Settlement performance evaluation of longitudinal settling basins - A case study on Golfaraj and Iry-Siah Rud pump stations, Iran

Abstract

One of the most important elements of river intake is settling basins for water sediment removal. Settling basins play an important role in supplying appropriate water for irrigation networks and power plants. Therefore, it is necessary to design them carefully based on the local conditions. Our objectives were to determine the properties of sediments entering into the intake systems of two pump stations (Golfaraj and Iry-Siah Rud) by sampling the water suspended load in different points of the systems and to investigate the performance of settling basins in Iran. The suspended load samples were taken from sections before and after the settling basins at three depths of 0.2 y, 0.6 y, and 0.8 y (y is the depth of the cross section from the water surface). Evaluating the characteristics of sediments entering into the stations showed that the mean diameter of the sediment particles is 0.0035 mm and 0.002 mm at the transmission canal and suction basins, respectively. Approximately 90% of the sediments entering into the stations have a diameter smaller than 0.03 mm. In high sediment conditions, statistical analyses revealed that there is a significant difference (p<0.05) between the mean cross sectional suspended concentrations, before and after the settling basins. The results indicated that the Golfaraj settling basin, by removing 22.75% of sediments did not have proper performance, as well as the Iry-Siah Rud station. Based on the condition of the stations, we recommend the use of the additional structures such as guide walls with sluiceway, doubled sills, and pre-settling basins and proper designing operation to reduce the problems related to sediment particles.