The ecological price of ‘progress’

Once the river’s course is changed, some highly endangered species will lose their habitat
«The White-bellied heron Photo: Yeshey Dorji
Punatsangchu Hydropower Projects: The endangered white-bellied heron, the great Indian hornbill and the endangered golden mahseer gaming fish found along the Punatsangchu river could come under great risk, once the Punatsangchu hydropower projects start operations.

As of now, the two projects, with an optimum generating capacity of around 2,150MW are still in the construction stage, and have not had much impact on these life forms as the river system has not been seriously disturbed.

“There is noise pollution, as of now,” a senior environment officer of Punatsangchu II project, Sangay Dorji, said.

But once the river is channeled in from dams to the underground powerhouses through the 8.9km headrace tunnel of phase I and 8.6km of phase II, the original river course will under go a massive change, Sangay Dorji said.

Mahseer

Environmentalists and conservationists are concerned on how to conserve the sensitive golden mahseer, which get distracted so easily. “When we try to use a net, they don’t show up for the next week,” Sangay Dorji, who led a sample study of the fish to understand its behaviour and habitat, said. “The fish may stop coming.”

The golden mahseer, found in Dichu, and at the confluence of the Punatsangchu and Kamechu streams, migrate to Brahmaputra, India, by the first week of October, and return in early summer.

The fish has been known to grow 2.75m (9ft) in length; but, so far, the biggest catch in Bhutan is said to be of the height of an average Bhutanese man.

Around the world, this species has suffered severe decline, because of overfishing, pollution and habitat loss. Environmentalists, this year, curved the Kamechu stream at the confluence to slow down the river current, so that the mahseer can easily lay eggs, and thereby grow in numbers.

Indian hornbill

The critically threatened white-bellied heron, seen along Kamechu and Punatsangchu rivers in Pinsa, will be affected when the Punatsangchu is dewatered, and only a small quantity of water remains its original course.  When the water quantity goes down, so will the fish, environmentalists said.  The bird feeds on the asla fish.

“In dewater stage, when the river undergoes a complete change, resulting in loss of aquatic ecology, the white-bellied heron will no longer be able to feed in its original place,” Sangay Dorji said.

Dark grey with a white throat and underparts, the heron is mostly solitary, and found in undisturbed areas of the riverside and wetland habitats.  The species is threatened by disturbance and habitat degradation.  It is believed that, out of 140 white-bellied herons across the globe, 26 are in Bhutan.

The great hornbill, another near threatened bird that nests in the evergreen forest and tall trees will lose its habitat, when roads, electricity, and housing colonies come up on both sides of the Punatsangchu.  Bright yellow and with a black casque on top of its massive bill, the bird feeds on small mammals, reptiles, birds and fruits.

The common otter found in Kamechu will also lose its source of food.  But since the mammal is mobile, the impact on it could be less, Sangay Dorji said.

Source Kuensel