Author/s:

Talukdar, S.
Pal, S.

Publisher:

Springer Link

Year of Publication:

2017

Punarbhaba river basin of Indo-Bangladesh (5265.93 sq. km) is an evident example of hydrologically and ecologically modified river since 1992. One dam was installed over Dhepa River in 1992, which is main water supplier to Punarbhaba River at Birganj (25°51′46″N and 88°39′52″E) in Bangladesh. Since then, flow character of the river has changed as well as integrity of the environmental flow has also become modified. Average water level (W.L.) reduced during pre-monsoon and post-monsoon are 52.24 and 32.34%, respectively, to total depths of water in reference to pre-dam water depths, flow level fluctuation is 2–3% increased in post-dam condition. Range of variability calculated for different months and seasons indicates that in post-dam condition most of the cases water level did not cross even the lower flow threshold. It has serious impact on reliant ecological set up of the downstream course. Degree of impact due to hydrological alteration as indicated by indicators of hydrological alteration (IHA) value for maximum, minimum, and average discharges are 0.34, 0.40, and 0.39, respectively, which signify that the river is impacted in both upper and lower discharge ends. In dam after condition, ecodeficit (anthropogenic flow use exceeds flow requirement for the survival of the species) is a more stable feature which actually signifies emerging crisis in ecology. In rivers Punarbhaba and Tangon, 23.59 and 17.36% flood plain area has become squeezed respectively due to 44.59% attenuation of peak flood and such attenuation is responsible for water deficit to the flood plain wetlands.

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