Regressions on Monthly Stream Discharge to Predict Sediment Inflow to a Reservoir in Algeria

Abstract

An understanding of the quantity of sediment deposited in a reservoir is necessary for effective reservoir and basin management. Sedimentation affects the useful life of a reservoir as flood control and water supply. The present study has been carried out to assess sediment load in the wadi Bouhamdane in northeast Algeria to be able to estimate sedimentation in a reservoir located upstream of the gauging station. Measurement data of suspended sediment and water discharge were available during 13-year period (1975/76-1987/88) in the Medjez Amar gauging station. The data were provided by the National Agency of Hydraulic Resources, which carried out the sampling and initial calculations of concentration. Several data sets, derived from daily mean water discharges and daily mean suspended sediment discharges were used to develop sediment rating curves for small periods of time when water sampling was insufficient. Relationships between monthly mean water discharge and monthly sediment load were used according to single and seasonal ratings. Additionally, a technique was devised to correct for log-transform bias on the sediment rating curves. Once the water discharge-sediment rating curves were defined, they were used with water discharge data to predict monthly and annual sediment inflow to the reservoir. The sediment rating estimates were judged adequate to predict the Bouhamdane reservoir fill. The total suspended sediment load carried by the wadi Bouhamdane from 1975/76 to 1987/88 was calculated to 3.90 x 10 6 tonnes and the mean annual sediment yield was 271 T km-2 yr-1. During the reservoir period 1988/89 to 2006/2007 the water discharge-sediment rating curves gave 5.38 x 10 6 tonnes. In terms of sediment entrapment in the reservoir by damming, the sedimentation in the reservoir during the 19-year period was predicted to be 6.29x10 6 m 3. This study has estimated a loss of storage in the reservoir due to sedimentation of 0.17% yr-1 .