Evaluation of Sediment Transport in Ephemeral Streams: A Case Study in the Southwestern Saudi Arabia

Sediment transport is essential for the estimation of the life of dam reservoirs. Arid regions lack sediment transport studies due to the lack of measurements for either water or sediment, and therefore, the life of dam reservoirs cannot be estimated accurately. We developed a power law sediment rating curves from measurements from 7 gaging stations of some subbasins in southwestern Saudi Arabia. These curves are developed for each subbasin and a generalized equation of the two basins are also developed. The regression parameter “a” ranges from 0.0008 to 0.0088, and the power “b” ranges from 1.3753 to 1.7223. Validation and cross-validation were performed on two Wadis namely: Wadi Yiba and Liyyah basins. The developed equations were used to estimate the sediment yield of the study area. The results show that the regression parameters of the sediment rating curves vary from one subbasin to the other and that the sediment per unit area ranges from 88 to 374 Ton/km²/year for Wadi Yiba, and from 297 to 1324 Ton/km²/year for Wadi Liyyah. The cross-validation of the equations developed for the two Wadis showed R² = 0.99. The t test supported the null hypothesis of having no significant difference and therefore indicated the possibility of applying Yiba/Liyyah rating curve to other regions in Saudi Arabia. Hydrologists and/or engineers are advised to utilize the developed equations to estimate the lifespan of a dam reservoir, by acquiring the dam design data, gathering current rainfall data, conducting rainfall-runoff modeling to account for the old data, and then applying the derived equation.