Long-term trends and projections of hydrological fluxes under RCP climate change scenarios for a mountainous river catchment of northeast India

Abstract

The estimate of changes in hydrological fluxes from a climate change perspective is inevitable for assessing the sustainability of watersheds and conserving water resources. Here, we quantify and assess the changes in different hydrological flux components for the Manu-Deo River Basin (MDRB) of northeast India using Soil and Water Assessment Tool (SWAT) simulations and multi-temporal data at various resolutions. Sequential Uncertainty Fitting (SUFI-2) optimization is used to calibrate and validate the simulations for the periods 1984–2006 and 2007–2016 and for the four future representative concentration pathway (RCP) scenarios. The model performed reasonably well for calibration and validation for daily data, in accordance with the Nash–Sutcliffe efficiency and coefficient of determination (0.54/0.55 and 0.52/0.72, respectively). The analysis for the period 1985–2013 reveals a decreasing trend in streamflow, which indicates increasing trends of drought there. Furthermore, it shows an increasing trend in evapotranspiration (ET) and decreasing trend for baseflow (BF), suggesting an adverse impact on agricultural production during lean periods. In addition, the RCP 2.6 and 6.0 scenarios for the monsoon season in future time scales are expected to cause a reduction in different flow components, although RCP 8.5 shows increased water availability there. The sub-basin-scale quantification and multi-temporal analysis of water availability under the present and future climate scenarios, as presented here, can assist water managers in formulating a suitable operational policy to implement a better decision-making framework for river and waterbody management. This is particularly important for mountainous regions, where input data are sparse and modelling of hydrological fluxes is challenging.