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The main objective of the present study was to investigate runoff response to climate variables as well as landuse change over the past 30 years in Tajan River Basin, using the SWAT model. After the model calibration, four different scenarios were simulated and compared. Comparison of simulated runoff results determined from different scenarios indicated that climatic variables reduced the amount of runoff while the landuse change increased this amount in most months of the year. Simulated runoff under three landuse scenarios in all months demonstrated that the runoff achieved from scenario 1 was smaller than scenarios 2 and 4. In scenario 4, the runoff amount increased by 3–21% and 0.8–13% in Kordkheil station compared to those of scenario 1 and scenario 2, respectively. Furthermore, the increase in runoff for scenario 4 is 3–19% and 2–12% in Rig Cheshmeh station relative to those of scenario 1 and scenario 2, respectively. Nonetheless, the maximum change in runoff was only 6% under climatic variables. Hence, landuse had more significant impacts on the runoff compared to climatic variables.

This study investigated the effectiveness of a new method of reducing scour in river bends. In this method, a perforated tube was placed along the bend on the bed and water and air were separately injected into the bend flow from both ends of the tube. The goal was to make a water and air screen to block secondary flows and prevent them from reaching the outer bank. The air jet and water jet injection modes changed the location of maximum scour depth from the outer wall to the middle of the bend, which increased the navigable width. Increasing the spacing between tube ports decreased the maximum scour depth. A port spacing of 5 cm was determined to be the optimal amount. At a bend section of 90°, the decrease in maximum scour depth was estimated to be 85% and 91% under air jet injection (qa/Q = 2.74) and water jet injection (qw/Q = 0.17), respectively. At 170°, the decrease in maximum scour depth was 79% and 86% for the air jet and water jet, respectively. The results show that the optimal effect was obtained by water jet injection.

The aim of this study is to improve the performance of the shuffled complex evolution (SCE) algorithm used in the optimization of hydropower generation in reservoirs as a complex issue in water resources. First, the SCE algorithm is merged with the differential evolution (DE) algorithm to form the SCE-DE algorithm. Then, a complex mathematical function is used as a benchmark to evaluate the performance and validate the SCE-DE algorithm and the outcomes are compared with the original SCE algorithm to show the superiority of the proposed SCE-DE algorithm. In addition, the two-reservoir system of Dez-Gotvand is considered as a real optimization problem to evaluate the performance of the SCE-DE algorithm. It is revealed that optimization by SCE-DE is much better than SCE. In conclusion, the results show that the proposed SCE-DE algorithm is a reasonable alternative to optimizing resource systems and can be used to solve complex issues of water resources.

Agricultural water resources are scarce in Iran, and agricultural water management is essential to overcome this limitation. Determination of the water productivity index (WP) using the methods of optimization of cropping patterns and optimal water allocation is the most effective tool in water management in the agricultural sector. In this study, a non-linear optimization model was used to calculate the maximum WP in the Qazvin plain irrigation network. The proposed model was applied to six different water supply scenarios including 100% and 90%, 80%, 70%, 60%, and 50% of full irrigation volume. The results showed that the scenario of 60% of full irrigation could increase the WP index by 8.5%, while with the implementation of this scenario, the net benefit from the sale of agricultural products was reduced to the amount of 247 × 109 Iranian Rials (IRR), which was 28% less than the existing conditions in the region. Therefore, the 60% water supply was selected as the economical and efficient scenario in the irrigation of Qazvin plain. It can be claimed that the most important index in agricultural water management is the WP index.