نشریه پژوهش های مهندسی آب ایران
سال دوم شماره 3 (پیاپی 4، پاییز 1402)

The correct and accurate estimation of the river flow using different models is a significant issue in water resources research. In this research, two hydrometric stations of Sari-Qomish and Nizam-Abad located in West Azarbaijan province were used to accurately estimate the daily flow of Zarineh-Rood River. To reach this aim, Empirical Mode Decomposition (EMD) preprocessing algorithm was used to deal with the complexity and instability of time series data. EMD is a data analysis method for extracting signals in data generation through non-linear and non-stationary operations. In this research, the method of gene expression programming model and artificial neural network model were used. The results of the research showed that the performance of the gene expression programming model was equal and sometimes less than the performance of the artificial neural network. However, the combination of the two mentioned models with the technique (EMD) increased the accuracy of the model and reduced the error in simulating the river flow in Sari-Qomish and Nizam-Abad stations.

Khuzestan province, one of water-rich provinces of Iran, is the crossing point of several important rivers, and the protection of the quantity and quality of these water resources is the most important concerns of water science thinkers and researchers. Recently, the emergence of numerous problems, often associated with human intervention, has endangered the health of these valuable resources. In this article, the data and field observations were analyzed to detect the important water problems created related to the Gatvand dam, the salinity of the Karun River, the three Karun dams, water transfer between water basins, the design of the Bahmanshir system, and Chamshir dam dewatering.  Finally, suggestions were presented to prevent or reduce the effects of improper exploitation of the mentioned plans.

Floods are natural events that cause significant morphological changes in riverbeds and adjacent lands. Therefore, predicting the process of river changes under overbank flows is one of the important issues in river engineering. Conducting laboratory studies, in addition to time, requires high cost and accuracy, so using a numerical and analytical model is more reliable and requires less cost due to providing accurate results. In this study, the behavior and hydraulic geometry of the trapezoidal compound channel have been investigated using MIKE 21 software for the type of bankfull and overbank flow. First, the compound trapezoidal channel section with erodible boundaries was developed under bankfull flow, and then the behavior and geometry of the developed trapezoidal channel were evaluated under overbank flows. The results showed that when the cross-section of the channel is full of water, there was no significant change in the width of the main channel, but the width of the main channel in overbank flows is higher than the full section and increases rapidly. The mean relative differences obtained at the upstream and downstream width of the trapezoidal section and flow depth are 0.96, 0.88, and 0.98, respectively. The width, depth, and sediment concentration values predicted by the above software are better estimated than those of stabable channel design methods such as Brownlie, Van Rijn, and WBP.

Recognizing a problem is a crucial step when it comes to tackling any issue in policymaking. In the context of environmental and water-related concerns, Iran faces a persistent challenge regarding the management of the Hirmand/Helmand transboundary river basin shared with Afghanistan. This paper focuses on examining the water-related problems that arise from the utilization of shared resources between Iran and Afghanistan, with a particular emphasis on the Sistan region. The objective is to analyze the various factors contributing to the vulnerable state of Sistan. A "Matrix of Sistan's Water Issues" is presented, utilizing a descriptive-explanatory approach and drawing on a wide range of library sources. This matrix a range of concerns on water problems at the local, provincial, national, and international levels that interact with each other in three areas of environment and climate, agriculture, and household in a complex manner. When examining the international aspect of the water issues in Sistan, this article highlights the internal conditions of Afghanistan and its water management practices, as well as the construction of otherized social identity aimed at nation-state building. Additionally, the involvement of third-party states, motivated by their own interests, has emerged as a significant factor influencing the current state of affairs in Sistan. Given the crucial importance of water for Afghan society and its leaders, it is not surprising that third-party states aiming to exert influence over Afghanistan are aware of this reality. Consequently, third-party states are pursuing infrastructure projects within the Hirmand river basin to benefit themselves, even if it comes at the expense of social changes in Iran's Sistan region.

Erosion occurs naturally in riverbeds. The high cost and limitations of physical models have led to using mathematical and numerical models. In this research, the two-dimensional mathematical model CCHE2D was applied for the simulation of sediment transport in Saqqez River flows throughout the Kurdistan province to determine the rate of erosion and sedimentation. The Study area includes the main and sub-branches that intersect at the site of Tamogheh village. After analyzing the sensitivity of the model, the model proposed by Wu et al. with a Root Mean Square Error of 0.002 and Mean Absolute Error Percentage of 7.14 was used as the most appropriate relationship for calculating sediments. Finally, it was found that on average, in the study period, sediment deposition was about 82485 cubic meters, erosion was about 18708 cubic meters, and average bed level changes were 0.20 meters. The Khan tributary accounted for 63% of the total erosion of the study period.

The multi-dimensionality of the flood phenomenon causes us to not be able to get an accurate estimation of flood characteristics with one-variable analysis. Moreover, multi-dimensional analysis usually includes the variables of peak flow, volume, and duration of flood. Meanwhile, other variables, such as sediment, can affect the occurrence of floods. This research examined the effect of sediment on the occurrence of floods using copula functions of two variables of volume and flood sediment in the Qarasu River catchment in a statistical period of 41 years. The results revealed that the Weibull distribution is the most suitable marginal distribution, and the Frank copula function can well create the bivariate distribution of volume and flood sediment. Furthermore, the estimated return period of the bivariate showed that the sediment parameter has a significant effect on the return period. However, it is decreased in the case of {or} and increased in the case of {and}.