Investigating effects of sequentially built run-of-river type hydroelectric plants (HEP) on the values of water quantity, water quality and suspended sediments of Kabaca Creek

The forested watersheds, also known as hydrological units, continuously feed surface water and groundwater resources by draining rainfall they receive. However, in recent years, the natural watersheds have also been affected in a serious way from the negative impacts caused by a large number of human activities (mining, run-of-river type hydroelectric plants (ROR-HEP), road construction, urbanization etc.) permitted mainly in the upper part of Turkey's forested area. One of the regions where some of the interventions listed above have been intensively taking place is the upper forested parts of the Murgul Stream Watershed of Artvin. Even tough three ROR-HEP are currently running along Kabaca Creek, a tributary found in this region, a limited number of scientific studies have been conducted on the possible effects of these structures on the creek system. From this point of view, establishing what type of changes the ROR-HEPs on the Kabaca Creek may cause on the amount of water, some water quality parameters and the amount of suspended solids (TSS) was determined as the main objective of this study. Fort this purpose, while the monthly discharge and TSS quantities were estimated at ten sampling points along the Kabaca Creek, the measurements of some water quality parameters (pH, water temperature, dissolved oxygen, conductivity, salinity, total dissolved substances, ammonium and nitrate-nitrogen) were done by using the portable YSI (Professional Plus) device. The results revealed that, in general, the quality of water in the creek was clean -except for some sampling points and sampling times. However, it was determined that the quantities of electrical conductivity 62 µs/cm, salinity 0.04 ppt and total dissolved substances 61 mg/l measured in the locations of the creek before its water being taken into the transmission pipes were significantly increased to 87 µs/cm, 0.06 ppt ve 89 mg/l, respectively, in the points of the creek where "compensation flow" released by the ROR-HEP. It was thought that this outcome was associated with the substantial drop in water amount of the creek due to the ROR-HEP's use of 90% of water and the reduction of mean discharge of 2.53 m3/s before the regulator to 0.93 m3/s after the regulator supported this.