Enhancing Hydraulic Efficiency of Side Intakes Using Spur Dikes: A Case Study of Hemmat Water Intake, Iran.

This study investigates the problem of low efficiency and the lack of a water supply at the Hemmat Water Intake, in Iran, where severe sediment accumulation was observed at the intake mouth. The Flow-3D software was used to simulate the flow patterns under various scenarios of hydraulic regimentation works. The considered parameters include: (i) three alternative locations of the spur dike (i.e., a spur dike placed on the opposite side of the intake inlet and aligned with the upstream edge of the intake, to be regarded as a witness spur dike; a spur dike at a distance D_S of 7 m downstream of the witness spur dike, which implies a dimensionless distance D_S/b_i1 of 1/3, with b_i1 being the intake opening width; and a spur dike at a distance of 7 m upstream of the witness spur dike with a dimensionless distance, still, of 1/3); (ii) four spur dike lengths, L_S/B_r, with L_S being the effective spur dike length and B_r the approach river width; and (iii) five spur dike deviation angles of 75, 90, 105, 120, and 135 degrees (the deviation angle is the angle between the spur dike axis and the original river-bank line from which the spur dike extends). The results showed that, with the increase in the relative spur dike length (L_S/B_r), the velocity of the flow entering the water intake increases by 11%. A spur deviation angle of 135 degrees increases the flow depth at the intake inlet by 9% compared to a smaller deviation angle of 75 degrees. In addition, the spur dike increases the flow shear stresses at the intake inlet by up to 50%. Overall, the main flow of the river with the highest velocity and depth, and best directed towards the water intake, occurs for the placement of the longest spur dike (i.e., L_S/B_r = 0.46) in front of the inlet (i.e., witness spur dike) and for a spur dike deviation angle of 135 degrees. The spur dike increases the shear stress at the intake entrance by more than five times with respect to the case of its absence. In general, the presence of a spur dike on the opposite bank and with a deviation angle in the direction of the intake inlet well directs the main flow towards the canal intake. Moreover, it reduces the possibility of sedimentation in the canal inlet by increasing the flow velocity. Therefore, the results of this study could also be useful in increasing the hydraulic efficiency of lateral intakes by reducing the sedimentation phenomena. [ABSTRACT FROM AUTHOR]