Determination of river flow and sediment regime changes in response to construction of regulating dams: an indicator-based approach

Construction of dams causes changes in the natural flow and sediment patterns of rivers, disrupting their ecosystems. This study aims to evaluate how two dams in Ardabil province affect river flow and sediment load indicators. Several indices, including mean annual flow/sediment load (A), flow/sediment load duration curve difference (M), flow/sediment load duration variability (Dv), and seasonal period (SP), were employed to evaluate the impact of regulatory dams on the monthly flow/sediment regime of the river. Results indicate similar monthly flow and sediment load values at the upstream and downstream stations of Yamchi dam, with a slight increase at the downstream station of Sabalan dam. Yamchi dam had a more substantial impact than Sabalan dam on flow and sediment load indices. Both dams exhibited high seasonal amplitude (SA), signifying significant flow and sediment load variability. The Yamchi dam had more effect on flow index changes, with a flow duration curve difference (M = 0.77). Additionally, the changes in sediment-related indices were greater at Polealmas compared to Doost Bigloo (0.98 vs. 0.8), indicating a reduced sediment-related impact during the study period. The monthly changes in flow and sediment load at the upstream and downstream stations of both dams followed the same pattern. The study emphasizes the different impacts of dams on the flow/sediment load regime of the river, implying varying ecological implications on the river ecosystem and riparian zones. The findings emphasize the importance of considering multiple indicators to comprehensively evaluate dam impacts on river dynamics and underscore the impacts on flow regime and river ecosystem.