Struma River-Water, Environment, Biodiversity, and Agriculture

General aim of the study is to be presented summarized data, result of 15 years investigations of the valley of Struma River, which springs from the Vitosha Mountain near the capital city of Sofia, Bulgaria and flows into Mediterranean Sea in Greece near the city of Thessaloniki. The study has begun during 2007–year of the acceptance of Bulgaria in EU and it has continued by now during 2023. Bulgaria, Serbia, North Macedonia, and Greece) are the illegal landfills, dumping of waste and household waste water canals, result of the living process of the local population without respect to any National and EU legislation. Equal to this harm is the poor work of municipal and governmental authorities towards waste management of the area. Second source of contamination is farming and construction activities. Usage of fertilizers is widespread in the area during spring and summer period. Farming and construction waste dumped illegally in river beds also contaminates the water and soils in the area. The region is not industrially developed and industry is not the main pollutant of the area. It is established that population of the fish species closely relates to contamination of the water. Contaminated rivers do not have any fish species. Feeding streams bring contamination into Struma River and decrease population of some fish species such as brown trout fish (Salmo trutta fario). This specie disappears in water, contaminated with cyanuric acid (Novoselska and Bistritsa Rivers) or in water contaminated with thermal mineral water (Banshtitsa River).