Abstract:
During last three decades, Algeria is known for an immense and ambitious program in building of dams. Climatically, East Algeria is of the most abundant rainfall in the territory, where 25 dams are recently in operation, distributed through watersheds, with very contrasting physical characters. On the hydrotechnical plan, it’s characterized by the large variety in hydraulic properties specified from the perspective of their basins catchment, availability of lakes/reservoirs, and other auxiliary works. Data of water balance from the National Agency of Dams and Transfers (A.N.B.T) associates the follow-up and studies on the monthly and annual evolutions of entries, exits and deficits in the dams, as well as the knowledge of the hydrological behavior of the construction driven by the rainfall and other climatic fluctuations generally. Based on the analysis in ten dams with a hydrological observation over 23 years (from September 1990 to August 2013), a significant difference between the average interannual regulated volume (21.0 hm³) and theoretical regulated volume (37.7 hm³) shows an importance deficit in the water supply system which is strongly related to the frequency of wet and dry years. A chronological graphic method, with a statistical approach in data processing (type ""Bertin matrix""), is applied for three principal parameters (input, rainfall and storage rate). The result indicates a strong relationship between the parameters studied: a clear growth from the dry years from September 1990 until August 2002, and vice versa for wet years from 2003. These results are confirmed by the wavelet analysis: the dams storability are strongly influenced (from 66 % to 93 %) by a climatic variability and the left (from 7 to 34 %) is related to other factors such as the physiography of basin catchments. Results of the water balance show strong water losses by evaporation. The volume of water leaked, particularly on the karst sites (Foum El Gherza and Hammam Grouz), can reach to a significant peak specifically during the wet years 1990/91 and 2004/05. Otherwise, the phenomena of risings origins from excessive volumes evacuated from reservoirs or drainage of dams as details in the flood study for three dams Cheffia, Zardezas and Foum El Gherza. The quantification of sediment volumes in the dams (bathymetric campaigns 2004 and 2014) shows a reduction in storage capacity of the dams over time with a storage loss of 231 hm³ according to the survey in 2004, and 328 hm³ comparing to 2014. Finally, the analysis focuses on the inter-basin water transfer systems from large dams, and on the possibility of an interconnected management system to cooperate the basins in Eastern Algeria.
