In this work, an optimal design of a water distribution network is proposed for large irrigation networks. The proposed approach is built upon an existing optimization method (NSGA-II), but the authors are proposing its effective application in a new two-step optimization process. The aim of the paper is to demonstrate that not only is the choice of method important for obtaining good optimization results, but also how that method is applied. The proposed methodology utilizes as its most important feature the ensemble approach, in which more optimization runs cooperate and are used together. The authors assume that the main problem in finding the optimal solution for a water distribution optimization problem is the very large size of the search space in which the optimal solution should be found. In the proposed method, a reduction of the search space is suggested, so the final solution is thus easier to find and offers greater guarantees of accuracy (closeness to the global optimum). The method has been successfully tested on a large benchmark irrigation network.

During last twenty years, a number of extremely dry years have occurred in a number of European river basins. In Slovakia, the lowland streams of southern Slovakia have been particularly affected by drought. One of these streams is the Ipeľ River. In this basin we have three continuous observations of daily flows since 1931: from Krupinica at Plášťovce, Litava at Plášťovce, and from Ipeľ at Holiša station. The first part of the paper is devoted to the statistical analysis of the Litava flow series. In the second part, the hydrological balance in the Litava basin for the three subperiods (1931-1960, 1961-1990, and 1991-2020) in annual time step has been elaborated. The first thirty years 1931-1960 were the wateriest (runoff was 205 mm). In the last thirty years, the runoff coefficient was only 0.2 (runoff 131 mm) in Litava basin. In the final part of the study, the BILAN balance model (in a monthly step) was used to compute the contribution of several runoff components in the Litava basin during period 1930/31-2019/20. The long-term average baseflow accounts for 40.7% of the total modelled runoff, interflow accounts for 46.8% and direct runoff accounts for 12.5% of the total modelled runoff.

River water temperature is important in many environmental applications, hydrology, and ecology research. It mainly depends on several parameters of water bodies such as streamflow, groundwater interactions, and their surrounding atmosphere. It has been correlated with air temperature as a substitute due to the ease of applicability for rivers with some limitations over detailed meteorological data. An evaluation of integrated river water temperature and streamflow fluctuations is proposed to evidence biological activity, chemical specimen, oxygen solubility, self-purification capacity of a river system, and variation of flows due to hydro-climatic changes. The possibility of predicting the river water temperature at various locations over a river basin is vital for water quality management. Modelling of river water temperature is usually based on a suitable mathematical model and field measurements of various atmospheric factors. The aim of the study is the analysis and subsequent simulation of monthly and daily water temperatures in the Litava River at the Plášťovce station. First of all, the statistical analysis of a series of daily values of Litava water temperature and air temperature (Bzovík meteorological station) was done. In the second part of the study, the several multi-regression models of the daily water temperatures are analyzed.

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 optimál-neho návrhu okruhových sústav v zmysle priblíženia sa ku globálnemu minimu hlavný dôraz kladie na vyš-šiu spoľahlivosť. Ide o hybridnú metódu, ktorá kombinuje genetické algoritmy (heuristická zložka) s lineár-nym programovaním (deterministická zložka). Autori verifikujú metódu na benchmarkovej distribučnej sús-tave, 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. 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 guarante...

There are many problems related to pipe network rehabilitation, the main one being how to provide an increase in the hydraulic capacity of a system. Because of its complexity the conventional optimizations techniques are poorly suited for solving this task. In recent years some successful attempts to apply modern heuristic methods to this problem have been published. The main part of the paper deals with applying such technique, namely the harmony search methodology, to network rehabilitation optimization considering both technical and economic aspects of the problem. A case study of the sprinkler irrigation system is presented in detail. Two alternatives of the rehabilitation design are compared. The modified linear programming method is used first with new diameters proposed in the existing network so it could satisfy the increased demand conditions with the unchanged topology. This solution is contrasted to the looped one obtained using a harmony search algorithm