Development of habitat suitability criteria for conservation of the black‐necked crane in Nyamjang Chu River in eastern Himalaya, India in connection with a proposed hydropower dam

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AbstractWe developed the habitat suitability criteria for the black‐necked Crane (BNC) to manage their wintering habitat in the Nyamjang Chu River in Zemithang valley, India. We generated habitat suitability criteria (HSC) curves for BNC based on the habitat availability in the river channel and use by the BNC. The HSC curves indicated that BNC preferred velocity ranged from 0 to 0.2 m/s and depth ranged from 0 to 30 cm in the river channel. Based on the HSCs of BNC, three scenarios were explored in PHABSIM: Scenario (i) increase in flow versus dry riverbed area; Scenario (ii) increase in flow versus instream suitable area; Scenario (iii) increase in flow versus weighted usable area based on combined dry and instream suitable area. The output of Scenario (i) indicated at 20 cumecs discharge achieved optimum dry riverbed area (47.07%) available for BNC, whereas Scenario (ii) predicted the different section of the river produced optimum instream area at different discharges. Though, the Scenario (iii) predicted at 20 cumecs discharge, the study area generated more than 57.38% of combined suitable habitat available for BNC. Since a proposed hydropower dam in the Zemithang valley is intend to raise water level in the river channel, it is expected to be reduced suitable habitat for BNC in the valley. Based on the PHABSIM output, we concluded that the availability of suitable habitat of BNC decreases steadily if the discharge flow increases above 20 cumecs. Moreover, the predicted average dry riverbed area (47.07%) at 20 cumecs was almost equal to the percentage of dry riverbed area (47.8%) that was naturally available during the winter. Thus, we recommend a maximum of 20 cumecs as ecological flows to maintain the minimum required habitats for wintering BNC in the Nyamjang Chu River. Consequently, the installation of the proposed dam in Zemithang valley may not be feasible.