Environmental flow estimation through a hydrology-based method in the Tamas River at Bakiya Barrage, Madhya Pradesh, India

Abstract

The River Tamas is a right-bank tributary of the River Ganga flowing through the states of Madhya Pradesh and Uttar Pradesh, India. It originates in Jhukehi village in the Satna district of Madhya Pradesh and after 268 km it joins with the River Ganga at Sirsa, Prayagraj, Uttar Pradesh. The river has a diverse habitat and harbours a variety of flora and fauna. More than 70 fish species reside in the river, along with other biotic communities. A barrage, named Tons and situated at Bakiya village, was commissioned in 1992 for hydro-electric purposes. The continuity and volume of water in the river have been disturbed due to the construction of this barrage and it has changed the ecology and biodiversity. Keeping the ecosystem intact requires that environmental flow calculations be made of the river at the barrage. An attempt has been made to estimate the environmental flow requirement using a desktop hydrological method. Based on the flow duration curve (a hydrological method of flow estimation), the environmental flow for the River Tamas has been calculated using Global Environmental Flow Calculator software. Our calculation are based on flow discharge data received from the Tons Barrage Authority at Bakiya for the period January 2006 to December 2017. Average annual discharge was calculated from the recorded maximum (151.46 cumecs in 2016) and the minimum, 13.53 cumecs in 2007. Mean Annual Runoff was calculated as 1607 Million Cubic Meter with Coefficient of Variation =0.799. To maintain the river in the “slightly modified” class of Environmental Management Class, 27.8 % of Mean Annual Runoff discharge should be released into the river to largely maintain the biodiversity and habitat, while about 57% of Mean Annual Runoff discharge is required to maintain this river in pristine condition. This is a preliminary study to determine the water requirements for healthy habitat and biodiversity of the Tamas river.