Extract from the paper by Marina Babic-Mladenovic submitted to the International Conference on Planning and Management of Water Resources Systems, 25 - 26 September 2008, Novi Sad, Serbia (e-mail: Marina.Babic-Mladenovic@jcerni.co.yu)

Along almost of its entire length of 580 km, the Serbian sector of the Danube River is a typical alluvial watercourse, transporting significant amounts of suspended sediment. This sector is marked by very large alluvial tributaries (Drava, Tisa, Sava and Velika Morava) that effect the sediment regime of the Danube. The construction of the Iron Gate Dam (943 km upstream from the Black Sea), created a large reservoir on the Danube, and inducing sediment deposition. As well known, the sediment regime depends upon the hydrologic and hydraulic conditions of the river and upon the power plant’s operating mode. In order to highlight relevant phenomena and processes occurring upstream and within the Iron Gate Reservoir, the author used comprehensive results of high-quality field investigations, conducted before and after the construction of the dam in 1972. Altogether 178 measurements were made before the construction of the Dam (1962-1967), and 84 measurements after the construction of the Dam (1974-2000).

The paper describes the quantitative analysis of the sediment transport process, based on statistical methods making use of data obtained by measurements of water and sediment transport. Applying a multi-parameter regression analysis, new formulas were defined for the estimation sediment transport in natural and backwater regimes. Two specific formulas were developed: the first for the natural sediment regime and the second for the estimation of sediment transport in the backwater. Although the empirical relations were based on suspended sediment measurement data only, they can also be used to estimate the total sediment loads within the Danube, with an adequate degree of accuracy. The established empirical functions are very significant in both scientific and practical terms.

Problems related to sedimentation of the Iron Gate reservoir are discussed in the second part of the paper. Reservoir sedimentation was in the planning phase considered as a very slow time-evolving process and thus left to be deal with it in the future. Nowadays, after 30 years of reservoir operation, an immediate action has become necessary, having in mind the possible environmental, social and economic consequences of sedimentation. Therefore, stakeholders and decision makers should be interested in long-term prediction of changes as regards to both sediment quality and quantity. (by Stevan Bruk)