Climate-changed versus land-use altered streamflow: A relative contribution assessment using three complementary approaches at a decadal time-spell

Streamflow, the key component of catchment-scale hydrology is acknowledged as being induced by climate change and land-use alterations. The potential quantification of these hydrological drivers on streamflow variations is quite challenging. This study quantitatively assesses the isolated influences of climate change and land-use alterations on the streamflow variations in the Brahmani (36,800 km(2)) and Baitarani (12,094 km(2)) River catchments of eastern India by applying three complementary techniques involving: (i) m-DMC approach (traditional trend analysis); (ii) m-SCARQ approach (slope change ratio approach); and (iii) SWAT-based hydrological modeling approach. The hydro-meteorological (precipitation, temperature, and streamflow) data variation and its significance are studied at a decadal time-spell followed by the Mann-Kendall test and the linear regression technique. The relative contributions of changing climate (theta(C)(ji)) and land-use alterations (theta(L)(ji)) are quantified at a decadal time-spell considering the initial time-spells as baseline periods (1979-1988, 1989-1998, and 1999-2008) and the subsequent time-spells as impacted periods (1989-1998, 1999-2008, and 2009-2018). Outcomes of our comparative assessment of the study area indicate that the empirical approaches (m-DMC and m-SCARQ) result in land-use alterations as a dominant contributing factor in streamflow variations. However, the performance of the SWAT-based hydrological approach specifies identical contributions from both the climate and land-use changes. The diversity in results from these three approaches is associated with different sources of errors and uncertainty. Thus, it is necessary to interpret the results of different separation approaches cautiously while addressing the adaptive management of a catchment for sustainable water resources planning in the future.