The paper presents the results of an experimental study carried out to investigate the effect of geometric and hydraulic parameters on energy dissipation and location of the hydraulic jump, with a change in the height of roughness elements and the divergence of walls in different discharges. Experiments were conducted in a horizontal rectangular basin with gradual expansion 0.5 m wide and 10 m long. Four physical models were fixed in the flume. The measured characteristics of the hydraulic jump with different divergences ratio (B = b₁/b₂ = 0.4, 0.6, 0.8, 1) and the inflow Froude numbers (6 < Fr₁ < 12) were compared with each other and with the corresponding values measured for the classical hydraulic jump. The results showed that the tailwater depth required to form a hydraulic jump and also the roller length of the hydraulic jump and the length of the hydraulic jump on a gradual expansion basin with the rough bed were appreciably smaller than that of the corresponding hydraulic jumps in a rectangular basin with smooth and rough bed. With the experimental data, empirical formulae were developed to express the hydraulic jump characteristics relating to roughness elements height and divergence ratio of wall. Also, the applicability of some empirical relationships for estimating the roller length was tested.

Erosion in river bends causes loss of agricultural lands, adjacent facilities, and fish habitat. W-weir structures are recommended for controlling and reducing soil erosion as well as developing habitat for fish and other aquatic organisms. This paper presents the results of an experimental study carried out to investigate the effect of a W-weir structure on a sinusoidal channel with a sinuosity of 1.12 on the scour volume and type. The W-weir was applied in three heights (0.5, 1, and 1.5) with $H_o/h$ ratio (the height of weir to flow depth ratio) and different hydraulic conditions (inflow Froude numbers 0.107, 0.142, and 0.178) tested for each structure. Bed topography was measured at the end of each experiment, and from that the types of scouring, maximum scour depth and length, as well as maximum ripple height and length were computed. Furthermore, by decreasing the height of W-weir from $H_o/h$ = 1.5 to $H_o/h$ = 0.5, the scour volume decreased from 24 to 78 percent on average for different inflow Froude numbers. The angle of inner arms of W-weir was chosen as 50°, 64°, 86°, and 124°. Minimum scour volume occurred in the angle of inner arms of w-weir 64° for different heights of W-weir tested. Finally, two scour morphologies were observed. This study provides insights to guide and design W-weir structures for river restoration projects.

Recent research has greatly focused on the environmental water supplement of rivers individually and independently. However, a comprehensive and integrated view of all rivers in the basin is simultaneously required in closed basins leading to lakes and wetlands. This has affected Lake Urmia, which is the second largest saltwater lake in the world. It has been in danger of drying up in recent years as a result of not allocating the required environmental flow (e-flow) due to the increase in water resource consumption in the agricultural sector and climate changes. In this study, a method derived from the flow duration curve shifting (FDCS) method is presented in addition to explaining the possibility of providing the e-flow of rivers leading to the lake. The method can make the least amount of change in the hydrological characteristics of rivers while providing the volume of required water by the ecosystem of lakes or downstream wetlands. Unlike the conventional method which presents the results on a monthly basis, the above-mentioned method is based on daily data of hydrometric stations and can calculate the amount of the environmental requirement of rivers in real-time according to the upstream inlet of the river. This method has been used in the Urmia Lake basin. According to the results, it can provide the environmental requirement of the lake by allocating 70.5% of the annual flow of rivers and thus can save the lake and the ecosystem of the region from the current critical conditions.

In the conducted researches recently the greatest focus has been on the environmental water supplement of rivers individually and independently. However, in closed basins leading to lakes and wetlands, a comprehensive and integrated view of all rivers in the basin is required simultaneously. This has affected Lake Urmia, which is the second largest saltwater lake in the world. This lake has been in danger of drying up in recent years as a result of not allocating the required environmental flow due to the increase in water resources consumption in the agricultural sector and climate change. In this study, a method derived from the flow duration curve (FDC) shifting method is presented in addition to the possibility of providing the environmental flow of rivers leading to the lake that can make the least amount of change in the hydrological characteristics of rivers to provide the volume of required water by the ecosystem of lakes or downstream wetlands. This method is based on daily data of hydrometric stations and, unlike the conventional method, which presents the results on a monthly basis, it can calculate the amount of environmental requirement of rivers in real-time according to the upstream inlet of the river. This method has been used in the Urmia Lake basin and according to the results, it can provide the environmental requirement of lake by allocating 70.5% of the annual flow of rivers and save the lake and the ecosystem of the region from the current critical conditions.