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1

Impact of Land Use/Cover Changes on the Flow of the Zarqa River in Jordan

Shammout Maisa'a W., Shatanawi Khaldoun, Al-Bakri Jawad, Abualhaija Mahmoud M.

Journal of Ecological Engineering

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2021

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Vol. 22, nr 10

40--50

EN

This paper investigated the impact of land use/cover changes on the flow of the Zarqa River in Jordan over a period of twenty-eight years. The land use/cover maps were derived using a set of medium spatial images with full scenes for the years 1989, 2002, 2011 and 2017. These images correspond to the river flow data for the same hydrological rainy seasons. The component of the river flow consists of the base-flow, flood and contribution of effluent from treatment plants. Base-flow was separated from hydrographs and effluent contribution was obtained. Runoff coefficient was determined as the ratio of flood volume to rainfall volume. The land use/cover maps were classified as urban fabrics, bare rocks, open rangelands and bare soils, agricultural areas, agro-forestry, and water bodies. During the study period, urban areas increased from 4.87% to 16.14%, and agricultural areas increased from 21.69% to 31.66%. The areas of rangelands and bare soil decreased from 34.91% to 22.57% and bare rocks from 35.98% to 27.57%, respectively. The increase in urban and agricultural areas resulted in runoff coefficient improvement from 1.89% in 1989/1990 to 2.72% for 2016/2017. The results could be useful for planners and decision makers for future flow management in the Zarqa River Basin. The approach and results of this study confirm the findings of similar studies for land and water management.

2

Hydrauliczne skutki pogłębienia toru wodnego Świnoujście-Szczecin

Kurnatowski Jacek

Gospodarka Wodna

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2021

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Nr 11

15--18

PL

W artykule przedstawiono wyniki matematycznego modelowania rozkładu przepływów w sieci rzek i kanałów dolnej Odry po pogłębieniu toru wodnego Świnoujście-Szczecin do głębokości 12,5 m. Przeprowadzona analiza wykazuje prognozowane zmiany przepływów na poszczególnych odcinkach sieci do ok. 20% wartości sprzed pogłębiania. Budzi to obawy destabilizacji ruchu rumowiska w sieci, zwłaszcza możliwości nadmiernego zamulania niektórych odcinków.

EN

The paper presents the results of mathematical modeling of the flows distribution in the network of rivers and canals of the lower Oder after deepening the Świnoujście-Szczecin fairway to a depth of 12.5 m. The conducted analysis shows the anticipated changes of flows at individual network sections up to approx. 20% of the pre-dredging values. This raises concerns about the destabilization of sediment motion in the network, especially the possibility of excessive silting of some sections.

3

Anthropogenic and Climatic Causality of Changes in the Hydrological Regime of the Dnieper River

Pichura Vitalii Ivanovich, Potravka Larisa Aleksandrovna, Skrypchuk Petro Mikhalovich, Stratichuk Natalia Vladimirovna

Journal of Ecological Engineering

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2020

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Vol. 21, nr 4

1--10

EN

The intensive use of water resources and the transformation of natural landscapes under the influence of human economic activity have led to changes in the natural water balance of river drainage basins. The negative processes thereof are intensified by climatic changes that have significantly disturbed the hydrological regime, determined by changes in water content and river flow dynamics. The retrospective study and prediction of the flow of the Dnieper River was carried out using multivariate statistics and adaptive methods of nonlinear time series analysis. The anomalous features were identified and the main periods of changes in the water regime of the river for 190 years (1818–2008) were determined using the standard root-mean-square deviation and wavelet analysis. As a result of non-linear prediction, it was determined that if the tendency of anthropogenic and climatic formation of the water regime of the Dnieper River sustains, there is a 90% probability of insignificant but steady trend and cyclical reduction of the average annual flow by 1.6 m3/s per year to 1120 ± 270 m3/s by 2040. The results of the detailed retrospective analysis for 190 years and the prediction of the probability of changes in the flow of the Dnieper river confirm the previous conclusions of many scientists regarding the significant transformation of the ecosystem of the transboundary river and provide new knowledge regarding the main stages of formation of the water regime and the probability of further regulation of the flow of the Dnieper river if the current conditions of the negative impact of economic activities are maintained in the transboundary basin.

4

Water Retention Problem in the Mountain Areas: a Case of Sola River Flows, Polish Carpathians

Jaguś Andrzej

Journal of Ecological Engineering

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2019

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Vol. 20, nr 11

167--177

EN

The paper considers mountain rivers, which usually feature high dynamics of hydrological phenomena. The variability of the Sola river flows in the Polish Carpathians is presented based on water-gauge measurements from the hydrological long-period of 1956-2015. The flows for the upper section of the river, where no storage reservoirs are found, were analysed. A broad range of flows was shown – from 0.59 to 1250 m3/s at a mean flow of 15.5 m3/s. It was also shown that within a year, the flows grow in the spring (thaw freshets) and summer periods (rainwater freshets). Mainly the summer freshets are dangerous, consisting in a sudden rise of the flow due to rains. This is shown by the high values of maximum flows in June and July. In the case of mountain rivers, such as the Sola river, it is necessary to undertake the actions stabilising the flows, which on the one hand have flood-prevention importance, and on the other hand protect the water resources in long dry periods. The actions should be concentrated on the proper arrangement of the catchment area, slowing down the rainwater outflow. Appropriate land use is especially important (distribution of forests, of arable and developed areas) depending on the land elevation above the sea level and inclination, as well as creation of small storage facilities.

5

Short-term dynamics of river water turbidity

Chalov S. R., Tsyplenkov A. S.

Geography and Tourism

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2018

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Vol. 6, No. 1

7--14

EN

An overview of the recently collected datasets of highly discrete water turbidity measurements has allowed for the first hydrological and geographical analysis of short-term fluctuations in water turbidity and the composition of suspended sediments. The novel methodology has been developed to estimate a value of TI, which is the ratio of the difference between the maximum and minimum turbidity for a short period of time (ΔTi) (1 hour with the measurement frequency of 20 minutes) and the total turbidity difference for the water regime phase under study (ΔTHE). Higher TI values correspond to a greater contribution of diurnal (20-minute) turbidity fluctuations to the seasonal variability of sediment yield. Rivers have been grouped according to the value of water turbidity fluctuations within one hour (20-minute): glacier-fed rivers (the Tarfala, the Dzhankuat) (TI amounts to 0.17-0.22); volcanic rivers (0.22–0.25) and lowland rivers (the Selenga, the Western Dvina) (0.09).

6

Trend detection in river flow indices in Poland

Piniewski M., Marcinkowski P, Kundzewicz Z. W.

Acta Geophysica

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2018

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Vol. 66, no. 3

347--360

EN

The issue of trend detection in long time series of river flow records is of vast theoretical interest and considerable practical relevance. Water management is based on the assumption of stationarity; hence, it is crucial to check whether taking this assumption is justified. The objective of this study is to analyse long-term trends in selected river flow indices in small- and medium-sized catchments with relatively unmodified flow regime (semi-natural catchments) in Poland. The examined indices describe annual and seasonal average conditions as well as annual extreme conditions—low and high flows. The special focus is on the spatial analysis of trends, carried out on a comprehensive, representative data set of flow gauges. The present paper is timely, as no spatially comprehensive studies (i.e. covering the entire Poland or its large parts) on trend detection in time series of river flow have been done in the recent 15 years or so. The results suggest that there is a strong random component in the river flow process, the changes are weak and the spatial pattern is complex. Yet, the results of trend detection in different indices of river flow in Poland show that there exists a spatial divide that seems to hold quite generally for various indices (annual, seasonal, as well as low and high flow). Decreases of river flow dominate in the northern part of the country and increases usually in the southern part. Stations in the central part show mostly ‘no trend’ results. However, the spatial gradient is apparent only for the data for the period 1981–2016 rather than for 1956–2016. It seems also that the magnitude of increases of river flow is generally lower than that of decreases.

7

What can we learn from the projections of changes of flow patterns? Results from Polish case studies

Piniewski M., Meresa H. K., Romanowicz R., Osuch M, Szcześniak M., Kardel I., Okruszko T., Mezghani A., Kundzewicz Z. W.

Acta Geophysica

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2017

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Vol. 65, no. 4

809--827

EN

River flow projections for two future time horizons and RCP 8.5 scenario, generated by two projects (CHASE-PL and CHIHE) in the Polish-Norwegian Research Programme, were compared. The projects employed different hydrological models over different spatial domains. The semi-distributed, process-based, SWAT model was used in the CHASE-PL project for the entire Vistula and Odra basins area, whilst the lumped, conceptual, HBV model was used in the CHIHE project for eight Polish catchments, for which the comparison study was made. Climate projections in both studies originated from the common EURO-CORDEX dataset, but they were different, e.g. due to different bias correction approaches. Increases in mean annual and seasonal flows were projected in both studies, yet the magnitudes of changes were largely different, in particular for the lowland catchments in the far future. The HBV-based increases were significantly higher in the latter case than the SWAT-based increases in all seasons except winter. Uncertainty in projections is high and creates a problem for practitioners.

8

Analysis of prognosis of lowland river bed erosion based on geotechnical parameters

Smaga A.

Studia Geotechnica et Mechanica

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2015

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Vol. 37, nr 4

57--63

EN

The river erosion is a complex process, the dynamics of which is very difficult to predict. Its intensity largely depends on hydraulic conditions of the river channel. However, it is also thought that natural resistance of the subsoil has a great influence on the scale of the erosion process. Predicting the effects of this process is extremely important in the case of constructing a piling structure (for example, artificial reservoirs). The partition of the river channel causes significant lowering of the river channel bed downstream the dam which threatens the stability of hydro technical and engineering (bridges) buildings. To stop this unwanted phenomenon, stabilizing thresholds are built. However, random location of thresholds significantly reduces their effectiveness. Therefore, taking under consideration natural geotechnical conditions of the subsoil appears to be extremely important. In the light of the current development of in-situ tests in geotechnics, an attempt to use results from these tests to predict the bed erosion rate was made. The analysis includes results from CPTU and DPL tests, which were carried out in the Warta River valley downstream the Jeziorsko reservoir. In the paper, the general diagrams for the procedure of obtaining and processing the data are shown. As a result, the author presents two multidimensional bed erosion rate models built based on hydraulic data and results from CPTU or DPL tests. These models allow taking more effective actions, leading to the neutralization of the effects of the intensive bed erosion process.

9

Ocena warunków hydromorfologicznych rzek w zlewniach zurbanizowanych metodą River Habitat Survey

Łabaj P., Hamerla A.

Prace Naukowe GIG. Górnictwo i Środowisko / Główny Instytut Górnictwa

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2012

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nr 4

109--121

PL

Do oceny warunków hydromorfologicznych cieków stosuje się szereg metod. Jedną z nich jest metoda oceny wód płynących River Habitat Survey (RHS), stanowiąca narzędzie do szczegółowego opisu warunków hydromorfologicznych rzek na podstawie rejestracji elementów środowiska doliny rzecznej. W celu przetestowania możliwości stosowania metody RHS do oceny warunków hydromorfologicznych rzek miejskich przeprowadzono badania na wybranych odcinkach czterech rzek przepływających przez centralną część konurbacji katowickiej. Uzyskane wyniki wykazują duże zróżnicowanie. Różnice otrzymanych wyników wystąpiły zarówno między badanymi rzekami, jak i w obrębie tego samego cieku na odcinkach ze sobą sąsiadujących. Przyczyn takiego zróżnicowania wyników, poza urozmaiconymi warunkami zlewniowymi śląskich miast, należy upatrywać w niewielkiej liczbie czynników silnie wpływających na ocenę końcową wskaźników naturalności i przekształcenia siedliska. Wskazane jest podjęcie próby zastosowania metody Urban River Survey (URS), która stanowi zmodyfikowaną wersję metody RHS, dostosowaną do warunków miejskich.

EN

To assess the stream hydromorphological conditions number of methods is used. One of them is a method of evaluating flowing waters River Habitat Survey (RHS) being a tool for the detailed description of the river hydromorphological conditions based on the registration of the environment of the river valley. In order to test the applicability of the RHS method to evaluate the hydromorphological conditions of urban rivers selected sections of four rivers flowing through the central part of the Katowice conurbation were investigated. The results show a wide variation. Differences in the results were both between the analyze drivers, as well as within the same stream on sections adjacent to each other. The reasons for this results diversity, except varied river catchment conditions of Silesian cities, should be seen in a small number of factors that strongly influence on the final evaluation indicators and natural habitat transformation. It is advisable to try to use the method Urban River Survey (URS), which is a modified version of the RHS method adapted to urban conditions.

10

Investigation of droughts in the Lankaran region of Azerbaijan

Imanov F. A., Mammadov A. S., Hasanova N. I.

Journal of Water and Land Development

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2012

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no. 16 [I-VI]

11-15

EN

As part of the World Food Program, investigating droughts is within the scope of our interest. Therefore, this paper presents results of studies on droughts in one of the most important economic regions of Azerbaijan. There are different methods to investigate drought. As chosen region is characterised by large precipitation, we preferred to use the SPI method to carry on our study. During the research, dry years were determined according to the seasonal and annual data from weather stations in the province.

PL

Badania suszy jako elementu Światowego Programu Żywnościowego mieszczą się w obszarze naszych zainteresowań badawczych. Niniejszy artykuł przedstawia wyniki badań nad suszą w jednym z najważniejszych gospodarczo obszarów Azerbejdżanu. Istnieją różne metody analizowania suszy. Ponieważ wybrany region charakteryzuje się znacznymi opadami, do badań wybrano metodę standaryzowanego wskaźnika opadu (SPI). Lata suche wyznaczono według sezonowych i rocznych danych, pozyskanych ze stacji meteorologicznych regionu. Analiza opadów z lat 1891-2007 wykazała, że liczba susz w drugiej połowie tego okresu była około 14% większa niż w pierwszej. Co więcej, susze w drugiej połowie były znacznie głębsze i dotkliwsze dla rolnictwa. Wynika to m.in. z faktu, że opady zmniejszyły się o 5-8%. Analizy wykazują, że w ostatnich 5-6 latach dwukrotnie zwiększył się pobór wody w zlewni rzek Lankaran i stale zwiększa się deficyt wody. Susze powodują straty ekologiczne i przyczyniają się do występujących okresowo braków żywności. Jest to więc istotny problem nie tylko przyrodniczy, ale też socjalno-ekonomiczny.

11

Wpływ zrzutów wód kopalnianych na wielkość przepływów wody w rzekach w początkowym okresie odwadniania odkrywki "Tomisławice" KWB "Konin"

Wachowiak G.

Górnictwo i Geoinżynieria

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2011

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R. 35, z. 4

153-166

PL

Odwodnienie odkrywki "Tomisławice" jest od 2009 roku kolejnym czynnikiem antropogenicznym zmieniającym stosunki wodne w zlewni górnej Noteci powyżej jeziora Gopło. Scharakteryzowano przepływy odbiorników wód kopalnianych, którymi są rzeki Pichna i Noteć w okresie poprzedzającym odwodnienie. Omówiono wielkości zrzutów wód kopalnianych według danych KWB "Konin" i poddano je weryfikacji na podstawie prowadzonych pomiarów hydrometrycznych. Porównano zweryfikowane wielkości zrzutów wód kopalnianych z przepływami charakterystycznymi rzek. Określono udział zrzutów w przepływie Pichny i Noteci. Wskazano na konieczność uwzględniania w ocenie wpływu odwodnienia odkrywki "Tomisławice" na odpływ rzeczny i zasoby wodne jeziora Gopło również innych czynników antropogenicznych, jak na przykład zrzuty wód do Noteci z kanału Warta-Gopło. Artykuł powstał na podstawie wyników badań uzyskanych przede wszystkim z monitoringu środowiska wodnego odkrywki "Tomisławice" prowadzonego przez Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy Oddział w Poznaniu we współpracy z Poltegor-Projekt z Wrocławia.

EN

Since 2009, dewatering of the Tomisławice Open Pit has become yet another anthropogenic factor changing hydrographic conditions in the catchment of the Upper Noteć River above Gopło Lake. The flow values of watercourses receiving mine water, i.e. the Pichna and Noteć rivers, recorded in the period before mine dewatering have been analyzed. The values of mine water discharges provided by the Konin Brown Coal Mine are discussed and verified against the results of conducted hydrometric measurements. The verified values of mine water discharge were compared with characteristic values of river flow. The percentage of mine water discharge in the flow of the Pichna and Noteć rivers has been calculated. The necessity to include also other anthropogenic factors such as water discharge from the Warta-Gopło Canal to the Noteć River in the estimates of the impact of the Tomisławice Open Pit dewatering on river discharge and water resources of Gopło Lake is indicated. The paper is based, for the most part, on the results of water environment monitoring of the Tomisławice Open Pit carried out by the Institute of Meteorology and Water Management National Research Institute Poznań Branch in cooperation with the Poltegor-Projekt (Wrocław).

12

Risk assessment of extreme events along the transboundary Mesta River in Bulgaria using integral indices

Diadovski I., Atanassova M., Simeonov V.

Ecological Chemistry and Engineering. S

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2011

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Vol. 18, nr 3

319-332

EN

The present work considers the use of an original integral method for evaluation of the climatic and anthropogenic impacts on the average annual water volume and on the maximum and minimum water flow of Mesta River in the Bulgarian territory. The level of impacts and the respective risk assessment is determined by the index Ki flow module, which accounts for the deviation of the average annual water flow Qi from the flow norm Q0. Another index Mmax,i reflects the deviation of the maximum water flow from the maximum flow norm Qmax,0 and the index Mmin,i considers the deviation of the minimum water flow from the minimum flow norm Qmin,0. In order to assess extreme events (floods, droughts) using the dynamics of the integral indices Mmax,i and Mmin,i, histograms to estimate the frequency of appearance of their values in chosen time intervals were constructed. The function adequately describing the distribution of the frequency of appearance of Mmax,i and Mmin,i is a polynomial of third degree. The new approach offered includes an introduction of more specific indicators for assessing the risk of climatic impacts assessment on the river water flow (Ki, Mmin,i and Mmax,i). This is made for the first time in risk assessment of climatic impacts and has been checked at two monitoring sites from the national monitoring net of Mesta River - Yakoruda site (at the spring of the river) and Khadzhidimovo site (at the Bulgarian/Greek border) for the period 1955-2008. It has to be stressed that the indices are integral in their nature because they reflect specific climatically caused events like abundant water years, dry years, floods and droughts.

PL

Przedstawiono zastosowanie oryginalnej metody oceny wpływu czynników klimatycznych i antropogennych na średni roczny, maksymalny i minimalny przepływ wody w rzece Mesta, płynącej przez terytorium Bułgarii. Wpływ poziomu przepływu i ocena ryzyka jest określany przez wskaźnik Ki modułu przepływu, który uwzględnia odchylenie wartości średniego rocznego przepływ wody Qi od normy przepływu Q0. Indeks Mmax odzwierciedla odchylenie maksymalnego przepływu wody od normy maksymalnej Qmax,0, natomiast indeks Mmin,i określa odchylenie minimalnego przepływ wody od normy minimalnego przepływu Qmin,0. Do oceny częstości występowania zjawisk ekstremalnych (powodzie, susze) w wybranych przedziałach czasu za pomocą indeksów integralnych Mmax,i i Mmin,i, zastosowano histogramy. Funkcją opisującą rozkład częstotliwości występowania Mmax,i i Mmin,i jest wielomian trzeciego stopnia. Proponowane nowe podejście zakłada wprowadzenie bardziej szczegółowych wskaźników oceny ryzyka oddziaływania czynników klimatycznych na przepływ wody w rzece (Ki, Mmin,i i Mmax,i). Metoda została po raz pierwszy wykorzystana do oceny wpływu warunków klimatycznych na przepływ wód rzeki Mesta w punkcie pomiarowym Yakoruda (przy źródle rzeki) oraz w punkcie Khadzhidimovo (na granicy bułgarsko-greckiej). Badania prowadzono w latach 1955-2008. Należy podkreślić, że wskaźniki mają naturę integralną, ponieważ są one wyrazem szczególnych warunkach klimatycznych powodujących lata wilgotne, lata suche, powodzie oraz susze.

13

Stan zasolenia rzeki Odry za kolektorem "Olza" w zależności od jej przepływu i warunków atmosferycznych

Swolkień J.

Górnictwo i Geoinżynieria

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2010

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R. 34, z. 3/1

153-162

PL

W artykule skupiono się na określeniu zależności zasolenia rzeki Odry od jej przepływu i warunków atmosferycznych. Silne zasolenie rzeki jest wynikiem wprowadzania do niej wód kopalnianych odprowadzanych z obszaru południowo-zachodniej części GZW za pośrednictwem kolektora "Olza". W artykule podzielono przepływy na pięć kategorii i przypisano im możliwe do uzyskania klasy czystości ze względu na jony chlorkowe. Na podstawie wyznaczonych za pomocą programu komputerowego "Dyspozytor" marginesów przepływu i na podstawie przynależności rzeki do danej klasy czystości określono, jaki wpływ na stan zasolenia wywiera proces retencjonowania i dozowania wody kopalnianej z kolektora. Ustalono również, w jakich warunkach można dotrzymać najwyższych, a w jakich najniższych norm czystości w rzece ze względu na jony chlorkowe.

EN

This article treats about the state of salinity in Odra river in connection with its flow and atmospheric conditions. Very high chlorides concentration in the river is a consequence of dropping into its water highly contaminated mine waters form the south - western part of Upper Silesian Coal Basin. Mine waters are transported through the interceptor sewer called "Olza". The author divides the river flows on the five categories and classifies them due to the exact water classes. Taking into consideration flow margins calculated by using the computer program called "Dyspozytor" and river absorptiveness due to the specific water class, it was possible to estimate the influence of dosing and retaining on the state of river waters salinity. It was also possible to state in which conditions there is a chance to keep the highest water class and in which there is no such a chance.

14

Assessment of climate impact on the transboundary Struma River flow in Bulgarian territory using integral indices

Davidovski I., Atanassova M., Simeonov V.

Ecological Chemistry and Engineering. A

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2009

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Vol. 16, nr 3

181-200

EN

The present work considers the Struma River on the Bulgarian territory using the integral method for evaluation of climatic and anthropogenic impacts on the river flow average annual water volume and maximum and minimum water flow. The level of this impact is determined by the index Ki (flow module), the index Ci for the deviation of the average annual water flow Qi from the flow norm Q0. the index Ki,max for the deviation of the maximum water flow Qmax,i from the flow norm Q0, the index Ki,min for the deviation of the minimum water flow Qmin,i from the flow norm Q0, the index Mi,max for the deviation of the maximum water flow from the maximum flow norm Qmax,0 the index Mi,min for the deviation of the minimum water flow from the minimum flow norm Qmin,0. The new approach offered includes the introduction of more specific indicators for assessment of climatic impacts on the river water flow like indices for flow module (Ki,av), for deviation of average (Ci), The use of the indices suggested makes possible to estimate the role of different climatic changes by Ki,av, Ki, in, Ki,max. Mi,min, Mi,max, Ci, hi and hi,max. This is made for the first time in assessment of climatic impacts and has been checked at Pernik and Krupnik for the period 1948-2006. The indices are integral in their nature because they reflect specific climatic caused events like abundant years, dry years, floods and draughts.

PL

Dokonano oceny wpływu zmian klimatycznych i antropogennych na średni roczny przepływ wody oraz wartość maksymalnego i minimalnego przepływu wody w rzece Struma przepływającej przez terytorium Bułgarii. Parametry te są określone przez indeks Ki (wskaźnik przepływu), wskaźnik Ci średniego odchylenia rocznego przepływu wody Qi do normy przepływu Q0, indeks Ki,max maksymalnego odchylenia przepływu wody Qmax,i do normy przepływu Q0, indeks Ki,min minimalnego odchylenia przepływu wody Qmin,i do normy przepływu Q0, wskaźnik Mi,max maksymalnego odchylenia przepływu wody do maksymalnej normy przepływu Qmax,0, indeks Mi,min minimalnego odchylenia przepływu wody do minimalnej normy przepływu Qmin,0. Nowe podejście wprowadza bardziej szczegółowe wskaźniki oceny wpływu klimatu na wody rzeki, jak wskaźniki przepływu modułu (Ki,av), odchylenie średniej (Ci), Zastosowanie sugerowanych wskaźników umożliwia ocenę roli różnych zmian klimatycznych przez Ki,av, Ki,min, Ki,max, Mi,min, Mi,max. Ci, hi i hi,max. Metoda ta została zastosowana i sprawdzona w Perniku i Krupniku dla lat 1948-2006 w celu oceny skutków zmian klimatu. Indeksy te odzwierciedlają wywołane zmianami klimatycznymi szczególne wydarzenia, takie jak: lata suche, powodzie i wiatry.

15

Intense precipitation and high river flows in Europe - observations and projections

Kundzewicz Z. W.

Acta Geophysica Polonica

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2005

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Vol. 53, nr 4

385--400

EN

Several destructive floods have occurred in the last decade in Europe, causing record high material damage. The question of detection and attribution of changes in various flood-related indices attracts increasing interest. Among the mechanisms that can impact flood risk are changes in socio-economic systems, which influence terrestrial systems, and changes in the climatic system. The atmosphere's water holding capacity (and hence potential for intense precipitation) increases with temperature and more intense precipitation has been documented in the warming world. However, a general and coherent increase in high river flows has not been detected. Results of change detection studies of daily river flow in Europe show that the overall maxima (for the 1961-2000 period) occurred more frequently in the subperiod 1981-2000 than in the subperiod 1961-1980. Regional changes in the timing of floods have been reported in many areas of Europe, with increasing incidence of late autumn and winter floods (caused by rain) and fewer spring snowmelt floods. Also, the number of ice-jam related inundations has decreased. On the other hand, intensive and long-lasting summer precipitation episodes have led to disastrous floods in Central Europe (cf. the 1997 Odra/Oder flood, the 2001 Vistula flood, and the most destructive 2002 deluge on the Labe/Elbe), and river flooding has been recently recognized as a major hazard in the region. Significant differences between future projections and the reference period, indicating the likelihood of increasing flood hazard, have been identified in both intense precipitation and high flows.

16

Comparison of five depth-averaged 2-d turbulence models for river flows

Wu W., Wang P., Chiba N.

Archives of Hydro-Engineering and Environmental Mechanics

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2004

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Vol. 51, nr 2

183-200

EN

In this study, five depth-averaged 2-D turbulence models for river flows, including the depth-averaged parabolic eddy viscosity model, modified mixing length model, standard k-e turbulence model, non-equilibrium k-e turbulence model and re-normalized group (RNG) k-e turbulence model, are compared in the simulation of flows around a spur-dyke, in a sudden-expanded flume and in two natural rivers. It is shown that in the two field cases where the channel geometries are simple, all five models can give generally good predictions for the main flow features. However, in the two laboratory cases where the channel geometries are complex, differences have been found among these models. The depth-averaged parabolic eddy viscosity model over-predicts the recirculation flows behind the spur-dyke and the flume expansion. The modified mixing length model gives better prediction than the depth-averaged parabolic model. The standard k-e turbulence model predicts well for the recirculation flow in the sudden-expended flume, but under-predicts the length of recirculation zone behind the spur-dyke, while the non-equilibrium and RNG k-e turbulence models provide good results for both laboratory cases.