The paper shows available water resources potential of karsts spring waters of Carpatho-Balkan region of east Serbia. Basic elements of water balance are also given, as well as quantitative indicators of low flows. Karsts spring yield is compared to the domicile waters of Serbia. We can also read certain comments and see an estimation maximum usage of these karsts waters.

Water quality analysis of Zelengora natural lakes, were included researches of Kotlanicko, Orlovacko and Lake Donje Bare. Apart from comprehensive analyses which demand determinations of physical-chemical characteristics, special emphasis is given to the analysis of the makrozoobenthos. As a part of all water ecosystems, benthic invertebrate serve as a reliable indicator of the quality and changes of the environment, due to a series of advantages in relation to other aquatic communities. Most of the aquatic environments of good quality of water and benthic state, enable various of benthic invertebrates communities with moderate formation of species within the overall number of the present individual species. This kind of communities react to possible changes in the community composition (abundance and macroinvertebrata composition).

Researches of the Zelengora natural lakes during 2008 were performed in Orlovacko, Kotlanicko and the Lake Donje Bare. Water quality analysis of natural lakes of Zelengora were based on preliminary examination of basic physical and chemical parameters, as well as microbiological parameters. In the scope of biological examinations, phytoplankton, zooplankton and benthic fauna were determined. Due to the lack of data on biodiversity of examined natural lakes and whole area of National park Sutjeska results obtained in this research could only represent the first step toward further examinations, as well as the nature and biodiversity preservation in the Republic of Srpska.