Wyniki wyszukiwania - Biblioteka Nauki

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Dominant discharge in the Indus river from downstream of the Kotri barrage dam

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Radecki-Pawlik A. , Laszek W. , Plesinski K. , Khan Lashari B.

Acta Scientiarum Polonorum. Formatio Circumiectus

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2014

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tom 13

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nr 4

EN

Hydraulic data of the Indus River, downstream of Kotri Barrage dam are analyzed. An attempt has been made to determine the dominant discharge, which is defined as that discharge which over a long time period transports the most sediments and could be used to predict the shape of river cross-section. For dominant discharge calculation Wolman and Miller’s approach has been applied. Since the transport of sediment concentration could be a more effective variable for forming the shape of the river cross-section, suspended sediment concentration has been introduced, because more than 85% of total load is in suspension. We show in the paper that water discharge Q = 1000 m³ · sˉ¹ of water is a frequent discharge and carries maximum sediment load. This discharge we call here the dominant discharge (Qdd) for the Kotri dam cross section.

PL

W pracy określono wartość przepływu korytotwórczego dla rzeki Indus w przekroju zapory Kotri Barrage. Wykonano próbę analizy przepływu dominującego jako tego, który jest zdefiniowany jako trwający przez długi okres oraz transportujący największą ilość rumowiska i może być stosowany do przewidywania kształtu przekroju poprzecznego rzeki. Do obliczenia przepływu korytotwórczego zastosowano metodę Wolmana and Miller. Wykazano, że przepływ wody Q = 1000 m³ · sˉ¹ wody jest wartością, przy której następuje maksymalny przepływ rumowiska. Ten przepływ określa się jako przepływ dominujący (Qdd ) w przekroju zapory Kotri Barrage.

2

Sediment transport and water quality in Machovo Lake [Czech Republic]

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Dostal T. , Krasa J. , Vrana K. , Dockal M. , Koudelka P. , David V. , Vokurka A.

Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation

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2010

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tom 42

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nr 1

139-148

EN

Máchovo Lake is a historical reservoir founded by Czech King Charles IV. in 14th century. Located in northern part of central Bohemia it has been widely used for recreation purposes for many decades (or even centuries). Its catchments (ca 100 sq km) consist of intensively used agricultural land (ca 25% of area) and of large forested area under nature protection. Several other lakes (ponds) are chained on the two reservoir’s inlets. Irrespective of its great recreation potential Máchovo Lake is one of the Bohemian lakes known for its problems with eutrophication and water quality. The project was set up to point out sources of nutrients and to search for proper solutions. Sediment loads in every lake within the catchments were measured and sampled in order to quantify the nutrients and other pollution. Point and non point sources of phosphorus and other nutrients were searched. Sediment transport within catchments was modelled using WaTEM/SEDEM model. Interestingly, the water quality in the particular ponds varies signifi cantly even though each one of several hundred years old ponds is heavily silted. Soil erosion protection measures within catchments were proposed altogether with flood protection measures in the stream valleys and waste water treatment facilities in surrounding villages. Setting up water quality sampling devices in selected stream profi les was tested and designed. The continual proper management should lead to water quality improvement.

PL

Położone w północnych Czechach Jezioro Máchovo jest zbiornikiem dla celów rekreacyjnych zbudowanym w XIV wieku przez czeskiego króla Karola IV. Jego zlewnia o powierzchni 100 km2 jest w 25% intensywnie użytkowana rolniczo, a pozostały zalesiony obszar podlega ochronie. Jakość wody i eutrofizacja wód jeziora oraz towarzyszących mu silnie zamulonych stawów stanowi poważny problem ekologiczny. Celem badań było określenie punktowych i powierzchniowych źródeł dostawy składników pokarmowych i rozwiązanie tego problemu. Do oceny dostawy sedymentu zastosowano WaTEM/SEDEM model. Została zaproponowana przeciwpowodziowa i przeciwerozyjna ochrona gleby przed erozją oraz gospodarka ściekami w obrębie zlewni. Działania te powinny doprowadzić do polepszenia jakości wody.

3

Forecasting suspended sediment load using regularized neural network: Case study of the Isser River (Algeria)

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Tachi S. E. , Ouerdachi L. , Remaoun M. , Derdous O. , Boutaghane H.

Journal of Water and Land Development

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2016

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tom no. 29

75--81

EN

In the management of water resources in different hydro-systems it is important to evaluate and predict the sediment load in rivers. It is difficult to obtain an effective and fast estimation of sediment load by artificial neural network without avoiding over-fitting of the training data. The present paper comprises the comparison of a multi-layer perception network once with non-regularized network and the other with regularized network using the Early Stopping technique to estimate and forecast suspended sediment load in the Isser River, upstream of Beni Amran reservoir, northern Algeria. The study was carried out on daily sediment discharge and water discharge data of 30 years (1971–2001). The results of the Back Propagation based models were evaluated in terms of the coefficient of determination (R2) and the root mean square error (RMSE). Results of the comparison indicate that the regularizing ANN using the Early Stopping technique to avoid over-fitting performs better than non-regularized networks, and show that the overtraining in the back propagation occurs because of the complexity of the data introduced to the network.

PL

Ocena i przewidywanie ładunku zawiesiny w rzekach są istotne w zarządzaniu zasobami wodnymi w różnych hydrosystemach. Trudno jest uzyskać efektywne i szybkie oszacowanie ładunku zawiesiny za pomocą sztucznych sieci neuronowych bez uniknięcia przepełnienia danymi. W niniejszej pracy porównano wyniki zastosowania wielowarstwowej sieci w dwóch wariantach – sieci nieregularyzowanej i sieci regularyzowanej z użyciem techniki Early Stopping do oceny i prognozowanie ładunku zawiesiny w rzece Isser powyżej zbiornika Beni Amran w północnej Algierii. Badania bazowały na notowaniach dobowego odpływu zawiesiny i danych dotyczących odpływu wody w ciągu 30 lat (1971–2001). Wyniki modeli opartych na metodzie wstecznej propagacji oceniono za pomocą współczynnika determinacji (R2) i pierwiastka ze średniego błędu kwadratowego. Porównanie wyników dowodzi, że sieć neuronowa regularyzowana przy pomocy techniki Early Stopping celem uniknięcia przeładowania sprawdza się lepiej niż sieć nieregularyzowana. Wyniki wskazują, że przeładowanie wstecznej propagacji ma miejsce z powodu złożoności danych wprowadzonych do sieci.

4

Dynamics of suspended sediment load with respect to summer discharge and temperatures in Shaune Garang glacierized catchment, Western Himalaya

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Kumar R. , Kumar R. , Singh S. , Singh A. , Bhardwaj A. , Kumari A. , Randhawa S. S. , Saha A.

Acta Geophysica

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2018

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tom Vol. 66, no. 5

1109--1120

EN

The observed and predicted rise in temperature will have deleterious impact on melting of snow and ice and form of precipitation which is already evident in Indian Himalayan Region. The temperature-dependent entities like discharge and sediment load will also vary with the observed and predicted rise posing environmental, social and economic threat in the region. There is little known about sediment load transport in relation to temperature and discharge in glacierized catchments in Himalaya mainly due to the scarcity of ground-based observation. The present study is an attempt to understand the suspended sediment load and transportation in relation to variation in discharge and temperature in the Shaune Garang catchment. The result shows strong dependence of sediment concentration primarily on discharge (R2 = 0.84) and then on temperature (R2 = 0.79). The catchments with similar geological and climate setting were observed to have comparatively close weathering rate. The sediment load was found to be higher in the catchments in eastern and central part of Indian Himalayan Region in comparison with western part due to dominance of Indian Summer Monsoon leading to high discharge. The annual physical weathering rate in Shaune Garang catchment was found to be 411 t km−2 year−1 which has increased from 327 t km−2 year−1 in around three decades due to rise in temperature causing increase in discharge and proportion of debris-covered glacierized area.

5

Developing nonlinear models for sediment load estimation in an irrigation canal

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Ahmed F. , Hassan M. , Hashmi H. N.

Acta Geophysica

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2018

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tom Vol. 66, no. 6

1485--1494

EN

The study was performed to estimate the weekly sediment load in Thal canal located in Mianwali district Punjab, Pakistan. Past records of sediments and discharge have been considered as the input parameters. The best input combinations have been identified with the help of advanced algorithms including full, sequential and increasing embedding, genetic algorithm and hill climbing in combination with the gamma test. Model training has been carried out using two artificial neural networkbased algorithms, namely Broyden–Fletcher–Goldfarb–Shanno (BFGS), back-propagation and a local linear regression technique. A variety of statistical parameters including R square, root mean squared error, mean square error and mean bias error (MBE) has been calculated in order to evaluate the best models. The results strongly suggested that BFGS-based model performed better than all other models with remarkably low values of MBE. Significantly high values of correlation coefficient (R square) in both training and testing evidenced a close similarity between actual and predicted sediment load values for the same model.

6

Ecohydrological status of Lake Tana – a shallow highland lake in the Blue Nile (Abbay) basin in Ethiopia: review

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Ligdi E. E. , El Kahloun M. , Meire P.

International Journal of Ecohydrology and Hydrobiology

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2010

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tom 10

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nr 2-4

EN

This paper is based on a country report for Ethiopia prepared as a part of the ecohydrology component of IHP UNESCO’s FRIEND/Nile-phase II Project. It reviews past and current research in the Lake Tana sub-basin around the lake. The objective of the study was to determine the ecohydrological status of the Lake as a tool for integrated water resource management in improving the sustainability of the quantity and quality of freshwater resources in the Nile basin. The preliminary results show that reduced lake water level with its annual fluctuations and seasonal floods associated with high flows are becoming amplified and frequent, and the total average annual sediment load of the four major tributaries shows an increasing trend. Source pollution from urban waste and rural agriculture, and degradation of biota in the catchment are the two main environmental threats for the lake ecosystem. Knowledge gaps were identified and future research needs were recommended along with suggestion of some potential phytotechnologies to be applied in the study area.

7

The changing sediment loads of the world’s rivers

80%

Walling D. E.

Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation

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2008

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tom 39

EN

This contribution reviews available evidence of recent changes in the sediment loads of the world’s rivers and identifi es the key drivers of such change. Land clearance, land use change and other facets of catchment disturbance, soil conservation and sediment control programmes and dam construction are shown to have resulted in signifi cant recent changes in the sediment loads of many world rivers. Some rivers have been characterized by signifi cant increases in sediment load, whereas others show signifi cant decreases. Interpretation of the resulting trends requires consideration of aggregation and storage and buffering effects within a river basin, such that the downstream response of a river may not clearly refl ect the changes occurring in the upstream basin and in the loads of tributary rivers.

PL

W artykule przedstawiono dostępne informacje wskazujące na aktualne zmiany w ładunku rumowiska rzek świata oraz wskazano na podstawowe czynniki powodujące te zmiany. Wycinanie lasów, zmiany użytkowania terenu, a także inne działania związane zarówno z degradacją, jak i ochroną gruntów, oraz programy redukcji erozji gleb i budowa zapór, znacząco wpływają na ładunki rumowiska wielu rzek świata. Niektóre rzeki charakteryzują się znaczącym wzrostem ilości rumowiska, podczas gdy inne wskazują na znaczący ich spadek. Interpretacja wynikowych trendów wymaga rozważenia czynników mających cechy oddziaływania zagregowanego, opóźnionego i buforującego z całej zlewni, jako że informacje z ujściowych odcinków rzek nie w pełni odzwierciedlają zmiany zachodzące w górnej części rzeki i w jej dopływach.