## 1 Introduction  
Worldwide, domestic sewage, untreated industrial effluents, and agricultural fertiliser leaching can contaminate river systems [1, 2, 3]. Numerous contaminants, including metals and nutrients, are linked to these activities and pose a serious environmental risk to freshwater resources worldwide [4, 5, 6, 7, 8, 9, 10, 11]. In urban areas, stream sediments are particularly vulnerable to metal pollution due to the high density of anthropogenic activities such as industrial discharge, domestic wastewater, and urban runoff. In Turkey, uncontrolled discharge of industrial, agricultural, and domestic waste into water bodies has become a major source of metal contamination, particularly in urban stream systems, leading to the degradation of water quality and ecological health [12, 13, 14, 15]. Once introduced into the aquatic environment, metals can bioaccumulate and enter the food web, ultimately threatening human health through biomagnification [12, 13, 16]. Metal concentrations in river sediments are influenced by a combination of both anthropogenic and natural factors. These include the cumulative effects of pollution sources, geological formations, and regional climatic conditions. The nature of these pollution sources--point-based or diffuse--and their spatial distribution and surrounding land use patterns significantly affect contamination levels [13; 17; 18; 19]. In particular, sediment characteristics such as texture, organic carbon content, and pH can greatly influence the accumulation and mobility of metals. Land use also plays a critical role in determining the extent of water and sediment pollution [15; 19; 20]. Assessment of metal pollution often employs widely accepted contamination indices such as Contamination Factor (CF), Enrichment Factor (EF), Geo-accumulation Index (Igeo), and Pollution Load Index (PLI), which are reliable tools for determining sediment contamination levels and potential ecological risks. The Keban Dam Lake catchment is an important water resource affected by urbanization, agriculture, and industrial activities. Limited previous studies have identified heavy metal accumulation in some stream sediments in the region, potentially posing ecological risks. Key pollution sources include urban wastewater discharges, agricultural runoff, and nearby industrial facilities. Therefore, monitoring sediment quality and metal contamination in the Keban Dam Lake catchment is critical for effective environmental management. To provide context for the assessment of metal contamination in stream sediments draining into Keban Dam Lake, similar studies conducted in various Turkish river basins are briefly reviewed. These studies employed commonly used contamination indices to evaluate pollution levels and identify anthropogenic and geogenic sources. In a study conducted on the Seyhan River (Turkey), heavy metal contamination was assessed through a combination of indices, including the Contamination Factor (CF), Enrichment Factor (EF), Geo-accumulation Index (Igeo), and Sediment Quality Guidelines (SQGs). The findings indicated that Cr and Ni were present at contamination levels classified as \"moderate to very strong,\" while Cu, Pb, and Zn were categorised within the range of \"unpolluted to moderately polluted\" [21]. Similarly, in another study on the Tigris River in southeastern Turkey, a combination of CF, Pollution Load Index (PLI), Igeo, and EF was applied to assess sediment contamination. The results demonstrated that Cu, Cobalt (Co), and Zn exhibited significantly high CF values, suggesting notable anthropogenic contributions. These elevated levels were primarily attributed to waste discharges from nearby copper mining activities [22]. In their study, [PERSON] and [PERSON] [23] assessed metal contamination in sediments of the Euphrates River tributaries using pollution indices (CF, Igeo, PLI) and statistical methods, identifying Cr, Cu, and Zn as key pollutants linked to anthropogenic sources.