Investigation of river flow alterations using environmental flow assessment and hydrologic indices: Tajan River Watershed, Iran

• Published in: International journal of river basin management Vol. 11; no. 3; pp. 311 - 321
• Main Authors: Ghanbarpour, M. Reza, Zolfaghari, Somayeh, Geiss, Christoph, Darvari, Zahra
• Format: Journal Article
• Language: English
• Published: Abingdon IAHR 01-09-2013; Taylor & Francis; Taylor & Francis Ltd
• Subjects: Alterations; Assessments; base flow; Dam construction; Dams; Earth sciences; Earth, ocean, space; Environmental flow; Exact sciences and technology; Freshwater; hydrograph; hydrologic alteration; Hydrology; Hydrology. Hydrogeology; Iran; reservoir operation; River flow; Rivers; Tajan Watershed; Thresholds; water management; Water resources; watershed hydrology; Watersheds; Middle East; Iran; Asia; base flow; reversals; rivers; hydrology; Environmental flow; reservoirs; monthly average; drainage divide; dams; surface water; reservoir operation; drainage basins; Tajan Watershed; hydraulics; Iran; hydrologic alteration; water resource management; alteration; construction; annual average; hydrographs; methodology
• ISSN: 1814-2060; 1571-5124; 1814-2060
• DOI: 10.1080/15715124.2013.823978

In this research, environmental flow assessment (EFA) and hydrologic indices have been applied to analyse flow alteration due to the construction of the Soleyman Tangeh dam on the Tajan River Watershed in northern Iran. Some different hydrologic indices, base flow index (BFI), river flow pattern, and minimum and maximum river flow thresholds have been used to assess hydrologic alteration in the watershed, based on available flow data during pre-dam and post-dam years. In addition, three EFA methods namely, Tennant, flow duration curve, and environmental flow requirements, have been used to recommend the minimum flow requirements for post-dam years. The main objective of this research is to determine the environmental flow thresholds and to quantify on how dam construction altered the hydrology of the watershed. The results have shown that average annual and monthly flow, minimum daily flow, and BFI significantly decreased in post-dam years. Moreover, alteration patterns of river flow and hydrograph reversals were detected. This research is a preliminary analysis to provide insights on embedding environmental flow to integrated water resources management in the similar watersheds with lack of accurate and sufficient ecological and river hydraulic data.