Damming effects on trophic and habitat state of riparian wetlands and their spatial relationship

Abstract

Damming over the river remarkably alters the downstream hydrological and ecological state of the river and riparian wetlands. Considering this, the present work intended to explore the habitat quality and the trophic state index (TSI) of the wetland in Tangan river basin of India and Bangladesh. The spatial linkages between habitat quality and TSI was also assessed. Random forest (RF), Radial basis function neural network (RBF) and Artificial neural network (ANN) algorithms based habitat vulnerability models were constructed based on eight proxy data layers, which are mainly related to hydrology. The ANN and RBF models were found as the best representative. In the pre-dam period, about 30% area was under high and very high habitat vulnerability, while it was increased to 54% after damming. TSI value in the post-dam period was found significantly higher (44–54) in comparison to pre-dam phase (18–22). It was also identified that vulnerable habitat areas were more susceptible to poorer water quality. Hence, in water quality and ecosystem related data sparse conditions, the proxy parameters can be used effectively for habitat vulnerability modelling. Furthermore, results clearly demonstrated that damming has deteriorated the habitability and trophic state of the wetland. To restrain the growing impact, ecological flow maintenance to the dam downstream river and riparian wetland is essential.