Seite - 645 - in Book of Full Papers - Symposium Hydro Engineering

transport occurs in the time period June to November with maximum mean monthly sediment load close to 23,000 m³/month. The sediment inflow at the Moragolla dam site will consist predominantly of silt material, with an important sand content, which will increase with rising river flow. By small discharges i.e.: close to 10 m³/s as observed during the dry season, the sand content will be close to 10-15%. As the discharge increases the sand content can reach up to 30% of the total sediment inflow. 3. RESERVOIR SEDIMENTATION AND COUNTERMEASURES 3.1. METHODOLOGY The time path of the reservoir storage development has been initially assessed for the no-action scenario with purpose of the determination of the reservoir service lifetime if no sedimentation management measures are implemented. The assessment was performed with one-dimensional simulation with the widely used numerical model HEC-RAS v. 5.03. The results of the numerical model served in addition for the calibration of the REServoir Conservation - 2 (RESCON- 2) model that was used subsequently for the screening and evaluation of the state-of-the-art sediment management techniques. The RESCON approach was developed and published in 2003 by the World Bank [4] with the purpose to provide a tool that will allow the identification of the technically viable and economically optimal approach for sustainable management of water storage reservoirs. The RESCON approach was recently upgraded by Fichtner for the World Bank Group and the beta version of the RESCON-2 software is now freely available to download at the internet portal of the International Hydropower Association (IHA)*. The improvements incorporated in RESCON-2 can be categorized as follows (5):  Improved procedure for calculation of the reservoir storage development, allowing allocation of sediment deposits between active and inactive storage as well as partitioning between bedload and suspended load  Extension of palette of assessed sediment management techniques  Incorporation of intergenerational equity issues in performed economic appraisal through the concept of declining discount rate  Climate change analysis allowing the assessment of sediment management as adaptation strategy for increasing the resilience of the infrastructure  Graphical User Interface (GUI) enhancing the user-friendliness during model setup and result reading It is pointed out that RESCON-2 serves for a rapid screening and it is not intended to replace detailed studies. The RESCON-2 program is based on * available at https://www.hydropower.org/sediment-management/ 645