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1

Stream flow dynamics under current and future land cover conditions in Atsela Watershed, Northern Ethiopia

Gebretekle Haftu, Nigusse Amare Gebremedhin, Demissie Biadgilgn

Acta Geophysica

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2022

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Vol. 70, no 1

305--318

EN

The aim of the present study was to detect land cover change for the last three decades and estimate its impact on stream flow dynamics under the current and future scenarios. Landsat satellite imageries were used for land cover classification for selected years (1987, 2002 and 2017). The effect of land cover change on stream flow was evaluated using SWAT model, and its performance was tested. The findings indicated significant land cover changes in the last three decades. Coverage of cultivated land (17%) and bare land (1%) in 1987 increased rapidly to 43 and 17% in 2017. Furthermore, there was 70% agreement between observed and simulated stream flow in both the calibration and validation phases. The stream flow of the watershed was changing significantly in response to land cover dynamics. The evaluation of hydrological response due to land cover change showed a monthly mean stream flow decrease by 12.7 m3 /s (−38%) in 1987 and 2017 in dry months. Nevertheless, it showed a monthly mean stream flow increase by 53.06 m3 /s (23%) in wet months. Similarly, between the years 2017 and 2047, the stream flow was estimated to increase by 42.84 m3 /s (15%) for wet months and a decrease by 13.52 m3 /s (−66%) for dry months. Generally, it can be concluded that land cover changes have significant impact on stream flow. Hence, establishing strong land use and water resource policies is an essential means for better evaluation and monitoring of water resource in the study area.

2

Complexity analyses of Godavari and Krishna river streamflow using the concept of entropy

Singh Rahul Kumar, Jain Manoj Kumar

Acta Geophysica

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2021

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Vol. 69, no. 6

2325--2338

EN

The hydrological regime in both the Godavari and Krishna River has been altered due to both human-induced and environmental changes. The present study utilizes the sample entropy and its more generalized approach known as multiscale entropy to investigate the temporal and spatial distribution of complexity and quantify them using SampEn values. Daily streamflow for five stations, three from Godavari River (Dhalegaon, Nowrangpur, and Polavaram), and two from Krishna River (Yadgir and K. Agraharam), was analysed for the complexity analyses. Trends in the streamflow for the selected gauging stations and their annual entropy values have also been evaluated using the Mann–Kendall test. The trend results revealed that three (Dhalegaon and Nowrangpur in Godavari basin and Yadgir in Krishna basin) out of five stations showed significant decreasing trends for both monthly and annual streamflow series. The declining trend in streamflow could be attributed to both anthropogenic (reservoir operation, increased water abstraction, etc.) and climatic (change in monsoon rainfall, temperature, etc.) factors. The most significant reduction in annual streamflow during the post-impact period was observed at Dhalegaon station in Godavari Basin (from 53,573 to 19,555 m3/s) signifying maximum alteration in annual flow regime. The entropy analysis results of streamflow showed that there was obvious spatial and temporal variation in the complexity, as indicated by the annual SampEn values. Although not profound, a negative correlation exists between the annual runoff and SampEn values (highest −0.42 at K. Agraharam) and hence a reverse correspondence exists between them. In MSE analysis, the original streamflow series increased with time scale (up to 30 days was chosen for this study), whereas entropy decreased with an increased time scale. Due to the fully operational state of the dams upstream of the gauging stations, the entropy values during the post-impact period were less the pre-impact period. The present study can be used as a scientific reference to use information science to detect hydrologic alterations in the river basins. Future studies should focus on considering both climatic and land-use changes in conjunction with the human-induced changes for more comprehensive river system disorder analysis.

3

Discriminating Between Different Streamflow Regimes by Using the Fisher-Shannon Method : An Application to the Colombia Rivers

Pierini J. O., Restrepo J. C., Lovallo M., Telesca L.

Acta Geophysica

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2015

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Vol. 63, no. 2

533--546

EN

The Fisher-Shannon (FS) information plane, defined by the Fisher information measure (FIM) and the Shannon entropy power (NX), was robustly used to investigate the complex dynamics of eight monthly streamflow time series in Colombia. In the FS plane the streamflow series seem to aggregate into two different clusters corresponding to two different climatological regimes in Colombia. Our findings suggest the use of the statistical quantity defined by the FS information plane as a tool to discriminate among different hydrological regimes.

4

Modelowe badania przepływu podczas obróbki strumieniem wodnym

Szczepanik M.

Prace Naukowe Katedry Budowy Maszyn / Politechnika Śląska

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2009

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nr 1

217-236

PL

Artykuł przedstawia przebieg procesu modelowania oraz otrzymane wyniki zjawiska przepływu strugi wodnej przez dyszę wodną głowicy tnącej maszyny do obróbki strumieniem wodno-ściernym. Celem badań była analiza zachowania się strugi wodnej wewnątrz dyszy oraz w powietrzu po jej opuszczeniu, a także określenie współczynników jej rozbicia.

EN

The article presents course of modeling process and recived results of pure water flow through waterjet nozzle. The purpose of research was the analysis of waterjet behaviour inside nozzle channels and in the air, after it leaves the nozzle. Finally, extension factor of waterjet was determined.

5

The vortex dynamics in HTc superconductor in external magnetic field

Sosnowski J.

Journal of Technical Physics

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2005

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Vol. 46, no 4

245-255

EN

The penetration of magnetic induction into HTc superconductors has been considered taking into account the layered structure of these materials. For magnetic field parallel to the planes a one-dimensional penetration has been considered, while in perpendicular magnetic field it is a two-dimensional problem. The flux creep equation has been considered, whose solution was confirmed by experimental data measured on an Y-Ba-Cu-O sample. The magnetic diffusion equation has been solved for a description of the magnetic induction profiles in an increasing external magnetic field. The dynamic anomalies of the current-voltage characteristics have been then predicted, in agreement with experimental observations. The model taking into account the influence of the vortex-pinning center interaction on the magnetic field dependence of the critical current, has been also applied successfully for description of the anomalies.

6

Wpływ czasu przepływu strumienia produktów przez pętlę zwrotną na generację chaosu w reaktorze autotermicznym

Berezowski M., Grabski A., Iwanowski J.

Inżynieria Chemiczna i Procesowa

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2001

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T. 22, z. 3B

241--246

PL

Praca niniejsza zawiera analizę teoretyczną wpływu czasu opóźnienia wnoszonego przez pętlę cieplnego sprzężenia zwrotnego na generację złożonej dynamiki rurowego reaktora autotermicznego. Wykazano możliwość wystąpienia chaosu w powyższym układzie.

EN

The present study deals with a theoretical analysis of the effect of delay time of heat transfer upon the generation of complex dynamics in a heat integrated tubular reactor. The importance of this time for the presence of chaos in a system is demonstrated.