Monitoring of the Iron Gate Hydropower and Navigation System on the Danube River - page 6

Presently, suspended sediment transport is permanently monitored at ten monitoring profiles within the IG1 reservoir: four at the entry of the Danube and its tributaries (the Sava, Tisza and Velika Morava), five within the reservoir range, and one at the dam site. Also, there are two monitoring cross-sections within the IG2 reservoir and one at the dam site (Fig. 12).


Fig. 12: Profiles for suspended sediment monitoring


Collection of water and sediment samples is done at all monitoring profiles, on a daily basis, in order to determine the "surface" suspended sediment concentration. Water samples (Danube 10 L, tributaries 5 L) are collected at selected permanent points on the surface of the monitoring cross-sections and transported to a sediment laboratory, where concentration and grain-size of suspended sediment is determined. Complete field measurements of water and sediment parameters are performed periodically (1-3 times a year), to identify the water flow and sediment characteristics at various points, verticals, and across the monitoring profile (Fig. 13). Morphological changes within the Iron Gate reservoirs are monitored via periodic survey of permanent cross-sections.

This activity, complementary to the monitoring of sedimentation within the reservoir via the sediment balance, is also important because it provides inputs for hydraulic backwater analyses and information for fairway management. The initial condition of the Iron Gate 1 reservoir was determined by the survey of 108 cross-sections in 1970. Till 1976, the survey and relevant calculations were performed every year for the same cross-sections. Afterwards it was found that the number of cross-sections is not sufficient. Consequently, the number was increased to 315 (256 on the Danube River), while the period between surveys was set on 3-5 years. The reservoir part downstream of km 1075 (the so called "immediate reservoir", where the most significant morphological changes were expected), is furnished with a dense net of cross-sections. Afterwards, the surveys were performed in 1981, 1984, 1988, 1997, 2005 and 2010.


Fig. 13: Results of a complete measurement of flow and suspended sediment transport