Influence of climate and land-use changes on the sensitivity of SWAT model parameters and water availability in a semi-arid river basin

Abstract

The present study assesses the impact of climate change (CC) and land use land cover change (LULCC) on model parameter variability and alterations in streamflow and water balance components of a semi-arid river basin in western India. The Dharoi catchment in the Sabarmati River basin is a water-scarce region with India's lowest per-capita water availability. The water scarcity conditions are likely to aggravate due to changing climate and landscape modifications through human interventions. A hydrological modelling framework using a semi-distributed Soil and Water Assessment Tool (SWAT) is adopted in this study, considering two approaches: a variable-period calibration and a fixing-changing approach. Several model scenarios considered in these approaches are simulated through both single-site (SSC) and simultaneous multi-site calibration (SMSC) techniques. The variable-period calibration is adopted to assess the individual and combined influences of CC and LULCC on SWAT model parameter variability and change in water balance ratios. The fixing-changing approach evaluates the relative contribution of CC and LULCC to streamflow changes. The temporal changes in the hydroclimatic variables are analysed using non-parametric Pettitt, Mann-Whitney, Modified Mann-Kendall, and Spearman’s rho tests. The results indicated an abrupt increase in the streamflow in 2004, attributed to a significant increase in total and extreme rainfall magnitude and frequency in the catchment. The SSC and SMSC techniques yielded satisfactory and comparable performance for all model scenarios. The results showed that CC has a more significant impact on SWAT model parameter variability than LULCC. Thus, CC is the primary driver of streamflow changes in the Dharoi catchment, wherein a four-fold increase in the streamflow is noticed in the period 2005–2014 vis-à-vis 1995–2004. Thus, a transition from drier to wetter hydroclimatic conditions is evident in the Dharoi catchment, which would enhance water sufficiency in the region if appropriately managed.