Evaluating sediment yield at King Talal Reservoir from landslides along Irbid–Amman Highway

With a capacity of 86 MCM, King Talal Reservoir is considered a major water supply in Jordan. It was built exclusively to irrigate the land in the Jordan Valley. Unexpectedly, the design capacity of the reservoir was confronted by the elevated sediment inflows during and after the construction of the Irbid–Amman Highway in 1987. Since then the annual sediment inflow measured at the mouth of the reservoir was higher than expected in a similar year. Notably, the over-wet season of 1991/2, as a result of six major landslides along the highway, registered the highest sediment inflow into the reservoir. In the present work the fractional contribution of these landslides to total sediment yield at the reservoir was evaluated. The evaluation was made by applying the well-known erosion model, AGNPS (Young et al., USDA Conservation Research Report 35, 1987). To calibrate the model, it was successively applied from 1980/1 to 1990/1 on the measured sediment data before the occurrence of landslides. With a slight tune-up of some of the King Talal watershed erosion variables, fairly good agreement was obtained in some years. However, the disagreement noticed in other years might be attributed to some conservation measures practised in the watershed. Because the serious landslides occurred in the wet season of 1991/2, the model was run for the two scenarios in this year: with and without landslides. The difference in results represents the contribution of landslides to sediment yield at the reservoir. It is concluded, based on these results, that landslides, if continued without control, will definitely jeopardize the design capacity of the reservoir.     

Erosion risk assessment and sediment yield production of the King Talal Watershed, Jordan

 King Talal Dam (KTD) watershed is the most important one in Jordan. At its outlet lies the KTD (80 MCM capacity) which serves irrigation purposes in the Jordan Valley. However, the dam suffers from accelerated annual sedimentation. Therefore, this study is directed to assess the erosion risk over the watershed, and to simulate actual annual sediment yield at the dam in order to devise the appropriate conservation practices. Generalized assessment was first conducted over the watershed on the basis of drainage texture, rainfall erosion index (R), and the ratio p²/P. As a result, the watershed is divided into zones of severe, high (gullying), high (overland flow) and low erosion risk. Sediment yield at the dam was evaluated by a simulation model. For model validation the simulation results were compared to the measured values over 12 years period, and a good agreement was obtained in some of the years. The simulation results allow us to assess the application of two practical conservation practices: terracing and plantation of trees. Received: 18 November 1997 · Accepted: 18 May 1998     

Evaluation and rehabilitation of dam seepage problems. A case study: Kafrein dam

The intention of this study is to locate the probable sources of the Kafrein dam seepage problem. A methodology known as excitation-response analysis will be considered. Analytical expressions, depicting the groundwater level response in the underlying aquifer as a result of changes in the reservoir water level, were derived from a linearized groundwater flow equation for one-dimensional semi-infinite, isotropic and homogeneous porous media. The results revealed that a large proportion of the seepage water originates from a site at a distance about 1 km from the observation point M1 and streamlines along the existing faults. Emphasis in this work was also placed on controling and mitigating the seepage problem.