Assessment and Implementation of Environmental Flows to Restore River Gomti- a Tributary of Ganga, India
Environmental flows in rivers are essential to maintain their natural regime, purify themselves, sustain aquatic life and vegetation, recharge groundwater and support livelihoods. Rivers play their role in people’s cultural and spiritual lives. These functions are possible with a suitable e-flow regime. This paper aims to quantify E-Flows for alluvial river Gomti- a tributary of river Ganga, at upstream and downstream of Lucknow City, at Sultanpur and at Jaunpur. These E-flow sites were chosen on the basis of homozonation study of Gomti Basin. Two methodsHydrological consideration and holistic approach: Building Block Methodology has been employed for assessing the Eflows at four sites falling in middle and lower zone of the Gomti Basin. The two set of E-Flows obtained have been compared with observed flows and virgin flows limits to visualize the implications of implementation plan for normal maintenance year and drought year. Considering Gomti basin water plan for 2045 while trying to meet future sectoral water demand and managing e-flows minimum allocation, the paper argues for e-flows implementation by participatory wetland conservation and improvise agricultural water use efficiency. Summary of investment plan in Gomti Basin to manage demand and supply of water optimally including minimum e-flows in Gomti river. Freed water from agriculture may be diverted into river Gomti from irrigation canal systems, offtaking from Sharda and Ghaghara rivers passing through the Gomti basin. It is found that recommended monthly E-flows for Mehndighat is higher than the observed flows and even more than virgin flow volume except in the month of July. At Fuslauna site E-flows are higher than estimated virgin and observed flow for the months of January to June and for rest of the months July to December, E-flows values are within virgin/observed flow volume limits. Hence to implement Eflows in Gomti river at Fusluana site, additional water from Sharda Sahayak Feeder, through Gomti escape has to be released for lean flow months January to June. Augmentation of flows in Gomti river is recommended by increasing base flows contribution particularly during lean flow months. For Sultanpur and Jaunpur sites required e-flows are almost twice higher than the present day flows in Gomti river. E-flows for Gomti river at Jaunpur is higher than the virgin flow for the month of January to June, estimated at Maighat - a d/s CWC site below Jaunpur. Alternatively, based on MOWR guidelines (as issued in case of Ganga river) considering only hydraulic perspective, minimum E-Flows for Gomti river at Lucknow, Sultanpur, Jaunpur and Maighat has been calculated. E-Flow estimates for Lucknow comes to 15.02 m3 /s, 7.70 m3 /s and 3.41m3 /s during monsoon (June to Sep.), non lean flow month (Oct & Nov.) and lean flow months Dec to May respectively. For Sultanpur site 42.70 m3 /s, 23.73 m3 /s and 10.26m3 /s and for Jaunpur site 44.94 m3 /s, 29.22 m3 /s and 11.28m3 /s has been obtained for the same period. E-flows assessed applying BBM, monthly discharge ranges are for Mehndighat 40-415 m3 /s, Aqueduct site 40-58 m3 /s, Sultanpur 92-950 m3 /s and for Jaunpur site 100-795 m3 /s. During wet months flushing requirement for two weeks period is 310 m3 /s at Lucknow, 1370 m3 /s at Sultanpur and 2450 m3 /s for Jaunpur. This peak flow appears possible at Lucknow due to barrage but difficult to implement at Sultanpur and Jaunpur . Although ever maximum discharge observed had been at Lucknow 916.97m3 /s, at Sultanpur 1373.68 m3 /s at Jaunpur 2991.82 m3 /s and at Maighat 3521.53 m 3 /s but on average and 75% dependability level these flow becomes very low. It is suggested that E-Flows assessed for Gomti river using BBM may be refined on the basis of more research carried out with informed hydrology, biodiversity habitat conditions and parameters of geomorphology.
