In the scope of the Program of surface water quality examinations in the Republic of Srpska (Bosnia and Herzegovina), hydrometric measurements and water quality examinations had been realized, where zooplankton and microzooperiphyton researches have been performed. Sampling were performed in the period from 6th to 20th May 2000, at 13 water courses with taken in total 21 samples. In qualitative structure of examined fauna, Rotatoria, Cladocera and Copepoda groups were treated, with ascertained in total 109 taxa from 41 genus. In qualitative structure periphyton taxa are predominant. On the basis of bioindicatory species structure it is noticed that dominant species are oligasaprobic and oligobetamesosaprobic character.

Creation of scientific basis for rational use of water resources is impossible without studying viability of the microorganisms, their influence on the formation of chemical properties of natural waters and an explanation of the principles of biochemical processes such as transformation of elements in the aquatic environment. The survey of microbial (bacterial) characteristics of watercourses in the Republic of Srpska was conducted on a total of 64 streams within Operational, International and National surveillance monitoring. Sampling and analysis of samples was performed during the period from May to October. The study included ecological and sanitary aspects of river quality.

In the scope of complex physical-chemical and biological water examination of Bocac water reservoir, the river Vrbas and trbutaries Ugar and Crna Rijeka, examination of standard microbiological indexes of water quality (aerobic organotrophs at 22-26 deg C and 37 deg C, total colliforms and colliforms of fecal origin) was performed during 2002 (March-November). Number of examined microbiological parameters was mainly in the scope of the 2nd water category (beta-mesosaprobic water) with worse water quality in upstream part of the reservoir. Ugar tributary had the best water quality, while Crna Rijeka had the worst status with obvious anthropogenic influence.

In scope of complex physical-chemical and biological examination of water quality of the Bocac lake, the river Vrbas and tributaries Ugar and Crna Rijeka, examinations of phytoplankton and zooplankton were performed during 2002 (March-November). In qualitative structure of phytoplankton 7 division were registered, with 93 taxa from 49 genera in total. In warmer period extreme domination have fire algae (Pyrrophyta). In zooplankton structure (Rotatoria, Cladocera, Copepoda) 78 taxa were registered from 36 genera, with distinct domination of Rotatoria group. According to saprobiological analysis species of olligo- and beta-mesosaprobic character are prevailing.

According to the plans, the town of Gacko tends to be water supplied from the water reservoir Vrba located at the river Vrba. About 150 to 200 m away is located ash basin. All ash basin area is oriented to the water reservoir and leaking water going directly to the water reservoir. The leaking water has high pH value, alkalinity, high content of sodium, potassium and sulphates. There are some heavy metals, but their concentrations are not significant. The influence of those contaminated water on the lake water quality is only little evident because of the high dilution rate.

Water quality monitoring of surface waters encompasses the watercourses of the river basins of Una, Vrbas, Bosna, Drina, Ukrina and the direct Sava basin. Apart from comprehensive analyses which demand determinations of physical - chemical characteristics, as well as the ihtiofauna composition, special emphasis is given to the analysis of the macrozoobenthos. 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 communities. Most of the aquatic habitats, especially flowing waters 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).

In the scope of complex water quality analysis of the Bocac reservoir, as well as rivers which flow into and out of the Bocac reservoir (Vrbas, Crna Rijeka) during the period from May to September 2008, the contents and the dynamics of the phyto and zooplankton were analyzed as biological parameters. The qualitative contents of the phytoplankton includes 5 divisions of total 27 taxa from 16 species; the tributaries contain 30 taxa from 19 genuses. The zooplankton (Rotatoria, Cladocera and Copepoda) contain 22 taxa from 16 genuses; the tributaries contain 32 taxa from 19 genuses with huge dominance of the Rotatoria species. By saprobiological analysis, species of oligo and beta mezosaprobiological character previal.

In the year 2010 ichthyological research on some Vrbas River tributeries located on wider area of Banjaluka city (Bosnia and Herzegovina) was carried out and the occurrence of 14 fish species was recorded. On the basis of the occurrence and abundance of fish species indicators as limnosaprobic parameter, water quality of the analyzed watercourses variated from oligosaprobic to beta mesosaprobic (I and II class of bonity) with saprobic index from 1.27 for Švrakava River to 1.81 for Vrbanja River. The obtained results indicate that water quality of this Vrbas River watershed was on satisfactory level for multiple purposes (in order to sustain ichthyofauna diversity and production and as potential protected areas and spawning zone for some endangered domestic fish species).

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.

During the period of 2004-2005 ichthyological research on natural waters of Bardaca wetland (Bosnia and Herzegovina) was carried out and the occurrence of 24 fish species was recorded. On the basis of the occurrence and abundance of fish species indicators as limnosaprobic parameter, water quality of the analyzed watercourses (rivers Matura and Brzaja) was found to be beta mesosaprobic (the 2nd class of bonity) with saprobic index 2.02 for Marura River and 2.03 for Brzaja River. The obtained results indicate that water quality of this part Bardaca wetland was on satisfactory level for multiple purposes (as a source of water for Bardaca fishpond and in order to sustain ichthyofauna diversity and production.