The role of sediment rating curve development methodology on river load modeling

The study aims to evaluate the performance of four sediment rating curve development methods, namely (i) simple rating curve, (ii) different ratings for the dry and wet season of the year, (iii) different ratings for the rising and falling limb of the runoff hydrograph, and (iv) broken line interpolation that uses different exponents for two discharge classes at the outlet of the Venetikos River catchment, located at Western Macedonia, Northern Greece. The goal is to provide guidance on the selection of the most appropriate one for the estimation of sediment discharge (yield) at this gauging site (basin), as well as to properly assess such values. The necessary field measurements (discharge, sediment discharge, discharge-sediment discharge pairs) were conducted by the Greek Public Power Corporation. The performance of each method was evaluated by executing a statistical analysis (1965-1982), using as benchmark the observed mean monthly sediment discharge values. The broken line interpolation method performed best, not only by meeting the desired criteria of most statistical indicators used but also by being overall superior to all other methods. Thus, henceforward is to be treated as the representative rating curve development method for the specific site. Finally, an attempt was made to evaluate the estimated (and observed) sediment yield values against the ones attributed by four empirical equations, yet with relatively poor results.