Sediment balance of the lowland tropical reservoir of Timah Tasoh, Perlis, Malaysia

A study was carried of out to assess the sediment balance of a shallow Timah Tasoh Reservoir (Area: 191 km²). Streamflow gauging and water sampling was carried out at three river inputs to the reservoir, and at the reservoir outlets. River water samplings were carried out every two weeks but frequent and intensive sampling during storm events. The land use in the catchment area ranging from urban area to agriculture, sugar cane, rubber, paddy, rural villages, small towns, quarrying and mining activities. Suspended sediment load data was used to derive the sediment balance. Jarum River (S1), Upper Pelarit River (S2) and Chuchuh River (S3) produced 10,032.3 t; 6,439.2 t; 1,061.4 t of sediment respectively while suspended sediment yield in S1, S2 and S3 were 155.8 tkm^-2yr^-1, 150.7 tkm^-2yr^-1, and 71.7 tkm^-2yr^-1 respectively. Storms play a major role in transporting sediment from the catchment areas. Almost 88.7% of the total suspended sediment yield is transported from S1, 56.7% from S2 and 80.1% from S3. The annual sediment output load at the reservoir outlet was 1 653.0 t. From the total of 17 532.9 t of suspended sediment input to the reservoir, 15 879.9 t was stored in the reservoir. The estimated trapping efficiency of the reservoir is 90.6%. Designing sediment control and management strategies as well as increasing storage elsewhere in the watershed will help reduce the efficiency of sediment delivery from the individual catchment to the river. Alternatively, reductions could also be achieved by reducing sediment output through the construction of wetlands and the use of buffer strips.