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2164. Hybrid approach to delineation of homogeneous regions for regional precipitation frequency analysis

Creator:
Gaál, Ladislav, Szolgay, Ján, Lapin, Milan, and Faško, Pavol
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Slovakia, maxima of 1-to-5 day precipitation amounts, calendar year, warm/cold season, regional frequency analysis, homogeneous regions, l-moments, cluster analysis, Slovensko, maximálne 1- až 5-denné úhrny zrážok, kalendárny rok, teplý/chladný polrok, regionálna frekvenčná analýza, homogénne regióny, L-momenty, and zhluková analýza
Language:
Slovak
Description:
Regional frequency analysis of heavy precipitation amounts based on the estimation of the parameters of a regional distribution function using L-moments is adopted for the specific geographical-climatological settings of Slovakia. The paper focuses on the first step of the regional L-moment algorithm (Hosking, Wallis, 1997), which is the delineation of homogeneous regions. Objective and process-based logical pooling techniques are used to form homogeneous pooling groups of rainfall gauging stations for regional frequency analysis of k-day precipitation amounts (k = 1 to 5 days). Even though the delineation of homogeneous regions by means of objective methods is generally accepted and recommended in the literature, it is concluded here that such a pooling of similar sites should not be carried out automatically in precipitation analysis. Instead, a combination of physical/geomorphological considerations and objective methods should be preferred. and Článok sa zaoberá regionálnou frekvenčnou analýzou mimoriadnych úhrnov zrážok, ktorá je založená na odhade parametrov regionálneho rozdelenia pravdepodobnosti pomocou L-momentov a ktorá sa aplikuje v špecifických geograficko-klimatických podmienkach Slovenska. Článok je užšie zameraný na prvý krok tzv. regionálneho L-momentového algoritmu (Hosking, Wallis, 1997), ktorým je vyčlenenie homogénnych regiónov pre k-denné úhrny zrážok (k = 1 až 5). Na formovanie homogénnych zoskupení klimatologických a zrážkomerných staníc sa použila objektívna aj subjektívna (logická) metodika. Napriek tomu, že odborná literatúra všeobecne uznáva a odporúča použiť objektívne postupy na vyčlenenie homogénnych regiónov, v štúdii sme usúdili, že by sa vo frekvenčnej analýze úhrnov zrážok navzájom podobné stanice nemali vyčleňovať automaticky. Namiesto toho odporúčame, aby sa k tomuto účelu použila kombinácia objektívnych postupov, resp. úvah založených na fyzicko-geografických charakteristikách krajiny
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2165. Hybridná metóda pre návrh distribučných systémov rozvodu vody

Creator:
Čistý, Milan and Bajtek, Zbyněk
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
genetic algorithm, linear programming, optimal design of looped hydraulic pipe networks, genetické algoritmy, lineárne programovanie, optimalizácia okruhových sietí rozvodu vody, and hybridná metóda
Language:
Slovak
Description:
A new optimization model for determining the minimum cost for the design of water distribution systems is described in the paper based on a combination of linear programming methodology (LP) and a genetic algorithms approach (GA). The optimal design of looped hydraulic pipe networks belongs to the class of large combinatorial optimization problems that are difficult to handle using conventional operational research techniques. A many different heuristic algorithms have been developed in the last two decades and applied to the design of water distribution systems. Although many research efforts have been made for the sake of achieving the optimal design of the looped water distribution networks, there is still some uncertainty about finding a generally reliable method. The authors of the paper are proposing a method in which the main emphasis is placed on its higher reliability of finding an optimal solution in terms of closeness to a global minimum. In this study the efficiency of GA optimization was improved through a hybrid method, which combines the GA method (heuristic component) with a linear programming methodology (deterministic component). The proposed method was tested on three benchmark least-cost design problems and compared with other methods and the results suggest that the GALP consistently provides better solutions. It was investigated that the method gives results more reliable in terms of closeness to a global minimum. The proposed method guarantees very close convergence to a global optimum. The method is intended for use in the design and rehabilitation of drinking water systems and pressurized irrigation systems as well. and V článku je predstavený model cenovej optimalizácie pri navrhovaní priemerov potrubí okruhových tlakových rozvodov určených na distribúciu vody, ktorý je založený na kombinácii metódy lineárneho programovania (LP) a genetických algoritmov (GA). Cenovo optimálny návrh okruhových sietí patrí do triedy relatívne veľkých kombinatorických problémov, ktoré sú ťažko riešiteľné klasickými technikami matematického programovania. Z tohto dôvodu bolo v posledných dvoch dekádach vyvinutých aj viacero heuristických algoritmov. Napriek tomu pretrváva určitá neistota, pokiaľ ide o spoľahlivosť existujúcich metód, ktorá sa odzrkadľuje ich malým využitím v praxi. Autori predkladajú metódu, v ktorej sa pri hľadaní optimálneho návrhu okruhových sústav v zmysle priblíženia sa ku globálnemu minimu hlavný dôraz kladie na vyššiu spoľahlivosť. Ide o hybridnú metódu, ktorá kombinuje genetické algoritmy (heuristická zložka) s lineárnym programovaním (deterministická zložka). Autori verifikujú metódu na benchmarkovej distribučnej sústave, používanej na testovanie v odbornej literatúre a na dvoch modeloch derivovaných z tejto sústavy so známym riešením. Výsledky potvrdzujú, že v porovnaní s existujúcimi modelmi navrhovaná metóda zaručí vyššiu úroveň kvality dosahovaných výsledkov, tak v zmysle priblíženia sa ku globálnemu minimu, ako aj z hľadiska jednoduchšieho nastavovania parametrov GA a rýchlejšej konvergencie. Metódu možno použiť pri navrhovaní nových systémov aj na rekonštrukciu existujúcich systémov na rozvod pitnej vody a pri navrhovaní tlakových závlahových systémov.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2166. Hydraulic characteristics and sediment generation on slope erosion in the Three Gorges Reservoir Area, China

Creator:
Qian, Feng, Cheng, Dongbin, Ding, Wenfeng, Huang, Jiesheng, and Liu, Jingjun
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
purple soil, runoff, flow hydraulics, sediment, slope gradient, and rainfall intensity
Language:
Slovak
Description:
Hydrological processes play important roles in soil erosion processes of the hillslopes. This study was conducted to investigate the hydrological processes and the associated erosional responses on the purple soil slope. Based on a comprehensive survey of the Wangjiaqiao watershed in the Three Gorges Reservoir, four typical slope gradients (5°, 10°, 15°and 20°) were applied to five rainfall intensities (0.6, 1.1, 1.61, 2.12 and 2.54 mm·min-1). The results showed that both surface and subsurface runoff varied greatly depending on the rainfall intensity and slope gradient. Surface runoff volume was 48.1 to 280.1 times of that for subsurface runoff. The critical slope gradient was about 10°. The sediment yield rate increased with increases in both rainfall intensity and slope gradient, while the effect of rainfall intensity on the sediment yield rate was greater than slope gradient. There was a good linear relationship between sediment yield rate and Reynolds numbers, flow velocity and stream power, while Froude numbers, Darcy-Weisbach and Manning friction coefficients were not good hydraulic indicators of the sediment yield rate of purple soil erosion. Among the three good indicators (Re, v and w), stream power was the best predictor of sediment yield rate (R2 = 0.884). Finally, based on the power regression relationship between sediment yield rate, runoff rate, slope gradient and rainfall intensity, an erosion model was proposed to predict the purple soil erosion (R2 = 0.897). The results can help us to understand the relationship between flow hydraulics and sediment generation of slope erosion and offer useful data for the building of erosion model in purple soil.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2167. Hydrochemical characteristics of Jordan and Yarmouk river waters: effect of natural and human activities

Creator:
Howari, F. M. and Banat, K. M.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
hydrochemistry, Jordan River, Yarmouk River, hydrochémia, rieka Jordán, and rieka Jarmuk
Language:
Slovak
Description:
Water-chemistry was used to assist in understanding the effect of human and natural activities on the Jordan and Yarmouk Rivers. Eighty-eight water samples were collected from different locations along the flow paths of both Jordan and Yarmouk Rivers, and analyzed for major ions. The analyzed water samples of Yarmouk River were predominantly alkaline water with prevailing chloride and sodium; and characterized with low TDS values that range from 571 to 801 mg l-1. The predominant water type of Jordan river is alkaline earth with prevailing chloride and increase portion of alkalies and characterized by high TDS value that range from 2914 to 3224 mg l-1. The sampling took place in different time periods between July 1996 and April 1996 to determine the effect of changing seasons on the chemistry of the studied rivers. From the upper to lower reaches of both Jordan and Yarmouk rivers, a systematic increase of most of the measured major ions concentrations is reported in July 1996. Strong variations were observed in the water chemistry between the different locations. As the distance increase from the mouth of the rivers, so did the salinity of the water. The study found that the Jordan River is affected by groundwater system and the related anthropogenic activities on both sides of the Jordan Valley; where saline groundwater is mainly resulted from ancient entrapped sea water or brine deep seated origin. The water which dilute Yarmouk river is a Ca+2-HCO3-. The in the ion concentrations in 1996 than those reported in 1969 is due to the increase of the anthropogenic effects. and Vplyv antropogénnych aprirodzených faktorov na kvalitu vôd riek Jordán a Jarmuk môže byt hodnotený aj pomocou hydrochemických analýz. Pozdlž tokov Jordán a Jarmuk bolo odobratých a analyzovaných 88 vzoriek vody. Vzorky vody rieky Jarmuk boli prevažne alkalické s prevládajúcimi iónmi chlóru a sodíka, charakterizované nízkymi hodnotami celkovej mineralizácie (TDS), ktorá bola v rozmedzí 571 - 801 mg l-1 . Voda v rieke Jordán je prevažne alkalická s dominantnými chloridmi a zvýšeným podielom alkalických iónov s vysokou TDS v rozmedzí 2914 - 3224 mg l-1 . Vzorky vody boli odobraté v case medzi aprílom a júlom 1996, aby sa dala urcit zmena chemizmu tokov pocas roka. Pocas júla 1996 bola zistená v oboch tokoch od pramena po ústie zvyšujúca sa koncentrácia sledovaných iónov. Medzi jednotlivými lokalitami boli zaregistrované velké rozdiely v koncentráciách sledovaných prvkov. Výskumom sa zistilo, že rieka Jordán je ovplyvnená podzemnými vodami aantropogénnou cinnostou na oboch brehoch. Slané podzemné vody sú dôsledkom predovšetkým dávneho záchytu morskej vody, a existencie solných vrstiev v povodí. Zmeny v koncentrácii iónov v riekach medzi rokmi 1969 a 1996 môžu byt dôsledkom antropogénnej cinnosti.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2168. Hydrodynamic investigation and numerical simulation of intermittent and ephemeral flows in semi-arid regions: Wadi Mekerra, Algeria

Creator:
Korichi, Khaled and Hazzab, Abdelkrim
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
semi-arid, temporary flows, Wadi Mekerra, flood wave, Saint-Venant equations, finite volume, shock capturing, semi-aridný, občasné povodne, povodňová vlna, rovnice SaintVenanta, konečný objem, and pohltenie nárazu
Language:
Slovak
Description:
Semi-arid regions are characterized by important infrequent rainfall. They often occur in early autumn and give rise to devastating floods. Flooding problems at Wadi Mekerra, located in the Sidi Bel Abbes town (Northwest Algeria), was traditionally the main concern of researchers and government officials. In this work, the magnitude of raging flood wave in the studied catchment and the principal causes are discussed. After this, we present the main hydromorphometric features and the results of numerical simulations of flood wave. This simulation is done by using finite volume shock capturing schemes. It concerns applying the first order Godunov scheme and the second order Monotonic Central scheme. The Manning roughness coefficient was used as a calibration parameter. The comparison of numerical results with observed data confirms more stability and accuracy of applied numerical schemes in rising limb phase than in the falling limb phase. These results provide information on flood forecasting and monitoring of changes in the magnitude of the flow in Wadi Mekerra. and Semiaridné oblasti sú charakterizované významnými občasnými dažďami. Vyskytujú sa spravidla v jeseni a spôsobujú devastačné povodne. Povodne vo Wadi Mekerra v meste Sidi Bel Abbes (severozápadné Alžírsko) sú často problémom pre výskumníkov a vládnych úradníkov. Práca analyzuje devastačné povodne v tomto povodí. Okrem toho sa uvádzajú najdôležitejšie hydromorfomertrické charakteristiky a výsledky simulácií povodňovej vlny. Simulácia je aplikáciou Godunovovej schémy prvého rádu a Monotonickej centrálnej schémy druhého rádu. Ako kalibračný parameter bol použitý Manningov súčiniteľ drsnosti. Porovnanie simulovaných a pozorovaných údajov potvrdzuje väčšiu stabilitu a presnosť počas rastúcej vetvy prietokovej vlny, ako je tomu v klesajúcej fáze. Tieto výsledky sú informáciou o možnostiach predpovede a monitoringu povodní vo Wadi Mekerra.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2169. Hydrodynamic modeling of stratified estuary: case study of the Jadro River (Croatia)

Creator:
Ljubenkov, Igor
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
estuary, salinity, numerical model, box model, Jadro, and Croatia
Language:
Slovak
Description:
The Jadro River with total length of 4.3 km and average annual discharge of 7.9 m3 s-1 is a relatively small river on the east coast of the Adriatic Sea, close to Split. Field campaign measurements were made to estimate salt intrusion in the Jadro estuary in July 2012. This measurement confirmed the stratified character of the estuary where fresh water flows in a thin layer over denser sea water. Furthermore, a numerical model was set up for simulating unsteady stratified flow without mixing between the layers. The model is applied for the Jadro River and field measurements are used for calibration. In addition, the steady state of stratification within the estuary is analyzed by a box model which assumes mixing between layers. Results of the numerical and the box models were compared. The flushing time estimated with the box model is approximately 1.5 day for summer steady conditions. Numerical analysis however shows that the residence time is much larger owing to flow unsteadiness.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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