Exploring the spatial variability of contributions from climate variation and change in catchment properties to streamflow decrease in a mesoscale basin by three different methods

• We explored the spatial variability of relative contributions to streamflow decrease.
• We made a comparison study among three different attributing methods.
• Contribution of climate variability decreased from upstream to downstream.
• Spatial variability can be explained by growth rate of population.

SummaryThe hydrological response to environmental changes has attracted a lot of attention and a couple of methods have been used to quantify the relative contributions of climate variability and change in catchment properties to streamflow change at basin scale. However, few studies have been carried out to explore the spatial variability of the results at sub-basin scale. The aim of this study is to explore the spatial variability of relative contributions from climate variability and change in catchment properties to streamflow change within a mesoscale basin using three methods, namely elasticity and decomposition methods based on the Budyko framework, and the dynamic hydrological modeling method. The Upper Hanjiang River Basin (UHRB) is chosen as the study area, which presents a significantly decreasing trend of annual streamflow since 1990. We partitioned change in catchment properties into vegetation-induced change and non-vegetation-induced change in the hydrological modeling method, and climate conditions into precipitation and potential evaporation in the elasticity method. The results of the three methods suggest that climate variability is a greater contributor to streamflow decrease than change in catchment properties for the UHRB, whereas the relative contribution from change in catchment properties increases from 17% in the upper parts to 54% in the lower parts, which is likely linked to the population growth. The relative climate contribution estimated from the hydrological model is greater than these from the two Budyko framework based methods, and the estimated relative climate contribution from the decomposition method is the smallest in the three methods.