Temporal Changes in the Effect of Damming on the Degree of Hydrological and Ecological Alteration in Floodplain River and Wetland

Abstract

The temporal changes in the effect of damming on the hydrological and ecological condition of a river and associated riparian wetland were examined in the present study. Does the degree of hydrologic and ecological alteration decline over time? Hydrological alteration was assessed in reference to the wetland water richness (WWR) modelling in three phases: pre-dam phase (up to 1992), post-dam phase 1 (1993–2012), and phase 2 (2013–2020). Periodicity of river flow at season scale was assessed usingthe wavelet transform model. The degree of ecological alteration was measured using a range of variability approach (RVA) and flow duration curve (FDC). From the analysis, it was revealed that after damming, the monthly flow failure rate increased (70–96%). The eco-deficit in the river was further exacerbated as the temporal distance increased. As a consequence of this, wetland water richness (WWR) maps of different phases exhibited continuous loss in the poor WWR parts. Eco-deficit condition of the wetland became severe in post-dam phase 1 and it was continued but with a lesser rate of increase in the next phase. The findings of this study would have significant implications for ecological flow management in rivers even after damming in order to continue eco-flow in downstream river reach and support riparian wetlands of immense ecosystem values. The study suggests conducting comparable studies with longer post-dam lengths in order to better determine how the effects of damming change over time.