Streamflow, the fundamental element of catchment-scale hydrology, is expressed as a complex response of many hydrological processes that includes atmospheric forcing (precipitation and temperature) and human activities (land-use change, reservoir/dam construction, and excessive water exploitation). Thus, change in climate variables and land-use alter a catchment’s streamflow pattern, which is a critical concern to the researchers. In the present study, the potential contributions of Climate Change (CC) and Land-use Conversions (LC) on streamflow variations are quantified for the Brahmani catchment (36800 km2) of eastern India. The estimation procedure is followed by two empirical approaches, i.e. (i) the modified Double Mass Curve (m-DMC) method and (ii) the modified Slope Change Ratio of Accumulative Quantity (m-SCARQ) method. The abrupt changes in streamflow data series are checked by the sequential Mann-Kendall method. Multiple change points, including 1981, 1985, 1993, 1994, 2011, and 2013 are observed in streamflow data series in the study area. However, 1994 is selected as the break-point, which has the highest significance value, i.e. 1.92. Therefore, the entire analysis period (1979-2018) is divided into two sub-periods, i.e. the baseline period (1979-1994) and the assessment period (1995-2018). Further, the statistical characteristics (trend, slope, and significance) of hydro-climatic variables (precipitation, temperature, and streamflow) are analysed by applying the Mann-Kendall method followed by the Sen’s slope estimator for all the periods. Using the m-DMC method, the potential contributions of CC (βCC) and LC (βLC) in the assessment period are quantified as 93.09% and 6.91%, respectively. However, from m-SCARQ, the contributions of precipitation (βP), temperature (βT), CC (βCC), and LC (βLC) on streamflow variations are 0.26%, 19.74%, 20%, and 80%, respectively. The outcomes of the m-DMC other than the m-SCARQ method showed that streamflow variation is more sensitive to climate change of the study area. Further, the m-SCARQ method is relatively strategic compared to the m-DMC method since it can signify the contributions of precipitation (βP) and temperature (βT) on the streamflow variations. Still, both the empirical approaches are attributed to different sources of errors and uncertainty with individual advantages. Accordingly, this study can provide new insights concerning the relative resistance of the Brahmani catchment’s response to CC and LC that is vital for the prudent planning and management of future water resources. Keywords: Climate change; Land-use conversions; m-DMC method; m-SCARQ method; Brahmani

Water Balance Components (WBCs), the most fundamental processes of a river basin, are getting disturbed by climate change and land-use alterations in the present scenario. These two factors are the major driving force behind the spatio-temporal variation of the WBCs that creates an alarming concern for fulfilling water demand by different sectors. The popular hydrological model Soil and Water Assessment Tool (SWAT) is applied to the Baitarani River basin (12,095 km2) of eastern India for evaluating the dominance of the above factors on the WBCs deviations at a decadal scale (1980-1989, 1990-1999, and 2000-2009). A quantile regression-based stochastic approach has been used to analyze the uncertainties resulting from different simulations accounting the combined responses of climate change and land-use alterations as well as model parameters. However, such analysis has not been explored more for the present study area. The model performance results reveal that the statistical performance indices (NSE and R2) are within the acceptable limit. The WBCs in terms of evapotranspiration, surface runoff, lateral flow, water yield, soil moisture storage, and deep aquifer recharge has been quantified at a decadal scale from the simulated model outcomes. The result shows that the water yield component is more (680.36 mm) for mid-decade (1990-1999) as compared to other decades, which is favourable to fulfill sectoral water demand. Further, the uncertainty analysis explains that climate change impact plays a vital role in WBCs variation. The developed approach can portray the variability of WBCs of other river basins that are vulnerable to climate change. The outcomes of this study can be used to maintain an appropriate balance between water availability and demand to avoid water scarcity. Keywords: Water balance components; Climate change; Land-use Alterations, Brahmani; Baitarani