Abstract:
A river's natural prominence is verified by the environmental flow criterion. Rivers of
Bangladesh experience precise high flow during the monsoon and low flow during the dry
period due to their terrestrial placement. This study project aims to evaluate the Jamuna
River's e-flow. The first goal of this study is to choose the most effective methodology
among the accepted e-flow measurement techniques for the Jamuna River. The second goal
is to evaluate the e-flow for fisheries, maintaining the river ecology and morphological
balance. Environmental flows are not only evaluated from hydrologic and hydraulic
perspectives but also incorporating habitat quality along with holistic approaches.
Daily discharge statistics from selected stations of BWDB have been gathered and
examined. According to the Tennant method, the Jamuna River must flow at least 6287
m3/s from December to March and 42580 m3/s from July to September to be sustainably
managed. The FDC Method indicates that the 90th percentile flow is 6480 m3
/s in the dry season and 17008 m3 /s in the rainy season. The Wetted Perimeter method estimates that
6531 m3/s e-flow should stay in the river all year round to ensure aquatic accommodation
for marine species. The Habitat Simulation analysis shows that the flow rate required for
Golda fish is 3893 m3/s from November to May and 5099 m3 /s from June to October. From July through October, Hilsa fish requires 25228 m3
/s of water. Carp fish requires a minimum of 992 m3/s in December through February and a maximum of 25590 m3
/s in July through August. In November, Gangetic Dolphin must have a minimum flow rate of
6020 m3/s, and in May and October, it must have an average flow rate of 9732 m3
/s. Ghorial habitat needs a minimum flow of 2978 m3/s in the month of February and a maximum flow
of 21325 m3/s in the months of August and September. The IFIM study was done for the
Carp and Catfish. The Catfish require a higher flow value than Carp in most cases. Lastly,
the BBM estimates 5363 m3/s of e-flow in the dry season. The minimum flow required for
fisheries dominates from November to April, and the flushing floods requirement
dominates from July to September. Therefore, the Jamuna River needs to flow at a rate of
roughly 5363 m3/s during both study years, 2005 and 2021. From holistic judgement, there
is enough water during dry seasons to sustain the riverine ecology, but no excess water
compared to the low flow analysis, where 90th and 50th percentile lowest flow values were
3725 m3/s and 4965 m3/s respectively. Recent trend in hydrological variations, particularly
during the dry seasons suggests meeting e-flow demands for Jamuna in the upcoming years
but regular use of excess water for consumptive purposes is less likely according to this study.
