E-flow defines the quantity, timing and quality of water flow required to sustain freshwater and estuarine ecosystems, besides human livelihood.
A bench headed by acting Chairperson Justice U D Salvi issued notices to the ministries of Environment and Forest, Ministry of Water Resources, Central Pollution Control Board, National Mission for Clean Ganga, Uttarakhand Jal Vidyut Nigam Ltd and others while seeking their replies before March 8.
"Direct Respondent no 2 (Water resources) and Respondent no 4 (NMCG) to release into the main stream of the Ganga a minimum environment flow at all times of 'not less than 1/3rd the average virgin flow of the river in the wet period, but more than 40 per cent of the dry period' as suggested by IIT consortium," the plea said.
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The plea, filed through advocates Ritwick Dutta and Rahul Choudhary, claimed that substantial flow of the river Ganga was being diverted at Pashulok Barrage in Dehradun district to a side canal for a hydroelectric power plant of 144 Megawatt capacity.
"The diversion has led to sparse water flow in the main stream of Ganga downstream from the barrage flowing towards Haridwar and for majority of the year there is close to no water downstream of the Pashulok Barrage near Veerpur, Rishikesh," it said.
The tribunal had earlier directed all states to maintain a minimum environmental flow of 15 to 20 per cent of the average lean season course in their rivers.