadko. Najdłuższa i najsurowsza pod względem deficytu odpływu była niżówka w 1951 roku. W ostatnich latach badanego wielolecia (2003, 2012, 2015) niżówki osiągnęły znaczne rozmiary, lecz nie były większe od dotychczas zaobserwowanej niżówki z 1951 roku. Od roku 1985 nie zanotowano niżówek zimowych.

10

Hydrological responses to large-scale changes in land cover of river watershed: Review

75%

Muhammed H. H. , Mustafa A. M. , Kolerski T. , Muhammed H. H. , Mustafa A. M. , Kolerski T.

|

11

Stability of high and low flow periods on European rivers

75%

Wrzesinski D.

Badania Fizjograficzne nad Polską Zachodnią. Seria A: Geografia Fizyczna

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2015

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tom 66

12

On the instabilities of estimated distributions of the POT (Peak Over Threshold) low flow characteristics

75%

Jakubowski W.

Meteorology Hydrology and Water Management. Research and Operational Applications

|

2015

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tom 03

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nr 2

EN

In a certain stream gauge profile, consider the low flow flows determined with the POT (Peak Over Threshold) method. Each of the flows can be described by three characteristics – deficit, duration and minimal flow. Values of the three-dimensional random variable depend on the choice of truncation level Qg (threshold flow) – POT method parameter. It is typically assumed that the threshold level is included within the range from Q95% to Q60% (Tallaksen, van Lanen 2004). However, in computational practice the Qg value is determined at the level of either Q90% to Q70%. This choice is made mainly from the hydrological (not statistical) point of view. In this paper the influence of the threshold flow on the form of estimated distributions of each of the above three characteristics is considered. The following distributions are chosen: − GEV (generalised extreme value distribution) – while examining the distribution of extremes; − log-normal – in the non-extreme case. In each of the examined stream gauge profiles the following algorithm was used: 1. from the curve of duration sums, two flow values Q90% and Q55% are chosen 2. for each flow from the range (Q90%, Q55%), using the Zelenhasić method (1987), a three-dimensional sequence is determined of observed deficits, durations and minimal flow values; 3. for each of the one-dimensional sequences, the parameters of the above distributions are estimated. The variability of the estimated quantiles and their intervals of confidence were shown with the example of three gauge profiles – Kuripapango (New Zealand), Bogusław (Prosna) and Bystrzyca Kłodzka (Nysa Kłodzka).

13

Cluster analysis in determination of hydrologically homogeneous regions with low flow

75%

Cupak A. , Walega A. , Michalec B.

Acta Scientiarum Polonorum. Formatio Circumiectus

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2017

|

tom 16

|

nr 1

14

Rozkłady prawdopodobieństwa niżówek maksymalnych

75%

Jakubowski W.

Przegląd Geofizyczny

|

2005

|

tom Z. 3-4

229-248

EN

The complete method, based on Zelenbasic and Salvai model, for estimating unknown distributions of low flow indices (drought amount and duration) is presented. Good fiting is shown on data taken from two different catchments: upper Nysa Kłodzka and Odra rivers.

15

Określenie przepływów niskich w zlewniach niekontrolowanych z wykorzystaniem regionalizacji

63%

Cupak A.

Gaz, Woda i Technika Sanitarna

|

2012

|

tom Nr 2

62-64

PL

Określenie modeli zależności regresyjnych dla przepływu niskiego o czasie trwania wynoszącym 95% czasu w całym okresie badawczym. Zależności regresyjne i korelacyjne określono dla regionów homogenicznych wyznaczonych na podstawie statystycznej metody grupowania - analizy skupień.

EN

Determination of dependency regression models for low flow with a duration of 95% of the time throughout the study period. Regression and correlation dependencies defined for the homogeneous regions identified on the basis of statistical methods- cluster analysis grouping.

16

Exceedance probability of selected low characteristic flows in mountain catchments

63%

Weglarczyk S.

Infrastruktura i Ekologia Terenów Wiejskich

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2014

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nr IV/3

EN

In Polish hydrology and water management the term characteristic flow exists denoting a specific value of flow at the given cross-section of a river calculated as the long-term minimum, mean, median or maximum calculated using the annual minimum, mean, median or maximum flow taken for each year from a series of (usually) daily flows. Some of these characteristic flows are used to define the low-flow (o drought) periods while the another criterion: a percentage flow Qp taken from the long-term flow duration curve is also widely used. In the paper the study on the frequency structure the empirical exceedance probability of a given characteristic flow made for some low and average characteristic flows (SNQ, WNQ, NSQ and SSQ) is presented. The results show that the exceedance probability of a given characteristic flow is variable, and the amount of this variability may be large, as is the case of WNQ and NSQ. So assigning a characteristic flow to a single FDC quantile value Qp (as can be find in the literature) cannot be justified. Correlation analysis made for the pairs (P. , characteristic flow), ( P., catchment area) and (P. , gauging station elevation) revealed some significant correlations. Only for SNQ is not correlated at all; correlation for other characteristic flows is statistically significant for at least one of the cases. The highest correlations (greater than 0.4 in absolute values) were found for the pairs ( P, gauging station elevation) for NSQ and, for SSQ, ( P, SSQ) and ( P, catchment area).

17

Zasoby wodne województwa dolnośląskiego w okresach suszy

63%

Tokarczyk T. , Adynkiewicz-Piragas M. , Bogusz A. , Otop I. , Urban G.

Zeszyty Naukowe. Inżynieria Środowiska / Uniwersytet Zielonogórski

|

2007

|

tom nr 133 (13)

411-419

PL

Województwo dolnośląskie jest jednym z najuboższych w wodę obszarów kraju. Pierwszoplanową rolę w kształtowaniu stosunków hydrologicznych odgrywają tutaj opady atmosferyczne oraz ich rozkład w czasie i na obszarze dorzecza Odry. Naturalną przyczyną niżówek jest deficyt zasilania rzeki, który może być spowodowany brakiem opadów, dużym parowaniem oraz długotrwałymi mrozami. Brak opadów powoduje, że rzeki zasilane są jedynie przez wody podziemne. Na wielkość zasilania ma wpływ długość okresu bezopadowego. Im on jest dłuższy, tym bardziej wyczerpują się zasoby wód podziemnych i zasilanie rzek maleje. W okresie letnim, gdy wysokie temperatury powietrza ułatwiają szybkie parowanie wody oraz występują niewielkie opady, zasilanie rzek maleje. Współdziałanie tych czynników może doprowadzać do powstawania niżówek letnich. Zasoby wodne w takich okresach ulegają stopniowemu sczerpywaniu, co doprowadzić może do wystąpienia deficytów w zaspokajaniu potrzeb wszystkich użytkowników. W artykule oceniono zasoby wodne na podstawie wybranych okresów niżówkowych w rzekach obszaru województwa dolnośląskiego, określono ich objętość deficytu oraz czas trwania.

EN

The Dolnoslaskie Province is the one of the poorest region in water supply in the whole territory of Poland. The crucial role for hydrological conditions plays precipitations and also their temporal and spatial distribution in Odra basin. The natural reason of low flow in rivers is river supply scarcity which is caused by precipitations lack and increasing of evaporation. The lack precipitation caused that rivers are supply by only groundwater. In summer season when high temperatures help to evaporation increasing water supply are decreased. Water resources in such periods are gradually bailing. It can lead to appearance breaks in water demand for all users. In this paper water resources were assessed on the basis of low flow periods in rivers Dolnoslaskie Province territory and described their deficit volume and duration.

18

A comparison of hydrological drought characteristics defined by the POT and SPA methods in the Dunajec River basin

63%

Baran-Gurgul K.

Infrastruktura i Ekologia Terenów Wiejskich

|

2014

|

nr IV/3

EN

This paper addresses the problem of how drought definition by POT and SPA methods influences drought characteristics. Using the 1984- 2013 daily flows at 24 selected gauging stations in the Dunajec river basin and assuming two threshold levels Q70% and Q95% and four minimum drought durations (5, 7, 10 and 14 days) as the pre-set criteria, it was shown that, when compared to the POT method, the application of the SPA method usually leads to less number of droughts and, consequently, of longer duration. The SPA method, differently from POT, reduces dramatically the number of inter-event times, which suggests that some adjacent POT droughts may be dependent and should be pooled.

19

The spatial distribution of low flows in Poland not exceeded at an assumed probability

63%

Bartnik A.

Geographia Polonica

|

2010

|

tom 83

|

nr 1

20

Data Based Mechanistic rainfall-flow models for climate change simulations

63%

Romanowicz R. J.

Annals of Warsaw Agricultural University - SGGW. Land Reclamation

|

2006

|

nr 37

3-13