Ecology, changes in fisheries, and energy estimates in the middle stretch of the River Ganges

Abstract

The River Ganges is the most important of all Indian rivers. It is being harnessed for several onsite and offsite benefits for various sections of society. Through varied man-induced interventions, over the years, the river system has recorded changes in its ecological functions, especially at some stations of the middle stretch viz., Kanpur, Varanasi and Allahabad. An attempt has been made in the present paper to understand changes with regard to key parameters of water quality, fish species composition and catches in this stretch, covering the highly populated major states of Uttar Pradesh and Bihar. For this purpose, data available over the years and some new data were utilized. These data reveal that siltation over the years has lowered water volumes and depths at various sections in the middle stretch with over 90% of the sediment comprising sand. The water quality in terms of pH remained higher (7.0 to 8.8) at some stations while dissolved oxygen remained lower (4.5 to 5.8 ppm) in comparison to upper and lower river stretches, suggesting progressive eutrophication. Other parameters, especially nutrients, also showed variations, coupled with variability in plankton density and primary productivity in this stretch reflecting changes in ecological functions. These changes coupled with various engineering interventions has resulted in drastic changes in water flows in the main river channel, the cumulative impact is evident in the drop in fish catches from 932 kg km−1 in the 1960s to 382 kg km−1 in the recent past, and the shift in species dominance from Indian major carps to less economic varieties. This has affected the livelihoods of fishers. The general lack of concern and awareness among the river authorities on requirements of river fishery management has been observed to be main reasons for these changes. Possible policy and governance interventions required to restore the river for sustainable fishery have also been suggested in this paper.