A GIS Based Study to Investigate of the Ecological Impacts of Successive Dams on Surface Water Quality: A Review of the Sakarya Basin, Türkiye

The present study aimed to assess the status of successive dams on surface water quality, especially in reducing organic pollution levels, and their effects on the ecological life were investigated. Water samples were collected seasonally from three dam’s monitoring stations. Temperature, pH, dissolved oxygen, electrical conductivity, turbidity, ammonium nitrogen, nitrite nitrogen, nitrate-nitrogen, sulfate, total phosphorus, chemical oxygen demand, biochemical oxygen demand and total hardness parameters were measured in surface waters. The Geographic Information System (GIS) was used to produce thematic maps of the investigated parameters. Stations used as point feature layers were mapped using quantitative labeling via symbology. The results were compared with Turkish Regulation, 2015 and EC Directive on the quality of fresh waters needing protection or improvement to support fish life (2006) guidelines. According to the results of the analysis, Dams that are located one after the other contribute to the partial cleaning of the water by resting. Sarıyar, Gökçekaya, and Yenice Dams were built on the Sakarya River, which is one of Türkiye’s biggest and most significant river systems, for electric supply and utility of water for irrigation and fishery activities. Gökçekaya Dam Lake was built between Sarıyar Dam and Yenice Dam, which are situated in the same line of Sakarya River. Gökçekaya and Yenice Dams are fed by Sarıyar Dam Lake and do not receive fresh water. The fact that the three dams are established one after the other aids in the water’s resting and the aids in removing the suspended solids/suspended load. But, this research show that domestic, industrial, agricultural wastes carried by the branches of the rivers caused algal blooms in Dam lakes, especially which are not fed with fresh water. Due to organic pollution the decrease in dissolved oxygen, especially from time to time, negatively affects the ecological life in the lakes.