BHUBANESWAR: Bhitarkanika Wildlife Sanctuary could be poised for a significant rise in salinity levels and change in vegetation pattern across the crucial mangrove ecosystem, thanks to a projected drastic reduction in freshwater flow into the Ramsar site over the next few decades.
The hydro-ecological assessment report of the Ministry of Environment, Forest and Climate Change (MoEFCC) which used modeling systems to calculate fresh water supply to the sanctuary in the coming years says that future developments could seriously impact growth of the area.
The report says freshwater availability at Bhitarkanika sanctuary's boundary will be reduced by about 38-44 per cent (pc) during monsoon and 33-39 pc during non-monsoon. This might increase salinity level to a great extent.
Estimation is that a 50 per cent reduced water flow could mean salinity at Dangamal will match that of Gupti and vegetation at the former location will be replaced by vegetation of Sunirpuri block which has maximum saline species. The consequences could also be that Gupti will have Ekakula's salinity levels.
"Maximum impact will be observed at Dangmal or Bhitarkanika block and most of the freshwater species will, probably, get seriously impacted. However, a 20 pc decline in salinity will not have that alarming effect," says the report.
The key impact of reduced freshwater flow on mangrove health will be reflected through increased salinity and reduced flow of sediments which can have serious consequences on species composition.
Fresh water supply availability to Bhitarkanika, as per the report, could come down to 11,563 million cubic meter (MCM) by 2051 from 19,582 MCM in 2001. Interestingly, between 2001 and 2051, the inflow into river basins of Brahmani and Baitarani rivers would have seen only a marginal change - from 26,242 MCM to 25,068 MCM.
But, after use for agriculture, pipe water supply, evaporation, delta storage, industrial and local consumption, the drop would be from 74 pc of the availability in 2001 to 46 pc in next 30 years.
Sustainability of mangroves is dependent on a delicate mix of abundant freshwater and saline water which the tidal actions provide. Presence of salinity at adequate level is the most desirable condition and in the absence of optimum salinity range, mangroves would not survive.
Besides the indirect influence through loss of mangroves, salinity also directly impacts fish development and growth. Reduced freshwater flow may change the current dynamics, says the assessment report. As it is, the dense mangrove cover in Bhitarkanika has dropped over the years.
In 2002, it stood at 122 sq km, about 18 pc of the sanctuary. By 2020, it dropped to 101 sq km, reporting a 14 pc decline. Open mangrove, during the period, increased from 29.8 sq km to 49.5 sq km. Aquaculture, in the 20 years, jumped from 0.6 sq km to 19.5 sq km, registering a 47 pc rise, said the MoEFCC report.