Water Quality Evolution in Gozna and Secu Reservoirs, Semenic Mountains, Romania

Abstract

Knowing and tracking the evolution of water quality in reservoirs is very important, especially if one of the functions of the reservoir is to provide the water supply to the localities. The chemical, thermal and physical changes which the flowing water undergoes when it is stilled through hydrotechnical structures, like dams, can seriously contaminate water from the reservoir and the river downstream. The grade of deterioration in the water quality is in general related to the retention time of the reservoir, its storage capacity in relation to the amount of water flowing into it. The parameters of water quality determine the treatment technology and implicit, influence the cost of drinking water. Gozna and Secu reservoirs are located in the Semenic Mountains, were built as multi-purpose systems for water management. Their purpose was to produce hydropower, to supply drinking water to Resita city, mitigate flood waves and to be used as recreational areas. In this paper, the evolution of water quality on both reservoirs is analyzed based on the water samples collected over 11 years’ time period (2001 - 2011). The main water quality parameters from these reservoirs are: water transparency, temperature, pH, dissolved oxygen, CBO5, CCOMn/O2, total nitrogen, total phosphorous, density, suspensions. On the base of the obtained results from the water quality evolution process analysis, the specialists in the domain can anticipate the problems, causes of water quality degradation and can establish the adequate measures for water quality conservation and improvement. Today, worldwide, is an increasing interest in the reservoir water quality since the water resources are not expanding as fast as the water demands. Because the fresh water becomes more limited (due to pollution, climate change etc.), the quality of the water becomes increasingly important.