A Comparative Study for Provision of Environmental Flows in the Tapi River

Abstract

Environmental flows are defined as the flow required into a stream to maintain the river’s ecosystem. The notion of Environmental Flow Allocation (EFA) ensures that a sufficient amount of water is delivered to the stream to maintain ecological integrity. The objective of this study is to examine environmental flows and determine the best acceptable strategy for providing flows into the river in the Lower Tapi Basin. To achieve this objective, daily discharge data from three sites, Ukai (period 1975–2020), Motinaroli (period 1990–2021), and Ghala (period 1995–2005) were collected and analyzed using the Tennant, Tessman, variable monthly flow (VMF), and Smakhtin methodologies. A comparative analysis was carried out on all three sites using the four methodologies. The Tessman and VMF approaches have a strong connection with the computed environmental flow requirements (EFR), according to the results. The calculated EFR was found to be in the range of 30–35% of mean annual flows (MAF). The maximum EFR found at station Ghala is about 54.5% of MAF according to the Tessman method. Such research will help to prevent future degradation of the river by supplying flow in accordance with the EFR, and it will also be used by stakeholders and policymakers to allocate water to preserve the ecosystem.

Keywords

• environmental flow requirements (EFR)
• Tessman
• variable monthly flow (VMF)
• Tennant
• Smakhtin method
• calculated environmental flow requirements